ASTRONOMY AND ASTROPHYSICS

Table of contents :

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Milky Way galaxy space vehicles space tourism Big Bang g-ray bursts telescopes comets antrigravity supernova exobiology

the solar systems Sun Earth Moon Mars Saturn Titan extrasolar planets black holes

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• Wherever matter concentrates in the vast vacuum of space, chances are you will find a disk. Simple physics makes it so; all you need is a spinning sphere of matter collapsing under its own gravitational pull. As the core contracts, it rotates faster to conserve angular momentum. This spin causes the matter around the core to fall onto the equatorial plane, forming a flattened disk of gas and solids. Angular momentum creeps outward, keeping the core from breaking apart. Meanwhile, disk material moves inward along the equatorial plane, eventually either feeding the core or forming other orbiting objects around the core. That oft-repeated scenario makes disks essential building blocks of the universe. This special section covers the many different flavors of disks in space and what they can tell us about the formation of everything from giant gas planets to galaxies. The solar system got its start when a molecular cloud collapsed to form the Sun and a circumstellar disk of gas and dust. Chondritic meteorites contain primordial dust from other nearby stars, evidence that the Sun formed within a cluster of stars^ref. At the edge of the solar system, where remnants of the circumstellar disk are dispersed in the Kuiper belt. The belt is more extensive and more structured than previously thought, and its structure holds clues to planetary formation, planetary migration, possible rogue planets, and the close passage of other stars^ref. Over the past decade the search for circumstellar disks with possible planets around other stars has intensified. Planets around Sunlike stars are now considered to be ubiquitous^ref. Current models of planet formation require a disk full of gas and dust to swirl and sway around the star long enough to accrete giant gas planets. Observations of the different stages of the evolution of circumstellar disks are helping to refine these models. For decades, astrophysicists thought that disk-shaped spiral galaxies turn into featureless balls of stars when they collide with other galaxies. The spirals (which include our own Milky Way galaxy) can be surprisingly resilient^ref. Meanwhile, other astronomers are probing how disks of matter pulled from a companion star trigger the nuclear explosions that turn white dwarf stars into type Ia supernovas^ref: cosmic flares that help gauge the expansion of the universe. The most illuminating evidence for black holes is the accretion disks that surround them^ref. As a black hole accretes gas, the gas radiates and provides a thermal signature of the mass, rate of spin, and location of the event horizon of the black hole. This quick tour of disks in space highlights their simplicity and ubiquity. As modeling and observations continue to provide more details of disk complexity, their utility for resolving fundamental mysteries of space, such as planet formation and black hole jets, will grow.
• Our Milky Way galaxy looks quite different from an ordinary spiral galaxy, astronomers say, after conducting what they call the most comprehensive structural analysis ever done of the galaxy. The Milky Way is no ordinary spiral galaxy. According to a massive new survey of stars at the heart of the galaxy, the Milky Way has a definitive bar feature -- some 27,000 light years long -- that distinguishes it from ordinary spiral galaxies, as shown in this artist's rendering. The small yellow arrow points to our Sun. The survey sampled around 30 million stars to build a portrait of the galaxy's inner regions. The survey gives fine details of a long, central bar feature that astronomers say distinguishes the Milky Way from more usual spiral galaxies. This is the best evidence ever for this long central bar in our galaxy. Using NASA’s orbiting Spitzer Space Telescope, astronomers surveyed some 30 million stars in the plane of the galaxy in an effort to build a detailed portrait of the inner regions of the Milky Way. The task is like trying to describe the boundaries of a forest from a vantage point deep within the woods: this is hard to do from within the galaxy. Spitzer’s capabilities, however, helped the astronomers cut through obscuring clouds of interstellar dust by gathering infrared light, a type of light which penetrates these clouds. This provided information on tens of millions of stars at the center of the galaxy. The new survey gives the most detailed picture to date of the inner regions of the Milky Way. We’re bringing tens of millions of objects into the equation. The possibility that the Milky Way Galaxy has a long stellar bar through its center has long been considered by astronomers, and such phenomena are not unheard of in galactic taxonomy. They are clearly evident in other galaxies, and it is a structural characteristic that adds definition beyond the swirling arms of typical spiral galaxies. The new study provides estimates for the size and orientation of the bar that are far different from previous estimates. It shows a bar, consisting of relatively old and red stars, spanning the center of the galaxy roughly 27,000 light years in length. This is 7,000 light years longer than previously believed.  The analysis also suggests the bar is oriented at about a 45° angle relative to a line joining the sun and the center of the galaxy. Astronomers have debated whether a presumed central feature of the galaxy would be a bar structure or a central ellipse—or both. The new research clearly shows a bar-like structure. To date, this is the best evidence for a long bar in our galaxy. It’s hard to argue with this data. The Spitzer Space Telescope went into orbit in August, 2003. NASA’s Jet Propulsion Laboratory in Pasadena, Calif., manages the telescope (Benjamin, Astrophysical Journal Letters)
• The cold dark matter model has become the leading theoretical picture for the formation of structure in the Universe. This model, together with the theory of cosmic inflation, makes a clear prediction for the initial conditions for structure formation and predicts that structures grow hierarchically through gravitational instability. Testing this model requires that the precise measurements delivered by galaxy surveys can be compared to robust and equally precise theoretical calculations. Here we present a simulation of the growth of dark matter structure using 2,160³ particles, following them from redshift z = 127 to the present in a cube-shaped region 2.230 billion lightyears on a side. In postprocessing, we also follow the formation and evolution of the galaxies and quasars. We show that baryon-induced features in the initial conditions of the Universe are reflected in distorted form in the low-redshift galaxy distribution, an effect that can be used to constrain the nature of dark energy with future generations of observational surveys of galaxies^ref.
• gravitational lensing : warped space seems to magnify light as well as bending it, in just the way that Einstein predicted, scientists have found. The discovery of a slight brightening of 200,000 distant quasars finally confirms a theory posited by Einstein > 90 years ago. According to Einstein's picture of the Universe, mass warps the fabric of space that surrounds it. Light from a distant star travels in a straight line along this fabric, but because it is slightly bent around heavy objects such as galaxies, the star's position when viewed from Earth is shifted^ref. This effect has been confirmed many times through observation. But bending light is only part of the story. Lenses also magnify images, and astronomers have been searching for a cosmic magnification of distant objects for decades. No one had been able to reliably detect the magnification part of the lensing signal. Scranton led the project from the Apache Point Observatory in Sunspot, New Mexico, which is the base for a broader project called the Sloan Digital Sky Survey (SDSS). Their results, which show a brightening of distant objects on the order of 1%^ref. The discovery also confirms that the Universe is full of dark matter. > 80% of the mass in the Universe is thought to be dark matter, the unseen material that seems to hold galaxies together. The amount of magnification seen by the SDSS team ties in perfectly with the predictions of current dark-matter models. The quasars observed by the SDSS project are about 10 billion light years away. Quasars are amongst the brightest objects in the Universe, and are thought to be distant galaxies that have a supermassive black hole at their centre. As matter accelerates into the black hole, it sends out powerful beams of radiation that can be seen from Earth. Quasars are an ideal way to watch for cosmic magnification, because they are distant enough to have their light bent by many massive objects before they reach Earth. Light travels to us on a very bumpy road from these quasars. They also produce enough light for scientists to measure small changes in their brightness very precisely. Previous groups have been able to measure the brightening of a much smaller sampling of quasars. But those results showed a brightening that was too large to fit with either Einstein's ideas or the dark matter model. This led many to think the results were skewed by errors in the sensitive measurements. Now that seems to have been cleared up. This measurement agrees with what the rest of the Universe is telling us, and the nagging disagreement is resolved. Using a huge sample of quasars was the key to ironing out these errors. The team hopes to use cosmic magnification to study how galaxies and dark matter interact with each other.


• it's a hard life being the fastest star in the galactic suburbs. One minute you're waltzing around your companion, the next you're flung outwards by a black hole so fiercely that you're all set to be the first star to leave the Milky Way. "We have never before seen a star moving fast enough to completely escape the confines of our Galaxy," says Warren Brown, part of the team at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who spotted the 700 km/s star. It is the swiftest star ever spotted in the outskirts of our galaxy, travelling at twice the speed needed to escape from the Milky Way. Runaway stars have been seen before, but the previous record-holder was seen travelling at a mere 490 km/s, and all of them are still confined in our Galaxy. The new speedster is called SDSS J090745.0+024507, but researchers were tempted to call it the outcast star^ref. The astronomers believe that the star once had a companion. But as the pair twirled around each other they waltzed too close to the Milky Way's central black hole and the companion was trapped there, flinging the outcast away like a stone from a slingshot. The star is rich in elements heavier than hydrogen and helium, making it characteristic of stars formed in the central regions of the Milky Way. The star is now in the outer reaches of the Galaxy, almost 200,000 light years from Earth, and is moving directly away from the Galactic Centre. The scientists believe that it has been on its present course for < 80 million years; it may be 80 million more before it clears the edge of the Galaxy and hurtles into intergalactic space. The team used initial observations from the Sloan Digital Sky Survey to spot potential high-speed candidates, and then tracked them with the Multiple Mirror Telescope, perched atop Mount Hopkins near Tucson, Arizona. Almost 20 years ago, Jack Hills, an astronomer at Los Alamos National Laboratory in New Mexico, proposed that this galactic slingshot mechanism could create 'hypervelocity' stars. There may be up to 10,000 more hypervelocity stars in our Galaxy. If dozens of these stars were tracked, astronomers could learn about the rate of star formation in the core of the Milky Way. Plotting their trajectories accurately could reveal the gravitational influence of hidden dark matter in the Galaxy
• the Universe's first stars were born a mere 700 million years after the Big Bang, far earlier than researchers previously thought. The discovery comes from images of stars in galaxies that are so far away their light has taken some 13 billion years to reach us. What's more, the images show that these early galaxies were surprisingly heavy, with as much as a quarter of the mass of galaxies that developed later, such as our Milky Way. Using NASA's Spitzer Space Telescope to collect infrared radiation from 2 of the most distant galaxies known, both found in the constellation Fornax in the southern skies, given the Universe's estimated age of 14 billion years, the team deduced that the galaxies look the way they did just a billion years after the Universe came into being. This is the first time that old stars have been seen in such a distant object : the stars in the images are already well developed. The stars are about 300 million years old in the images, meaning that they were born when the Universe was just 700 million years old. The orbiting Spitzer Space Telescope, launched in 2003, is the first telescope sensitive enough to allow an analysis of the infrared radiation from these stars. The galaxies' masses were estimted by comparing their spectra with models of spectra from galaxies with a known number of stars. Popular models of galaxy formation assume that the early Universe contained only very small galaxies, so this will cause theorists to think very hard, but such large galaxies could be the exception rather than the rule. Numerous lower-mass galaxies are predicted at the same epoch. Because large galaxies might be the only objects visible at great distances, there could be many smaller galaxies going undetected. That question may be settled by NASA's James Webb Space Telescope, which is much more sensitive and scheduled for launch in 2011.
• The birth of stars involves not only accretion but also, counter-intuitively, the expulsion of matter in the form of highly supersonic outflows. Although this phenomenon has been seen in young stars, a fundamental question is whether it also occurs among newborn brown dwarfs: these are the so-called 'failed stars', with masses between stars and planets, that never manage to reach temperatures high enough for normal hydrogen fusion to occur. Recently, evidence for accretion in young brown dwarfs has mounted, and their spectra show lines that are suggestive of outflows. Spectro-astrometric data have been reported that spatially resolve an outflow from a brown dwarf. The outflow's characteristics appear similar to, but on a smaller scale than, outflows from normal young stars. This result suggests that the outflow mechanism is universal, and perhaps relevant even to the formation of planets^ref.
• Andromeda, the nearest large galaxy, has been found to be almost 3 times wider than astronomers thought. Previous estimates had suggested that the spiral galaxy, also known as M31, was about 75,000 light years across. That is slightly smaller than our own galaxy, the Milky Way, which is 100,000 light years wide. But a project to map the movement of about 3,000 stars in Andromeda's distant outskirts has found that, surprisingly, they too are orbiting the galactic centre in the same plane as the rest of the galactic disk. Because this movement makes them members of Andromeda's stellar posse, astronomers have redrawn its perimeter to include them, boosting the galaxy's diameter to more than 220,000 light years. This will force theorists to reassess how such galaxies form. This discovery will be very hard to reconcile with computer simulations of forming galaxies. Within the boundary of a galaxy, matter orbits the galactic centre in an orderly disk. But Andromeda has an extended, clumpy halo of stars that are thought to have been left in the neighbourhood by galaxies that passed by and collided with its outer stars. Astronomers assumed that the force of these collisions would have left these stars buzzing around in random directions, and so didn't count them when measuring the galactic diameter. To check, researchers used the Keck telescopes in Hawaii to observe these stellar outsiders. Andromeda is the most remote astronomical object normally visible to the naked eye. It lies about 2 million light years from Earth. On one side of Andromeda's disk, light from the stars is redshifted: it is stretched to longer wavelengths as they move away from the Earth. But on the other side, the stars' light is blueshifted to shorter wavelengths as they move towards us. By calculating the difference between the shifts, the astronomers conclude that the outer stars are actually orbiting around the centre of the galaxy, and are therefore part of it. The clumps of outer stars left from galactic collisions should not, according to current models, get roped into Andromeda's disk. You just don't get giant rotating disks from the accretion of small galaxy fragments. Similar observations of other galaxies should be made to work out if this sort of extended disk is unique to Andromeda^ref

Web resources : Scott Chapman's Andromeda page
• Researchers have snapped a picture that catches a star in the act of capturing material from its companion. The image shows a bridge of gas streaming from a red giant, called Mira A, towards a nearby collapsed white dwarf, called Mira B. Researchers had a good idea that the white dwarf was probably sucking up material cast off from Mira A by its own stellar wind. But the visible bridge of material between them indicates that the white dwarf is also capable of snatching material straight out of the heart of Mira A. The bridge shows that there's actually matter flowing from the red giant towards the red dwarf.  Scientists at NASA's Chandra X-ray Observatory in Cambridge, Massachusetts, used information from the Hubble Space Telescope to locate this star system, which lies 420 light years from Earth. The stars sit about 6 billion km apart from each other, which is roughly twice the distance of Pluto from the Sun. The picture reveals X-ray radiation, rather than visible light. X-rays are produced by the star system as rapidly moving gas particles collide in the stream between the 2 stars^ref.
• We'll never find a star larger than about 150 times the size of our Sun, according to observations of a star cluster at the centre of our Galaxy. Astronomers have previously been unable to agree whether stars have a natural limit to their size, or what that limit might be. Theoretical estimates based on the turbulent dynamics of stars' guts have ranged from 10 to 1000 solar masses. The stars of the Arches cluster, discovered in the early 1990s, collectively have about 11,000 solar masses, making it the most massive star cluster in our Galaxy. If there were no limit to how big stars can grow, you'd expect ones up to 500 times our Sun's mass to be found in this dense cluster of stars. But no stars larger than about 130 solar masses was found. Mindful of limits to the accuracy of these observations, a reasonable upper limit to a star's mass is about 150 solar masses. This results indicates there is only a 1 in 100 million chance that stars have no upper limit to their mass. A galaxy's mass is estimated from the amount of light it produces, but this requires an assumption about the size distribution of its stars. That assumption often changes with each new theoretical treatment of the problem : at least now there is a firm number based on evidence. Although astronomers have claimed to see more massive stars, they always turn out to be a group of stars, or have huge uncertainties about their mass. A star > 150 solar masses could possibly exist briefly if 2 other stars collide. But of course this is a very violent process, and it's not going to live very long. A similar cut-of was found in a more distant star cluster, although that result was less statistically significant. Theoreticians should now focus on working out why stars have this mass limit In the late 1910s, the English astronomer Arthur Eddington suggested that growing stars might reach a point where the pressure of radiation coming from their cores was greater than the gravity keeping the outer layers held fast. At this point, stars could accumulate no more material, putting an upper limit on their mass. Alternatively, turbulence in the outer atmosphere of the largest stars could be enough to throw off material faster than fresh matter can accrete. The latest theoretical estimates from this model put the star's upper limit at around 120 to 150 solar masses, agreeing with this experimental observations^ref
• space vehicles
• Europe's reputation for rocket engineering got a boost with the successful launch of the Ariane 5 ECA at 21:03 GMT on 12 February 2005. The 50-metre high rocket is Europe's largest, able to deliver up to 10 tonnes of payload into orbit around Earth. But its maiden voyage on 11 December 2002 ended in disaster when the vehicle veered dangerously off course and self-destructed just minutes into the flight. The successful flight means that the ECA, operated by the company Arianespace of Courcouronnes, France, should begin to attract commercial customers. Each flight can carry several satellites into orbit, reducing the costs of each instrument's launch substantially. The first commercial flight is expected within the next 6 months. The ECA will replace the Ariane 5G 'generic' rocket, which is limited to carrying one satellite at a time. The ECA carries more fuel, and has had each of its engines beefed up: the main stage produces up to 20% more thrust. The rocket carried 3 different payloads on this launch. After 26 minutes of flight, the Ariane 5 ECA released a 3,600-kilogram communication satellite called XTAR-EUR into orbit. 2 other satellites built by the European Space Agency were also on board. One is called Sloshsat-FLEVO (Facility for Liquid Experimentation and Verification). This 129-kg craft is designed to help us understand how spacecraft can be destabilized by liquid fuel sloshing around inside their tanks in microgravity. The third satellite, Maqsat B2, was not deployed by the rocket. Instead, it provided an extra 3.5 tonnes of weight to prove ECA's lifting capabilities, and sent essential data about the whole flight back to mission controllers

Web resources : Kourou Spaceport
• Pioneer 10 and 11 were launched in 1972 to explore Jupiter and Saturn. After their studies there were done, they continued on towards the edge of the Solar System. But since around 1980, when they passed beyond the orbit of Uranus, the radio signals that they send back to Earth have been shifted to progressively shorter wavelengths, implying that the spacecraft are decelerating very slightly on their outward journey. It could just be some unforeseen effect generated onboard the probes themselves, by leakage of gaseous fuel from the thrusters, for example. But if it is not, then this deceleration (dubbed the Pioneer anomaly) might point to a gap in our understanding of the fundamental principles of physics. It could reveal the influence of a new force, or perhaps a new kind of matter. That would be a revolutionary finding, but even the more mundane explanation of an onboard instrumental effect would be very important because it would force space engineers to rethink their methods for very precise navigation in space. Sending a mission after the Pioneer craft would allow scientists to confirm whether the Pioneer anomaly is real, and to rule out some of the technological explanations^ref. The mission would need to have very accurate navigation, and instruments that could detect the tiny deceleration and potential causes such as leaking gas. And to get an answer in the next couple of decades would take a fast-travelling probe, one faster than the Cassini spacecraft currently orbiting Saturn. That planet is only half as far away as Uranus, but it still took Cassini 7 years to reach its destination. Instead of relying on conventional rocket fuel, the craft might use the faster propulsion systems being investigated by NASA and the European Space Agency (ESA), which involve nuclear power. The first of these craft is likely to be NASA's Jupiter Icy Moons Orbiter, scheduled to launch around 2015. But none of the currently proposed missions could probe the Pioneer anomaly as they stand, because they will not have sufficiently accurate navigation or instruments. So the researchers are arguing for a spacecraft that draws on the lessons learnt from the Pioneer missions, in which various accidents of design have made it possible to track the spacecraft's movement very closely. It could be developed in 5 years and flown early in the next decade. Adding instrumentation to missions already planned might be a more realistic option, which could cost as little as US$70 million. Both Pioneer spacecraft are now too far away for their weakening communications systems to make further contact with Earth. Pioneer 10 was last heard from in early 2003, and is now > 12 billion km away. It is heading for the giant red star Aldebaran in the Taurus constellation, but it won't get there for another 2 million years.
• scramjet (supersonic-combustion ramjet) engines, which, like a conventional jet engine, burns fuel using air sucked in from the atmosphere. In conventional engines the fuel cannot burn properly at high speeds because the oxygen whips by too quickly. Ramjets use the speed of the craft to compress air and heat it up, allowing their hydrogen fuel to burn more quickly. But scramjets only work when the craft is travelling faster than sound, making it difficult if not impossible to test in the lab : $230-million Hyper X programme
• scientists from the University of Queensland made a successful scramjet test flight in 2002 with a project called Hyshot. Their rocket did not have any wings, making it easier to control at speeds of Mach 7, but ultimately impractical for use in a vehicle. Although scramjets travel at immense speeds, they are not appropriate for most applications. The engines heat up to about 1000ºC. And craft travelling at that speed need hefty additional insulation to withstand the heat from air friction. Sonic shock waves also tend to reduce lift at high speeds, making it hard to keep the jet airborne. Put all these problems together and hypersonic flight just does not look like a good commercial prospect : we won't see passenger flight using this technology
• NASA's X-43A experimental unmanned aircraft :
• in June 2001, was blown up by flight engineers when they lost control of the craft shortly after it was released from the aeroplane
• on Sat Mar 27 2004 it flew under its own power for 10", reaching speeds > 2 km/s = Mach 7, or 7 times the speed of sound. The previous record-holder for jet-propelled flight was the US military's SR-71 Blackbird, which flew at 3.3 times the speed of sound. The X-43 A looks more like a missile than a plane, being too small to carry a passenger. The 3.6 m by 1.5 m jet was flown by remote control from the ground : an aeroplane carried the craft to an altitude of 12,000 m, from where it was lifted to 30,000 m on the back of a booster rocket. Once set free, it screamed through the atmosphere under its own power for 10". After a further 6' of gliding, it splashed into the Pacific Ocean. Rocket boosters can already travel much faster than Mach 7, but they must carry both their fuel and a source of O₂, reducing their cargo capacity and making them unlikely to be of use to a plane.
• on Nov 16 2004, it flew at nearly 10 times the speed of sound, breaking its own speed record. The unmanned X-43A aircraft reached speeds of roughly 11,000 kilometres per hour, flying under its own power for about 20 seconds. The X-43A was strapped to a Pegasus booster rocket and carried from Edwards Air Force Base, California, under the wing of a B-52B aeroplane. The plane released its cargo at an altitude of about 12 km, and the booster rocket blasted the craft up to 33.5 km. At this point the X43-A was already travelling at about Mach 9, then the booster fell away and the craft accelerated to close to Mach 10 using its own engines. It eventually travelled for > 1,000 km before splashing into the Pacific Ocean. Its flight had been delayed on Nov 15 while engineers made last minute adjustments to onboard instruments. The X-43A is little more than an engine with wings, and is 3.7 m long by 1.5 m wide. Unlike conventional jet engines, a ramjet engine uses its own speed, rather than rotating blades, to force air into its combustion chamber, where the oxygen reacts with hydrogen fuel. And in a scramjet, such as the X-43A, this combustion happens when air is forced in at supersonic speeds. This means that the engine only begins to work past Mach 4, making ground-based tests virtually impossible. Although NASA's rockets can fly faster than the X-43A, they must carry both hydrogen and oxygen, a combination that would be too risky and expensive for a commercial plane and that also reduces the craft's cargo capacity. Once ignited, rockets tend to burn continuously at full thrust, but the X-43A's engine can varying its power, allowing it to fly more like an aeroplane. Some engineers believe that scramjets could eventually allow passenger aircraft to fly around the world in just a few hours, although it would take decades of further research to achieve this. Still, in the near future scramjets might be adapted to deliver cargo into low Earth orbit. The Hyper X programme itself has been scrapped, however, since NASA's efforts were redirected to manned space flight after President George W. Bush outlined his 'Vision for Space Exploration' in January 2003. Engineers will now focus on building a replacement for the space shuttle fleet, due to be phased out in 2010
Web resources :
• Dryden Flight Research Centre (DFRC) - HyperX
• NASA's Hyper X project
• US History of Hypersonic Flight
• NASA: First Supersonic Flight
• Centre for Hypersonics
• return and rescue space systems (RRSS) : an inflatable lifeboat could one day ferry stranded astronauts back to Earth. The re-entry vehicle weighs just 130 kg and is being developed to carry cargo back from the International Space Station (ISS), but its inventors believe that it could also let astronauts bail out of the space station, or deliver robots to the surface of Mars. Inflatable spacecraft are not a new idea - NASA developed one in the 1960s - but they have never seen active duty. RRSS's craft, which has so far taken US$2 million and 6 years to develop, has been tested twice before, in 2000 and 2002. In the last test, the pod failed to detach from its rocket; the craft has been redesigned to solve this problem. The latest prototype will launch on a rocket from a Russian submarine in the Barents Sea off Murmansk. At about 200 km up (the equivalent of a low-Earth orbit) the ship will detach and inflate, then spend 200 or so falling to Earth, eventually landing, the team hopes, on Russian soil in Kamchatka. The demonstration vehicle is shaped like a shuttlecock, and is just over 3 m across. It carries pressure sensors and other equipment to monitor its descent. It will inflate using tanks of nitrogen, but RRSS hope eventually to use the same chemical reaction used in car airbags, which generates nitrogen gas from a powder. An inflatable heat shield will protect the ship and slow it down. A second, larger inflatable emerges from the rear of the craft to act as a parachute, reducing its speed to about 35 kilometres per hour before it hits the ground. The surface is made from a tough, flexible polymer coated with a paint that can withstand temperatures of around 900 °C. The exact composition of the paint is a closely guarded secret. The lifeboat could not help astronauts escape a stricken space shuttle, as the shuttle's design would prevent it launching. It may, however, be incorporated into the next generation of vehicles to replace the shuttle, and is one of several possibilities being considered by NASA.
• a metallic mutt, nicknamed Boudreaux, is officially called the Extra Vehicular Activity Robotic Assistant. It runs on 4 wheels and is about the size of a small golf cart, similar to the Mars exploration rovers Spirit and Opportunity. Tests conducted in the middle of the Utah desert in April 2004 proved that Boudreaux can follow a pair of astronauts at walking pace, carrying tools, geological samples or analysis equipment for them. It is nearly autonomous, able to plan a route for itself through rocky areas, but it also responds to voice commands, obediently trundling over to where an astronaut is working. It can even tell the astronauts where it is. With stereovision cameras to relay pictures of the astronauts back to a control centre, it will also allow mission commanders to keep a watchful eye on interplanetary explorers. Boudreaux has a dextrous arm that can pick up rock samples or dropped tools, tasks that are tricky for an astronaut wearing a bulky, inflexible space suit. On a long mission, the robotic dog would also be a lighter load for a spacecraft than a human with accompanying gear. Its tracking system currently works using a global positioning system (GPS), so the astronauts would need orbiting satellites on whatever planet they visit for the rover to work best. But as a back-up, Boudreaux can also use on-board cameras to navigate. As it could be 15 years or more before humans return to the Moon, Boudreaux will be ready to go into space before we are. The robotics team at Johnson Space Centre are better known for Robonaut, a humanoid robot designed for space walks that was unveiled in 2000.
• The Russian-built oxygen generator in the International Space Station (ISS), called Elektron, mysteriously shut down on 8 September 2004. The current crew, American Mike Fincke and Russian Gennady Padalka, have been unable to get it going again for more than a few hours at a time, despite numerous salvage attempts. NASA stresses that Fincke and Padalka are not in immediate danger. They have back-up oxygen, in the form of spare canisters and oxygen-releasing 'candles', to last another 140 days, which is long beyond their scheduled return. But the Elektron unit's failure opens up the possibility that the next crew in line, US astronaut Leroy Chiao and Russia's Salizhan Sharipov, will not get the chance to replace the current team. If that happens, the space station may never be fit to live on again. If it is not continuously inhabited, its habitability is seriously damaged. If the station was left uninhabited, space scientists could be left with their research plans in ruins. The space station was conceived as an orbiting lab that would play host to a range of scientific experiments. But because of setbacks, not least the Columbia shuttle disaster in February 2003, the station is staffed by a skeleton crew who can do little more than day-to-day maintenance. Denied its primary transport vehicle since the crash, the space station currently relies on Russia's Soyuz capsules to ferry crew and on Progress vessels to deliver cargo. Neither has the carrying capacity of the shuttle. The European Space Agency's Columbus lab module, for example, is still awaiting launch and is now in danger of never making it into space at all. But the aftermath of the shuttle disaster is not the only reason for the station's difficulties : the United States may be turning its back on the space station, even if it overcomes its current problems. President George W. Bush has famously announced that he wants to see an American on Mars, a plan that would not involve the space station. The plan seems to be to phase out the space station by 2010 or thereabouts. If the United States wants to get to Mars, it will need to start by developing a fresh programme to go to the Moon, bypassing the stranded station on the way. If the United States does give the space station the cold shoulder, its collaborators including Russia, Japan and Europe will not be impressed. They have all spent vast sums on the project, and would not appreciate being left in the lurch
• an experiment aboard the International Space Station will check the theory that imminent earthquakes can be spotted from space. Researchers hope that tracking changes in the radiation belts that blanket the globe will give them early warning of tremors hundreds of kilometres below. If successful, the work could help pave the way for a system of satellites that watch for earthquakes. Seismologists know that the rumblings that precede an earthquake cause disturbances across a wide range of frequencies that can be picked up by radio antennae. These disruptions are thought to result from the opening of tiny cracks in the rocks as they begin to deform. Monitoring these effects on the ground would require a huge, global network of antennae. Fortunately our planet has a natural version of such a net: bands of charged particles trapped in Earth's magnetic field, called Van Allen belts. These belts are best known for shielding the atmosphere from cosmic radiation. Electromagnetic disturbances may be detectable in the Van Allen belts before an earthquake occurs. The study is called Lazio-Sirad. But no one has yet been able to show that the effect can be spotted within the useful time frame of a few hours before an earthquake. The International Space Station, cruising some 370 km above Earth, grazes the lowest Van Allen belts at certain points in its orbit, providing a useful vantage point for observation. The Lazio-Sirad experiment will monitor the number and direction of charged particles in these belts for at least one week, and possibly for up to 6 months. They will then try to correlate variations in this particle flux with natural events. Slow variations are expected to be caused by solar flares, and rapid changes are expected in response to seismic activity. The project began as a fresh crew arrived at the International Space Station on 15 April 2005, including astronaut Roberto Vittori, who will oversee the experiment. If the theory proves to be true, then our planet's rumblings could one day be monitored from space. This is the hope and dream, but first we have to check that what has been hinted at is real. So far, evidence is still scarce
• NASA's space-shuttle fleet has not flown since Columbia broke up while re-entering the Earth's atmosphere on 1 February 2003, killing 7 astronauts. The Columbia Accident Investigation Board (CAIB) reported later that year that NASA's management culture was as much a cause of the accident as the piece of falling foam that struck the shuttle's wing during lift-off. NASA has restructured itself since then, while working intensively on ensuring that the remaining shuttles, Discovery, Atlantis and Endeavour, are safe to fly again. After 4 of the major facilities involved in getting the shuttles ready for space were battered by hurricanes in August and September 2004, NASA now hopes that Discovery space shuttle will set off on mission STS-114 between 12 May and 3 June 2005. Samples of moss aboard the doomed space shuttle Columbia have survived to reveal an unusual growth pattern that gives clues to the plant's evolutionary history. Samples of common roof moss (Ceratodon purpureus) grown in darkened containers on the shuttle put out wispy fronds in clockwise spirals. This spiralling has never been seen in any other plant in space. The moss experiments fell 64 kilometres to Earth, and were found scattered across a 5-mile area around Bronson, Texas, by retrieval crews during February and March 2004. Most of the samples were crushed, but 11 of the 87 recovered cultures were usable. One of the dishes was linked to a temperature recorder, which shows a spike in the experiment's temperature as Columbia exploded, followed by the daily fluctuations of temperature between night and day. Before returning to Earth, the astronauts had added chemicals that stopped the moss growing, so all its growth is known to have occurred in space alone. After an experiment flown on the Columbia shuttle in 1997 found spiral growth in 2 moss samples, Sack prepared 100 Petri dishes of moss seeds sealed inside aluminium containers for the Columbia's final mission. On Earth, plants can tell which way is up and direct their growth accordingly. In microgravity, they generally grow in random directions. You wouldn't expect to find such a distinctive pattern of growth in microgravity. Common roof moss grows towards light. But in the dark, gravity takes over and the moss grows upwards, as if it were escaping from beneath a layer of soil. Sack believes that removing both light and gravity reveals a more primitive mode of growing. Perhaps spirals are a vestigial growth pattern that became masked when moss evolved to respond to gravity^ref. The moss grows by sending out thin filaments; new growth occurs only at the tip. This means that a single cell at the end of the filament must sense gravity and direct the next cell's growth. We still don't know how plants sense gravity. Biologists believe that gravity moves structures that sit between the cells. These may open or close channels that carry signalling chemicals to stimulate growth in particular areas of the plant. Different plants have evolved their response to gravity separately. A spiral is a very efficient way of spreading over a wide area, so this could have been the moss's original way of growing, ensuring that space was filled without parts of the plant crossing over each other and blocking light from filaments beneath.




The space shuttle Discovery has finally reached the launch pad from which it will blast off once more into space. Discovery was rolled out in a painstaking 11-hour process that lasted into the small hours of Thu 7 April 2005. At 1:20 am local time it was finally locked into position on the launch pad at Kennedy Space Center in Florida, after travelling the 4.2 miles from its assembly hangar. The event marks a milestone on the long road back to orbit for the shuttle fleet. The 3 remaining shuttles have been grounded since 1 February 2003, when Columbia broke apart on re-entry.  Discovery has been fitted with digital cameras on its body and main fuel tank, as well as 88 temperature and impact sensors on each wing to spot any damage during take-off or orbit. NASA's website reports that officials found a small crack in the tank's foam insulation before Discovery was rolled out, but it was deemed too minor to require repair. The shuttle is now awaiting take-off, which is scheduled to happen between 15 May and 3 June. The 12-day trip is the 114th shuttle mission and Discovery's 31st flight. It will involve 7 astronauts, who will test new shuttle-safety equipment and deliver supplies to the International Space Station^ref. NASA has been forced to postpone the launch of the space shuttle Discovery after a routine test revealed a faulty fuel sensor.  The shuttle's seven crew-members, led by commander Eileen Collins, were already strapped into their seats, with just over 2 hours until blast off, when mission control scrubbed the launch. The earliest time Discovery could launch is 1840 GMT on Saturday 16 July 2005, but that may be optimistic. Worryingly, NASA has seen problems with these sensors before, but has been unable to identify the causes. The faulty sensor is 1 of 4 that measure the amount of liquid hydrogen inside the external fuel tank. The test involved sending an electrical signal telling the sensors, which read 'wet' when immersed in fuel, to flip to 'dry' instead. But the faulty sensor continued to read 'wet'. The sensors provide backup protection for the shuttle's engines by shutting them down in the unlikely event of the hydrogen supply running low, due to a leak for example. In a hastily convened press conference a few hours after the launch was scrubbed, mission managers said they had never tested what happened to an engine if the hydrogen dried up, but that it would probably be catastrophic. If the hydrogen runs out, the engines would be fed pure liquid oxygen. The eyes of the world are watching whether the agency is able to send its astronauts into space two and a half years after Columbia broke up on re-entering the Earth's atmosphere. But the shuttle has never flown with a faulty sensor before, and they are certainly not going to start now. A hint of the fuel gauge problem was spotted back in April. To prevent a problem with ice build-up on the tank, Discovery was rolled back into its hanger to have its fuel tank swapped for one with a heater. During tests, engineers also found that 2 of the 4 hydrogen sensors were giving intermittent readings.  To try to fix the problem, some of the electronics on Discovery were swapped with those from Atlantis, another of NASA's shuttles. But further testing showed more problems, so the electronics were swapped again, this time with spares from Endeavour. The actual cause of the problem was never identified. Discovery's external tanks have now been drained of the 2 million litres of liquid oxygen and hydrogen. The investigation into the fault will start with external circuits that connect the shuttle to the fuel tank, but to carry out more tests inside the tank itself, the craft may have to be trekked the 7 kilometres back to its hanger. The current launch window runs until 31 July. If Discovery misses the deadline, it will have to wait until 9 September, when the International Space Station will again be in the right position for docking. Timing this flight has been more difficult than scheduling previous shuttle missions, because the launch must happen during the day so that ground cameras can watch for falling debris, such as the chunk of foam that caused the Columbia accident. Earlier in the day, concerns were raised after a window cover fell off the front of Discovery's cockpit and damaged some of the craft's heat resistant tiles. But the repairs were completed in about an hour. The troublesome sensors may not be so easy to fix.
The space shuttle will not fly again until at least 4 March 2006, NASA confirmed on Aug 18, 2005 : extensive engineering work needs to be done on the external fuel tank to stop insulating foam debris falling off, the agency said. Until this is done, the shuttles will stay grounded. NASA has also changed its game plan for the next shuttle launch. Atlantis was meant to be next, taking to the skies in September 2005. But now Discovery is slated to make the second test flight, months later than planned. This will ensure that Atlantis, which is better equipped to carry up segments of the growing International Space Station, is ready to jump straight into the next available flight slot. The delay on this flight puts further pressure on the station, which is relying on the shuttles to deliver its remaining modules before the shuttle fleet retires in 2010. NASA administrator Mike Griffin would not be drawn on how many more shuttle flights could be launched before that planned retirement date. They're not trying to get a specific number of flights out of the system : instead the goal is simply to complete the space station, and retire the shuttle in an orderly fashion. The shuttle fleet was originally grounded after a chunk of foam tore a hole in the wing of Columbia when it launched on 16 January 2003, causing it to break apart when it re-entered the Earth's atmosphere. The shuttles returned to flight after two years of repair. But despite NASA spending more than $200 million trying to stop the foam from falling off, a similar chunk came loose when Discovery launched on 26 July. The foam did not damage Discovery, and the crew returned safely to Earth 14 days later. But they were lucky. The delay is necessary to truly fix the foam problem : they're starting to understand the mechanism of foam loss, but more work is needed. External tanks that have already been prepared for future flights will now have their foam dissected to check how well the insulating layer is stuck. Gerstenmaier and Griffin both emphasize that it may take several weeks of engineering work before 4 March is officially confirmed as a launch date. The blow to the shuttle programme comes just a day after members of the Return to Flight task group slammed NASA's approach to making the shuttle spaceworthy again. The group oversaw the way NASA carried out the recommendations of the Columbia Accident Investigation Board (CAIB), and presented its final report on 17 August 2005.  Although the majority view of the 26-strong panel was that NASA had done its utmost to fulfil all the recommendations, 7 dissenting voices made a scathing critique of NASA's efforts in an annexe to the report. The group included a former shuttle astronaut and a former chief engineer for the International Space Station. The minority group writes that launch dates were continually pushed back, so that engineers were never sure if they had months or years to tackle the foam problem. If they had known that the return to flight would take more than two years, they may have fundamentally redesigned the tank, rather than trying to make quick fixes. "Too often we heard the lament: 'If only we'd known we were down for 2 years we would have approached this very differently'. A culture of complacency among NASA managers has also persisted, they write: "NASA's leaders and managers must break this cycle of smugness substituting for knowledge. At the end of 2.5 years and $1.5 billion or more, it is not clear what has been accomplished. However, they agree with the group's consensus that the improvements did significantly reduce the risk to the shuttle and its crew, and that the shuttle was not unsafe to fly. Discovery, which landed at Edwards Air Force Base in California on 9 August, is due make the hop back to Florida on 19 August, piggy-backing on a modified jumbo jet. The journey has been delayed by difficulties in fitting an aerodynamic tail to the shuttle, which reduces drag during the flight.
Web resources :
• NASA Shuttle return to flight
• NASA: Human Spaceflight
• NASA's Shuttle programme
• Return to flight task group
• NASA's Return to Flight page
• space tourism / private space travel :
• the $25,000 Orteig prize, which spurred Charles Lindberg's 1927 flight across the Atlantic and which some credit with boosting the commercial aviation business.
• the $10 million Ansari X prize is a cash pot set up by space enthusiasts for the first private manned rocket to carry the weight of 3 people into space twice within 2 weeks, for which more than 20 teams are registered.
• SpaceShipOne was designed by Burt Rutan and his team at Scaled Composites, a company based in Mojave, California, and is backed by Microsoft co-founder and philanthropist Paul Allen : it lifted off from the California desert on 21 June 2004, strapped to the belly of a supporting aeroplane called White Knight. Once the pair reach an altitude of around 15 kilometres, the carrier plane will release the rocket. If everything goes smoothly, SpaceShipOne will shoot up to 100 kilometres, by firing its motor for 80 seconds and then cruising to the top of its trajectory. The pilot, who has not yet been named, will feel zero gravity for 3 minutes while glimpsing the darkness of space, the glimmer of stars and the remote California coastline. After falling back through the atmosphere, the rocket will glide back down to the runway. Buoyed by a successful test flight in May to over 64 kilometres, Rutan's team have invited the public to view this launch and are predicting roads jammed with spectators. SpaceShipOne differs from today's conventional rockets, which fire directly into space like missiles. And unlike the Space Shuttle, which is powered by hydrogen and oxygen, its custom built engine burns a mix of nitrous oxide and rubber, a cocktail that provides less power but is less flammable and therefore safer. If SpaceShipOne reaches 100 kilometres, it will achieve suborbital flight, meaning that it flies out of the atmosphere and grazes space, but does not go fast enough to enter a continuous orbit around the Earth. To reach suborbit, SpaceShipOne has to hit a top speed of about 1 kilometre per second; it would have to multiply that by 8 in order to enter orbit. SpaceShipOne's price-tag of over US$20 million is thought cheap compared to government-financed manned space flight. SpaceShipOne powered into space from the California desert early on Wed Sep 29 morning, completing the first half of bid to win the coveted Ansari X prize. On that trip, a hitch in the steering controls meant that the spacecraft barely scraped over the official 100-kilometre boundary between the Earth's atmosphere and space, reaching nearly 103 kilometres. Rutan's team says that it has since repaired the fault and tweaked the engine. Reports from Wednesday's flight said that the craft had rolled unexpectedly during its ascent, but flight controllers said that it had reached its target height. On 27 Sep entrepreneur Richard Branson announced that his Virgin group, which runs Virgin Atlantic airlines, had agreed to license the SpaceShipOne technology to build a fleet of spacecraft modelled on SpaceShipOne and, with tickets priced at more than US$200,000, to send up the first passengers as early as 2007. To scoop the $10-million trophy for commercial spaceflight, the rocket must repeat the flight, again carrying a pilot and the weight of 2 passengers above 100km, within 2 weeks : the second launch was scheduled for Monday 4 October, when it peaked at over 112 kilometres - the highest of the rocket's three trips into space. It also appeared smoother than last week's qualifying flight, in which the rocket was seen to make numerous rolls. The $10-million prize money was handed over to Burt Rutan, who led the Scaled Composites engineering team responsible for the craft, at a ceremony in St Louis, Illinois, on 6 November. Since then, the Ansari Foundation has announced that an annual X Prize Cup will be awarded for feats of sub-orbital space flight.


• da Vinci Project, based in Toronto, Canada : Wild Fire rocket launched from the world's largest helium balloon over 24 kilometres employs a powerful hybrid engine that burns a mix of nitrous oxide, or laughing gas, and a solid fuel. Wild Fire has got by with around US$350,000 and many volunteer hours
Web resources :
• X Prize Special at Nature
• Scaled Composites
• 'America's Space Prize', worth $50 million, is being offered by Bigelow Aerospace of Las Vegas, Nevada, a company established in 1999 by hotel magnate Robert Bigelow to build an orbiting inflatable space hotel. Bigelow also runs the hotel chain, Budget Suites of America. The prize will be awarded to a craft that can take a crew of at least 5 people to an altitude of 400 kilometres, and complete 2 orbits of Earth. This feat will have to be repeated within 60 days. The craft must be able to dock with Bigelow's space hotel (which he hopes to launch in 2008), and be capable of staying docked in orbit for 6 months. The deadline for these flights is 10 January 2010, allowing very little time for aerospace developers to prepare their entries. Bigelow had hoped to buy Russian Soyuz craft to service his orbiting hotel. But since the crash of the Space Shuttle Columbia on 1 February last year, NASA has relied on Soyuz to deliver supplies to the International Space Station. Bigelow believes that after the space-shuttle fleet is retired, NASA will still need to use the Russian ships as space workhorses. This has upped the going price for a Soyuz, and forced Bigelow Aerospace to look for alternative transport systems. Bigelow Aerospace is also offering hefty contracts for any craft that can begin bringing customers to the space hotel. The rules of the competition do not allow government funding for the projects, and teams from outside the United States are excluded from entering. This may be a response to fears that regulations designed to stop the export of military hardware from the United States could hamper progress in commercializing civilian space flight by restricting trade. The rules of the prize also state that no more than 20% of the craft's hardware must be expendable. Many space shots still rely on huge rocket boosters that are lost during launch, and coming up with reliable alternatives will be a significant hurdle for competitors.
• A US millionaire has booked a holiday with the Russian space agency that should put him in space in October 2005. But businessman, scientist and adventurer Gregory Olsen won't just be taking in the view; he says he plans to perform some experiments during his stay on the International Space Station (ISS). Olsen had originally planned to take his trip of a lifetime in April 2005, but Russian officials postponed it last summer after an undisclosed health problem was discovered. Olsen, who is about 60 years old, resumed training at Russia's Gagarin Cosmonaut Training Centre outside Moscow in May 2005, and has now signed a contract with the Russian agency. The space traveller could join a Soyuz craft that is taking supplies to the ISS as early as October 2005 and would return after 8 days in a different craft. Sources put the price of the trip, arranged through the specialist travel agent Space Adventures, based in Arlington, Virginia, at US$20 million. If successful, Olsen will become the world's third space tourist after fellow American Dennis Tito and South African Mark Shuttleworth. But Olsen prefers another description for himself: at a press conference in 2004 he said he would rather be called a "private researcher", in recognition of the fact that he is "going to do a lot of science up there". Olsen has a doctorate in materials science and started his career as a research scientist before founding 2 successful companies making electronic imaging equipment: EPITAXX and Sensors Unlimited, both based in Princeton. One of his experiments will be to grow semiconducting crystals of the type used in his company's infrared imaging products, which include cameras used for night-vision equipment. Although Olsen was unavailable to comment in more detail on the nature of his experiments, experts speculate one may have something to do with semiconductors made of unusual materials. The most commonly used semiconductor, found in computer chips, is silicon. But not all semiconductors are as easy to work with as silicon. Some other semiconductors are not so easy to grow into crystals and the effect of gravity can be limiting. It could be that Olsen has a semiconductor with certain advantages that is very sensitive to the effects of gravity. Growing crystals of such semiconductors in space could be useful. Olsen will also take one of his company's miniaturized infrared cameras aboard. He will use it for near-infrared astronomy, and to observe crops and the effects of pollution in the atmosphere from above. Infrared astronomy is difficult from the Earth: you don't get a perfect view of the sky because the atmosphere also emits infrared. But he expresses reservations about the true value of Olsen's contribution, pointing out that there are already at least two satellites with dedicated equipment to make infrared observations. It remains unclear what Olsen's experiments will contribute to the world of scientific knowledge, but his mission should certainly add to the burgeoning industry of space tourism. In addition to orbital trips, Space Adventures is developing a programme to take passengers on suborbital flights starting in 2007.
• Big Bang : tiny fluctuations in the density of matter after the Big Bang are definitely reflected in the distribution of galaxies in our Universe, according to 2 research groups. The findings confirm theories of how the Universe grew from being almost uniformly smooth to having dense clusters of stars and galaxies. Theorists calculated in the 1960s that galaxies must have been seeded in places where matter had slightly gathered together immediately after the Big Bang, which is thought to have created the Universe several billion years ago. These fluctuations were seen as ripples in the cosmic background microwave radiation by NASA's Cosmic Background Explorer in 1992, and NASA's Wilkinson Microwave Anisotropy Probe in 2003. But this radiation, which is often described as the afterglow of the Big Bang, originated a mere 400,000 years after the event, long before galaxies formed. 2 sky surveys have now seen evidence of the fluctuations in the separations of galaxies that existed 10 billion years after the Big Bang. This establishes a firm link between primordial instabilities in the Universe and the graininess we see in the cosmos today. The Two-Degree Field Galaxy Redshift Survey (2dFGRS), based at the Anglo-Australian Telescope in New South Wales, Australia, has spent 10 years mapping the distribution of 221,000 galaxies. In a complementary effort, the Sloan Digital Sky Survey (SDSS) at the Apache Point Observatory in Sunspot, New Mexico, has observed 46,000 galaxies in the northern hemisphere over 6 years. The researchers looked at the distance between pairs of galaxies, and found that there was a slight excess of those that were separated by 500 million light years, just as predicted. Seeing the ripples from the microwave background radiation amplified into the pattern of galaxies is evidence for a connection between the 2. The surveys have also provided the most accurate measurement of the mass in the Universe, finding that just 18% of its mass is visible stuff made of atoms and stable subatomic particles. The rest is dark matter, which may consist of more exotic, undiscovered particles that are only detectable through their gravitational influence on the surroundings. The amazing thing about these results is that they are in perfect accord with predictions of our standard cosmological model. This confirms that the shape of the universe must largely be decided by dark energy, the mysterious force that is driving the Universe's expansion at a much greater rate than expected. Preliminary results in 2001 had tentatively suggested that galaxies showed a characteristic distribution, but both surveys now see it very convincingly. Having matching evidence from the two groups is vital. Fundamental questions about the Universe are too important not to have a second opinion. The teams now hope to use the surveys as a yardstick to measure how the Universe's rate of expansion has changed over time. The influence of dark energy seems to have grown significantly over the last few billion years, so working out the separation of galaxies of very different ages could help to pin down exactly how the unidentified force works
• scientists searching for waves of gravitational energy that stretch space and time will soon be seeking the public's help in analysing their data. Researchers at the Laser Interferometer Gravitational Wave Observatory (LIGO) hope to enlist up to 1 million personal computers in their search for sources of the waves, which have long been predicted but never seen. Their distributed-computing scheme, set to launch on Feb 2005, aims to be one of the largest projects of its kind ever created. The software is already in beta testing. Albert Einstein's general theory of relativity lays out the idea that gravity distorts space and time. As a test of his theory, Einstein predicted that waves of gravity would ripple through the cosmos. Some claim such waves have been spotted indirectly, from observations of how paired stars influence each other's orbits, but nobody has seen them firsthand. Since 2000, researchers at LIGO have scanned the sky for tiny shifts of space that would prove Einstein's theory. The project is being built by the California Institute of Technology and the Massachusetts Institute of Technology on 2 sites, one in Livingston, Louisiana and the other in Hanford, Washington. It uses a system of lasers and mirrors that can detect a shift in space as small as the width of an atom. LIGO's best hope for detecting gravity waves is to spot a cosmic source that sends out regular ripples of gravitational energy. A source such as a spinning star made of neutrons would set the detectors ringing like a bell. The problem is that the detectors pick up an enormous number of unwanted vibrations. It's a needle in a haystack problem: 99.99% of the data is noise.  This kind of search is not anywhere near possible with LIGO computing facilities : the data must be analysed at many frequencies, increasing the computer power needed, so the group is enlisting the public's help. Starting in Feb 2004, anyone can download a program that will automatically analyse a small chunk of the group's data on his or her personal computer. The project, known as Einstein@home, will use the computer's idle time to search particular frequencies for a 'ringing' gravity wave source. While it's at work, the programme also displays a screensaver charting the location of the search in the night sky. Einstein@home joins a growing number of distributed-computing projects. The original, SETI@home, launched in 1999 to search for signals from extraterrestrials, has attracted > 5 million users. More recent attempts to model everything from climate change to protein folding have enlisted hundreds of thousands of home computers. Einstein@home will be among the most ambitious of such projects. LIGO is generating data sets so large, and looking for a signal so small, that it will take around a million active users to make a dent. But the more the merrier: the data set is so massive that even all the computers on the planet wouldn't be enough.

Web resources : GEO-600
• Long before the first stars ignited, ghostly blobs of dark matter were forming in our Universe. Dark matter produced just after the Big Bang formed into haloes as heavy as the Earth and as wide as the Solar System. The haloes' gravity would have pulled other matter together, which eventually formed stars and galaxies. These structures, the building blocks of all we see today, started forming only 20 million years after the Big Bang. There are now > 1 quadrillion (10¹⁵) of these haloes in our Galaxy alone, enough for the Earth to pass through 1 every 10,000 years^ref. Astronomers have a good chance of detecting flashes of g rays emitted by the haloes. The evidence for the haloes depends on unproven physics. Dark matter makes up > 80% of the Universe's mass. Although invisible, dark matter betrays its presence by its gravitational pull. For example, without dark matter to hold them together, rotating galaxies would simply fly apart. A leading candidate for dark matter is a particle called the neutralino, which has never been detected, but a branch of particle physics called supersymmetry predicts its existence, as a massive partner to a known particle called the neutrino. Supersymmetry models predict the neutralino's mass and how it can be created. The neutralino is its own antiparticle, so when 2 collide they annihilate each other in a blast of g rays. g rays are constantly being emitted from the dense central regions of the halo, so astronomers should be able to find physical evidence for the ancient congregations of neutralinos. And if you can detect these halos, you can backtrack to work out the precise conditions that generated them. Neutralino collisions would be extremely rare. Nevertheless, the HESS (High Energy Stereoscopic System) telescope in Namibia could pick up the flashes of light in the atmosphere caused when the gamma rays reach Earth. As the g rays enter the Earth's atmosphere they create a shower of photons that sensitive telescopes can observe. NASA's Gamma-ray Large Area Space Telescope, scheduled for launch in 2007, should be able to detect the g rays from space. Back on Earth, the Large Hadron Collider currently under construction at CERN, the European particle-physics laboratory near Geneva, Switzerland, will hunt for supersymmetric particles such as neutralinos when it opens in 2007.

Web resources : Theoretical Physics at the University of Zurich
• the Universe consisted of a perfect liquid in its first moments, according to results from an atom-smashing experiment. Scientists at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory on Long Island, New York, have spent 5 years searching for the quark-gluon plasma that is thought to have filled our Universe in the first microseconds of its existence. Most of them are now convinced they have found it. But, strangely, it seems to be a liquid rather than the expected hot gas. Quarks are the building blocks of protons and neutrons, and gluons carry the strong force that binds them together. It is thought that these particles took some moments to condense into ordinary matter after the intense heat of the Big Bang. To recreate this soup of unbound particles, the RHIC accelerates charged gold atoms close to the speed of light before smashing them together. Previous experiments have shown that these collisions create something the size of an atomic nucleus that reaches 2 trillion °C, about 150,000 times hotter than the centre of the Sun. This stuff was last seen in the Universe 13 billion years ago. Now experiments have revealed that this hot blob is a liquid, which lives for just 10-23 seconds. The surprising thing is that the interaction between the quarks and gluons is much stronger than people expected. The strength of this binding keeps the mixture liquefied despite its incredible temperature. The researchers worked out the liquid's structure by tracking the particles that spray out as the droplet falls apart and quarks team up to form normal matter. The resulting liquid is almost 'perfect': it has a very low viscosity and is so uniform that it looks the same from any angle. This may help to explain why the deepest parts of the Universe seem similar wherever astronomers look. If the primordial liquid had been as viscous as honey, the Universe could have turned out much more lumpy. The researchers now hope to measure the heat capacity, viscosity and even the speed of sound in the quark liquid. But the RHIC has been hit by cuts in the recent US budget, forcing it to reduce its operating time from 30 to 12 weeks in 2006. Further investigations will inevitably take years to complete^ref.
• g-ray bursts are sudden flashes of radiation in the sky, and their fleeting nature has made it tricky for astronomers to work out what causes them. Although some bursts last for minutes, some are visible for just a few milliseconds. Astronomers are now fairly sure that longer g-ray busts come from the collapse of massive stars. But the shorter bursts are more mysterious, and may be generated when 2 neutron stars collide. NASA's Swift satellite, which will track the most powerful explosions in the Universe, launched successfully on Saturday 20 November 2004, at 1716 GMT. Swift is an apt name for the satellite, because it can detect these short bursts and quickly turn its X-ray sensors to soak up the afterglow, providing scientists with clues about their origin : in a few minutes, they release as much energy as our Sun releases over the whole of its 10-billion-year lifetime. They are the biggest bangs since the big one. The scientists hope that Swift will detect about 3 g-ray bursts every week. The bursts were first seen in 1969 by a satellite used to monitor the Nuclear Test Ban Treaty, but it was not until the Italian-Dutch orbiting telescope BeppoSAX analysed the X-ray afterglow of a g-ray burst in 1997 that astronomers realized the explosions were coming from distant galaxies. In fact, many of the bursts seem to date from a time when the Universe was < 1 billion years old, allowing scientists to see further back into the early history of the cosmos than ever before. Swift will study these g-ray bursts in 3 different stages. The Burst Alert Telescope will be the first to spot the tell-tale rays, locking on to the signal and swivelling the satellite into the optimum observing position in as little as 20 seconds. Just 90 seconds after the burst, an X-ray telescope studies its afterglow, allowing Swift to pinpoint the source with greater accuracy. A third telescope then looks at the source in the ultraviolet and optical part of the electromagnetic spectrum, pinning down the position of the burst with even more precision. Within 5 minutes, the satellite transmits all this information back to Earth, where it is distributed to astronomers around the world by e-mail and text message. It will also trigger more powerful ground-based robotic telescopes to watch the optical afterglow that persists for many minutes after the initial burst. The launch had been delayed several times because of a problem with the craft's communications equipment. Engineers had found faults in a receiver that is responsible for picking up signals from mission control to make the rocket self-destruct if it veers off course. They fixed the problem on 19 November. Swift is now orbiting about 600 km above the Earth. After calibrating the instruments on the 5.5 m-long craft, it should be fully operational by the end of March 2005. Intense flashes of g-rays in far-off galaxies might be produced by a bizarre kind of star, consisting of phenomenally dense material in which the particles that make up atomic nuclei have fallen apart. 2 astrophysicists have proposed that g-ray bursts, whose origins have foxed astronomers for decades, might be the signatures of elusive 'quark stars'^ref. The quark-star hypothesis might explain some puzzling observations made by the Burst and Transient Source Experiment (BATSE) on NASA's Compton Gamma-Ray Observatory, which was launched in 1991. Lazzati noticed that several of the g-ray bursts seemed to be preceded, a few seconds or minutes earlier, by much weaker pulses of g-rays^ref. Astronomers generally believe that g-ray bursts are produced by supernovae: stars that have run low on fuel and do not emit enough energy to prevent them from collapsing under their own gravity. The collapse heats up the star and generates a 'rebound', in which the star's outer layers get blown off in a massive explosion, while the inner core collapses further into a superdense object called a neutron star. These stars are made entirely of neutrons, the electrically neutral particles in atomic nuclei. They measure just a few miles across and are so dense that a teaspoonful of neutron-star matter weighs about a billion tonnes. The g-ray bursts seem to be associated with a certain type of supernovae, called type Ic, in which the parent stars have already become quite compact. The g-ray flashes are produced as the supernovae throw out jets of material that move at almost the speed of light. But although only a few have so far been spotted, not all type-Ic supernovae generate these bursts. Why should the supernovae differ? The difference could depend on whether the explosion produces a neutron star or whether this superdense core contracts even more, bursting open the neutrons themselves to create a soup of quarks, the particles from which they are made. The surface of a quark star would act as a kind of filter that stops particles called baryons escaping from the star. Baryons are the components of nuclei: protons and neutrons. The surface of a quark star is a one-way street for baryons. This 'membrane' could account for the ultrafast jets squirted out of the supernova, because it would be permeable only to non-baryon particles, such as photons and neutrinos, which move at or very close to the speed of light, and would bar the ponderous baryons that slow the jets down. Crucially the transition from a neutron star to a quark star should take a few minutes. That is precisely the kind of delay between the weak precursor flashes reported by Lazzati, which would appear as the neutron star is formed, and the main g-ray bursts, which would come slightly later as it turns into a quark star. Paczyski says that the first step in testing their idea is to establish whether there are truly two classes of type Ic supernovae: one with bursts and one without. So far, there are only 4 observations from which to judge. NASA's Swift satellite spotted an energy burst at 4:00 GMT on 9 May 2005. The event, named GRB050509b, threw out a very short blast of g-rays : 90% of the event's total energy was released in just 30 ms. The blast is thought to come from 2 neutron stars colliding in a galaxy about 3 billion light years away. All of the evidence we have so far points towards this being a neutron star merger. Astronomers think the neutron-star pair originally formed when 2 orbiting stars exploded in supernovae. The dense remnants of these stars twirled around each other in ever-decreasing circles until they eventually collided and formed a black hole. Astronomers think there are several sources of g-ray bursts in the Universe. Blasts that last more than a few seconds are thought to come from the death of supermassive stars as they collapse in a violent supernova explosion. These are quite well understood, simply because the length of the bursts makes them easier to study. But short g-ray bursts have been very mysterious. Some astronomers argue that they are generated when highly magnetic neutron stars, called magnetars, throw out plumes of material. Swift's observation goes against this theory. GRB050509b is at least 10 times farther away than the most distant magnetar eruptions that Swift would be able to spy. It is more likely to be a neutron star collision, because that is a much brighter source. From simulations of neutron-star mergers, the timescales of the predicted g-ray burst match up pretty well with these observations. Swift was carefully designed to catch short bursts of g-rays and swing around fast enough to record the aftermath of whatever caused them. Just 56 seconds after detecting this burst, Swift got into position to look for the afterglow of X-rays and visible light. It then sent out e-mail alerts to astronomers around the world, who used ground-based telescopes to look at the area. No one has spotted anything so far, but this may be because the distant glow is too faint. This isn't the first microsecond burst that Swift has seen. It spotted one back in February 2005, but couldn't swing into place to observe its source because the Sun was in the way and would have blinded its sensors. This is the first one we've been able to follow up on. Spotting similar short g-ray bursts in the future will help astronomers to work out how common twinned neutron stars are throughout the Universe, and how many black holes neutron-star collisions account for. There are only 4 pairs of neutron stars known in our Galaxy.

The explosion of a star in our cosmic neighbourhood may not sound like good news for life on Earth. But a team of US researchers says that just such a catastrophe could have showered our planet with fertilizer that helped plants to colonize the land about 440 million years ago^ref. Scientists have speculated for at least a decade that g-ray bursts could have caused some of the mass extinctions in Earth's distant past. These explosions are thought to be either the by-product of a supernova, when an old star explodes, or the result of a collision between ultradense bodies called neutron stars. They release torrents of high-energy radiation (g-rays) focused into twin 'lighthouse' beams. All the bursts seen so far have occurred in distant galaxies, but in the past billion years at least one is likely to have occurred close enough to Earth to have had some dramatic effects on our planet. A nearby burst would have destroyed much of the ozone layer that protects the Earth's surface from the Sun's harmful ultraviolet rays, so that many species would have been fried. To make matters worse, the -rays would convert nitrogen and oxygen in the atmosphere into nitrogen dioxide, a brown, toxic gas that is released today in vehicle exhaust, causing urban smog. A 'g-ray burst smog' would have cast a shadow over the planet and could even have triggered an ice age. In 2003, Adrian Melott of the University of Kansas claimed that this might have happened at the end of the Ordovician period, about 440 million years ago. The geological record shows evidence at this point of mass extinctions and global cooling^ref. Melott has now collaborated with astrophysicists and atmospheric scientists to develop a computer model of the effects that a nearby g-ray burst might have. The initial results, which they reported earlier this year, looked like an unrelenting litany of disaster^ref. Ozone depletions of about 35% globally (and much more in some spots), tripled intensity of ultraviolet light, widespread DNA damage to surface organisms, and massive formation of nitrogen oxides and consequent acid rain. It all looked very gloomy. But the researchers have now delved into another side-effect. Nitric acid produced from nitrogen oxides might indeed shower the Earth with corrosive rain, but this would subsequently enrich the land in nitrate, which is an essential nutrient for plants. Today, farmers add nitrate to their soil in fertilizers. The geological record shows that it was precisely in the late Ordovician period that plants began to spread extensively over the land, in the crucial first step of colonization by life. So if a g-ray burst did cause widespread extinctions, it may also have boosted plants' growth. There was very little life on land at the end of the Ordovician, essentially just algae : plant life began to really take hold after this period, and we think that the nitrate deposited after a -ray burst could have aided this transition. Nitrate is always a limiting factor for plant growth, and would have been much more so then, before there were nitrogen-fixing plants on land. The 3-5 years of extra nitrate that we predict could have boosted plants trying to get a foothold on land.
Astronomers have spotted a signature of neutrinos created just seconds after the Big Bang. The find supports current models of the origins of our Universe, and may provide a glimpse of its birth. The fundamental particles called neutrinos are difficult to study, because they interact so weakly with normal matter - trillions whizz straight through your body every second. But the signature of primordial neutrinos is written in the cosmic microwave background (CMB). These microwaves are the remnants of light that shone 300,000 years after the Big Bang, when light was first free to move in a straight line without being blocked by the soupy material of the early Universe. Researchers have found that the CMB is slightly uneven, reflecting the lumpy distribution of matter in the early Universe. Wayne Hu, a cosmologist from the University of Chicago, proposed that neutrinos should affect these ripples in the CMB^ref. That is what Trotta and Melchiorri have found^ref. During the Big Bang, matter became patchily distributed. This was a result of matter's graininess on a small scale: subatomic particles either exist in a space or they do not, making the distribution of matter unpredictably lumpy. As the Universe grew, its lumps expanded too, spreading matter unevenly about the cosmos. The CMB, for example, contains ripples separated by about one degree - the same size as a full Moon seen from Earth. Trotta and Melchiorri worked on the assumption that fast-moving, energetic neutrinos in the early Universe changed the local gravity enough to smooth out some of the ripples in the CMB. The neutrinos' influence would have been minute, but potentially visible. When they looked at the CMB on a scale of about a hundredth to a thousandth of a degree, they found less variation than expected. This fits with the prediction that neutrinos have a smoothing effect. The fact that we can see this in the WMAP data was a big surprise. The find could help astrophysicists peer further back in time. The earliest we can see at the moment is to 300,000 years after the Big Bang. But neutrinos would have shaped the CMB from a few seconds after the Universe's birth. Learning about neutrinos in the early Universe and their interaction with the CMB should teach researchers about the other particles of that time. Such particles might, for example, stop neutrinos from smoothing out the CMB. The observations aren't definitive yet. It's not quite strong enough to call it a detection, but it goes in the right direction : the next set of data on the CMB, expected this year, could provide a firmer answer. In the meantime, it's reassuring that the results are consistent with theoretical predictions
Using a satellite and a global network of telescopes, astronomers have glimpsed the most distant cosmic explosion ever seen. The explosion, known as a g-ray burst, probably came from a star that died when the Universe was in its infancy. The light from the burst could give researchers insight into the first stars and the ways in which the cosmos has changed over time. g-ray bursts occur, most astronomers believe, during the death throes of giant stars. When stars die, they sometimes explode violently in a process known as a supernova. During the course of the explosion, a star can eject a plume of particles at near light speeds. These particles release an enormous amount of energy in the form of superfast g rays. The g-ray bursts are so intense that they can outshine entire galaxies. This event is pointing the way to the absolute first stars that ever formed. The challenge for astronomers is that most gamma-ray bursts last only a few seconds or minutes before fading away. To help locate them quickly, NASA launched the aptly named Swift satellite, a space-based g-ray telescope that locates a burst within seconds and e-mails its coordinates to nearly 1,000 astronomers around the world. The researchers race to direct their telescopes to the point in the sky where the burst was first spotted, and study its afterglow, which can last for hours or days. The light from this latest burst, which was spotted on 4 September 2005, came from a star that exploded when the Universe was a mere 900 million years old. That's about one-fifteenth of its present age. Astronomers watched the burst fade for several days, using telescopes in Hawaii, Chile, Colorado and other locations around the world. The burst provided a rare glimpse back through space and time. The light from the burst travelled through the clouds of dust that lie between the dying star and Earth, illuminating a narrow beam of the otherwise dark Universe. A Japanese group in Hawaii has gathered data that could help to show exactly what the early Universe looked like. The burst is also important because it happened at a time when the Universe was hugely different from its present state. If we can spot an explosion this old, we might eventually be able to peer even further back in time. This event is pointing the way to the absolute first stars that ever formed, before there were galaxies at all.
Web resources :
Gamma-ray burst map
• Swift at Leicester University
• Swift at the Italian Space Agency
• NASA's Goddard Space Flight Center in Maryland
• Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts
• dark galaxies : a galaxy that is made almost entirely of dark matter has been discovered. It's the first galaxy found to have no stars at all, but it fits well with predictions made by astrophysicists about where the Universe's missing mass should be. Dark matter betrays its presence by its gravitational pull: without dark matter to hold them together, rapidly rotating galaxies would simply fly apart. Scientists estimate that dark matter must be 5 times more abundant than normal matter in our Universe. It is likely to be made of relatively large subatomic particles that rarely interact with their surroundings, although these particles have never been identified. In fact, > 90% of our particular Galaxy's mass seems to be dark matter. The normal matter was pulled into stars, planets and dust clouds, but this doesn't seem to have happened in the dark galaxy. What's bizarre is that the galaxy hasn't converted any gas into stars at all. The dark galaxy, named VIRGOHI21, is in the Virgo cluster, a large group of galaxies about 50 million light years away. It has roughly 10% of the mass of our own Galaxy, the Milky Way, but it's not uncommonly small^ref. The team's first clue came from the behaviour of the neutral hydrogen atoms that shroud this dark region of space. The researchers detected the characteristic radio-frequency signature of these atoms using the Lovell Telescope at the Jodrell Bank Observatory near Manchester, UK. They found that the hydrogen was swirling in exactly the same way as it would swirl around a normal, brightly lit galaxy. At first, they assumed that they were simply looking at a dim, dwarf galaxy. But by watching how the hydrogen moved, the researchers were able to calculate that the mass of the galaxy is relatively large. However, normal matter packed that close should have ignited some stars. If it were an ordinary galaxy, then it should be quite bright and would be visible with a good amateur telescope. He and his colleagues used the powerful Isaac Newton Telescope on La Palma in Spain's Canary Islands, to look for any scraps of visible light from the area; they found nothing. The most likely explanation is that the galaxy is made of dark matter. The inability to find dark galaxies has been a thorn in the side of theories about how dark matter shapes our Universe, which predict that there should be even more dark galaxies than visible ones. Scientists have also speculated that haloes of dark matter might be the gravitational seeds of galaxies, attracting enough normal matter to form stars. The team now plans to use radio telescopes to hunt for more dark galaxies
• magnetars are extremely dense, small stars with magnetic fields at least a thousand trillion times stronger than the Earth's. They are a type of neutron star, the compact remnant of a collapsed sun.
• a cataclysmic 'starquake' is thought to have caused a flare of radiation that ripped past the Earth on 27 December 2004, battering instruments on satellites and lighting up our atmosphere. This is the biggest blast of g and X-rays they have ever observed in our corner of the Universe. They believe the flare came from a bizarre object just 20 km wide on the other side of the Galaxy that released more energy in 0.1 s second than the Sun emits in 100,000 years. Data from satellites and ground-based telescopes have pinpointed the origin of the burst as SGR 1806-20, a 'magnetar' around 50,000 light-years away in the constellation of Sagittarius. The flare may have been caused by a quake on the surface of SGR 1806-20. The quake would have disturbed the star's magnetic field, creating an explosion that was the brightest ever detected beyond our Solar System. It is possible that similar flares have been misinterpreted in the past. Analogous g ray bursts have been detected, but they were assumed to come from very distant objects beyond our galaxy. Fortunately for life on Earth, the nearest known magnetar is about 13,000 light years away - too far for any future burst to damage the planet. The radiation burst from a closer explosion could, for example, wipe out the ozone layer
• a source of ultra-high-energy cosmic rays has been identified for the first time. The extremely energetic particles, racing at almost the speed of light, have been traced back to a pair of colliding galaxy clusters. Cosmic rays are fast-moving particles that constantly bombard the Earth. Some come from the Sun, whereas higher-energy rays are accelerated around the remnants of supernovae. But ultra-high-energy cosmic rays are at least a thousand times more energetic still, and extremely rare. Only one particle is expected to hit each km² of Earth every century. Physicists already know that these particles are almost certainly protons whose energies are measured in exaelectronvolts (10¹⁸ eV) - the amount of energy that an electron acquires when it is accelerated by a billion billion volts. Each proton has a kinetic energy similar to that of a flying golfball, and travels at just one part in 10²² slower than the speed of light. 5 of these particles all came to Earth from a pair of galactic clusters that are crashing together roughly 450 million light years away. Only about 100 of these ultra-high-energy cosmic rays have been detected on Earth in the past decade, and until now all of them seemed to come from different parts of the sky. They travel so fast that magnetic fields in space can barely alter their paths. This means that the particles travel in a virtually straight line to Earth, allowing to plot their paths and work out where they came from. Data came from 2 separate detectors. The High Resolution Fly's Eye fluorescence detector in Dugway, Utah, searches Earth's atmosphere for streaks of light generated when the particles hit. The impacts make the atmosphere fluoresce in a line, and that line points directly at the source. The impacts also start a cascade of secondary reactions in the air, generating millions more particles that shower Earth's surface. The Akeno Giant Air Shower Array (AGASA) in Asao, Japan, has particle detectors covering an area of 100 km². If all the detectors fire at the same time, this indicates a massive event that could only have been triggered by the arrival of an ultra-high-energy cosmic ray. The 5 events that Farrar tracked were spotted between 1993 and 2003. The difference in their arrival time is due to the very slightly different paths they took to reach Earth even the tiniest deviation from a straight line can make a decade's difference over such huge distances. The paths all point to the merging galaxy clusters, a conclusion supported by observations from the Sloan Digital Sky Survey (SDSS), run from the Apache Point Observatory in New Mexico, which show that there is a clear line of sight between Earth and the clusters. The clusters are extremely rich in stars and have powerful magnetic fields that become warped when they collide. It's possible that the turbulent magnetic fields accelerate charged particles such as protons in tight spirals before flinging them towards us. Some physicists have speculated that such energetic particles could only come from the decay of exotic, heavy subatomic particles formed immediately after the Big Bang. But seeing 5 high-energy rays from the same point rules that out, because the chance of finding that many exotic decays along the same line of sight is minuscule
• telescopes :
• ground-based telescopes are usually plagued by the Earth's atmosphere, which bends starlight back and forth as the beams pass through pockets of air with different densities. The effect is similar to the apparent shimmering of a desert, caused by looking through hot air rising from the scorched sand. The calm air above part of the Antarctic makes it the best place on Earth for astronomy. Dome C is the best ground-based site to develop a new astronomical observatory. Even at high-altitude sites elsewhere on Earth, stars seem to jitter in the sky, moving by about 140 millionths of a degree. But over Dome C, the jitter was as low as 19 millionths of a degree, by far the best value ever reported. in order to compare to an optical or infrared telescope built at Dome C, a telescope built at one of the next best sites around the world would have to be two or three times as large. A Dome C telescope could even work on projects that would otherwise require a space mission, they add, and could potentially assist in the hunt for Earth-like planets beyond our solar system. Antarctica was already known to be an attractive location for a telescope because it is so far away from the interference of urban light, heat and smog, and it is also one of the least cloudy places on Earth. Telescopes have been built at increasingly high altitude to reduce the distance the starlight must travel through our turbulent atmosphere. Some telescopes are fitted with hundreds of tiny motors, which move the telescope's mirror to compensate for the jittering. But 'adaptive optics' can only reduce, and not eliminate the effect. Any proposal would require a rigorous impact assessment as in Antarctica we have the most stringent environmental protocols in the world. Anyway there is no wildlife in that part of the Antarctica to disturb, whereas a telescope built in a remote part of Chile, for example, would have a much greater effect on the environment^ref.

space telescopes : Hubble avoids the jittering problem altogether, because it orbits above our atmosphere. Hubble has provided astronomers with some of our best views of the cosmos, spotting planets around distant stars and revealing what the Universe looked like in its earliest years. Hubble has been photographing the Universe for 14 years and was designed to be serviced regularly. But as its batteries run down and its stabilizing gyroscopes fail, Hubble will lose the ability to focus on a fixed point. NASA expects that this may happen sometime in 2007. 4 successful overhauls between 1993 and 2002 were due to be followed by a fifth and final upgrade to the telescope's batteries and gyroscopes, before the Columbia shuttle crash on 1 February 2003 grounded NASA's remaining shuttles. The ailing Hubble Space Telescope should be rescued by humans rather than robots as early as possible after the shuttle is deemed safe to fly. Without prompt action, Hubble could degrade to the point where repair would be impossible, and may even be unsafe to take out of orbit. NASA expects it to take > 3 years to develop a robot mission, and the committee says that this might be too late to save Hubble anyway. It also argues that the risks that a servicing mission pose to a shuttle crew are little different from those involved in building the International Space Station. NASA plans 28 shuttle flights to complete the station by 2010. Space consultants Aerospace Corporation delivered a similar assessment report, commissioned by the space agency, earlier this week. It too found that a robotic repair mission would be more expensive and riskier than NASA had originally anticipated. The panel believes that astronauts would be better than a robot at dealing with unforeseen repairs, something that has been necessary on three of the four previous servicing missions. With proper attention, Hubble could continue operating well into the next decade. US Officials revealed on Friday 21 Jan 2005 that NASA's budget for 2006 contains no cash to save the ageing telescope. Instead, it earmarks funds to decommission the instrument. President George W. Bush will present the budget proposal on 7 February, and the US Congress will then consider it. The telescope could yet win a reprieve. Congress could insist on boosting NASA's budget to include the costs of a servicing mission, as they did in 2004. And NASA has enough flexibility in how it spends its US$16.2 billion budget for 2005 to devote some resources to a rescue mission. NASA spokeswoman Dolores Beasley said that the agency would make no official comment on the forthcoming budget until 7 February. Astronomers insist that a repaired Hubble could deliver valuable science well into the next decade. Although ground-based telescopes can now see further and more clearly into the Universe than ever before, many astronomers still rely on Hubble to glimpse the most distant stars. Hubble has been orbiting the Earth since April 1990, photographing distant stars formed in the earliest stages of the Universe. But 2 of the 6 gyroscopes that stabilize the telescope no longer work, and as more fail Hubble will lose its ability to focus on a fixed point. Its batteries also need replacing before they run down, which is expected to happen in 2007 or 2008. The debate on how to repair Hubble has lasted for > 1 year. On 8 December 2004, an influential committee of the US National Academies' National Research Council recommended that NASA launch a manned rescue mission to service Hubble as soon as possible. But outgoing NASA administrator Sean O'Keefe has always rejected a manned mission as too risky, favouring a robotic saviour instead. Each option would cost at least US$1 billion. Now it seems that Hubble's last visitor may be charged with guiding it into an orbit that brings the telescope crashing safely into the Pacific Ocean. The budget leaks, widely reported in the US media, may be an attempt by Hubble supporters in the government or NASA to put the debate firmly back in the public arena. The fuss could put pressure on politicians to save the popular mission. It's thought that President Bush wants to invest in manned space missions instead of repairing the Hubble. Hubble has been serviced by the space shuttle 4 times in the past 15 years. A fifth mission was scrapped after the shuttle Columbia crashed on 1 February 2003, putting NASA's fleet out of commission while it made safety checks. The Discovery shuttle is expected to fly in May 2005. The shuttles will devote much of their time to completing the International Space Station, but a lot of people feel that's a white elephant. The case for spending billions of dollars refurbishing the shuttle would be much stronger if it was going to be used to save Hubble. The Hubble Space Telescope will be scrapped, according to NASA officials who presented the agency's budget for 2006 on 7 February 2005. No money has been set aside for a vital servicing mission, which would replace the telescope's ageing batteries and gyros, but would cost hundreds of millions of dollars. Instead, NASA has given Hubble just US$93 million, with the lion's share earmarked for nudging it out of orbit. NASA engineers are expected to deliver a report in March on how to retrieve the telescope safely. NASA administrator Sean O'Keefe says that the budget reflects President George W. Bush's commitment to manned space exploration missions, which has shifted the agency's focus towards the Moon and Mars. Hubble's supporters are dismayed by the decision. Barbara Mikulski, Democrat senator for Maryland, will fight in the Senate this year to fund a servicing mission to Hubble by 2008. But time is running out for the telescope's supporters. Congress will have to make a decision about Hubble very soon, probably no later than the end of March. A committee of the US National Academies' National Research Council recommended on 8 December 2004 that NASA launch a manned rescue mission to Hubble as soon as possible, ruling out a robotic mission as unworkable. But outgoing NASA administrator Sean O'Keefe has always argued that the tighter safety regulations proposed by the Columbia Accident Investigation Board make a manned servicing mission too risky. NASA software engineers have developed a strategy to keep Hubble focused on the stars for a little longer. This means that 2 of the telescope's 4 remaining gyros, which keep it pointing in the right direction, could be kept as a spares. This might buy Hubble an extra year of life. NASA's purse fared better than those of many other government departments, including energy and basic defence research. The agency's $16.5-billion request was 2.4% higher than last year's final allowance. The largest portion of funding ($4.5 billion) goes to the shuttle, which is expected to return to flight in May or June 2005. The International Space Station, expected to be completed in 2010, will receive $1.9 billion. NASA hopes that the station can be used for more research on the health effects of arduous manned missions. The budget also grants $372 million (a 19% increase) to the James Webb Space Telescope, which is seen by many as Hubble's successor and is expected to launch in August 2011. But the Jupiter Icy Moons Orbiter, a craft that would have relied on nuclear propulsion, has effectively been cancelled. NASA officials now say that the orbiter is just too ambitious, and will not be realized by the proposed 2015 launch date. O'Keefe has been plagued by the quandary over Hubble, and formally resigned from NASA on 13 December 2004. He now expects to leave the agency within days; he will begin his job as chancellor of Louisiana State University, Baton Rouge, on 21 February. April 2005 marks 15 years since the Hubble Space Telescope, hailed by some commentators as the most successful astronomy mission ever, was placed in orbit. Since 25 April 1990, it has snapped 750,000 images, sending 120 gigabytes of data back to Earth each week. But now the end may well be nigh for the ailing telescope. Perhaps Hubble's most impressive achievement is to have peered into the farthest recesses of the Universe, allowing cosmologists the chance to witness the first stars in the act of formation. Images called the Hubble Ultra Deep Fields , taken using lengthy exposures of around 1 million seconds, capture light from so far away - which has travelled for so long to reach us - that the pictures show astronomers what was happening almost as far back as the Big Bang. In recent years, Hubble has also taken ultraviolet images of Saturn's striking aurorae , captured high-speed galactic collisions , and provided hundreds of posters for physics students' bedroom walls. Hubble takes images right across the visible spectrum and into the infrared and ultraviolet wavelengths on either side. The final images presented to the public are likely to have been run through a statistical computer package to iron out background blur or unwanted features, and to sharpen up the subject of the image. The photographs will also probably have had their colour, contrast or brightness tweaked. And for infrared or ultraviolet images, the frequencies of the final image will have been shifted to make them visible. Much of this processing, however, is exactly what astronomers would do when preparing the images for their own use, so they are more than just pretty pictures. It looked to be all over for Hubble when NASA announced its 2006 budget in February 2005. The plan allocated just $93 million to the telescope, most of which was earmarked for getting it safely out of orbit, leaving little for crucial maintenance. Without such repairs, Hubble's batteries are due to run out in 2007 or 2008. The hiatus in shuttle flights after the Columbia disaster has also prevented crews from getting into space to fix the telescope. But Hubble may have been handed a lifeline in the shape of new NASA chief Michael Griffin. He has pledged to revisit the idea of a manned servicing mission, which would cost an estimated $1 billion. He has ruled out the idea of a robotic mission as impractical. If the decision is taken to rescue it, astronauts will travel to Hubble to replace its battery pack, which pumps out the equivalent of 20 car batteries, and its ageing stabilizing gyros. Without such a mission, a robot is likely to be sent up to pull the schoolbus-sized telescope out of orbit and guide it to a safe splashdown in the ocean. Hubble is part of NASA's Great Observatories Program, a four-strong team of space telescopes designed to span a wide range of different wavelengths. Two other space observatories will likely out-live Hubble: the Spitzer Space Telescope, which takes infrared images, and the Chandra X-ray Observatory. The final member, the Compton Gamma-Ray Observatory, was decommissioned in 2000 after 9 years in orbit. Hubble's successor will be the James Webb Space Telescope - also designed to peer into the early Universe. Scheduled for launch in August 2011, this instrument will sit 1.5 million km from Earth, and look at light in the infrared. From its vantage point in space, Hubble has given astronomers views of the Universe they could not have got from under Earth's blanket of magnetic fields and radiation. Launched at a cost of $1.5 billion, it has now had three servicing missions, only one of which - a trip to fix a focusing defect in one of its mirrors - was unplanned. The telescope was initially seen as having a potential working lifetime of 20 years. But given its prolific output, each image has averaged a cost of just a few dollars. Even if the telescope's champions fail in their campaign to save it, Hubble can retire with the satisfaction of a job well done^ref.
• a few precious spots on the Moon may be bathed in permanent sunlight, according to planetary scientists. These bright, temperate areas might make ideal sites for a lunar base. Researchers have long suspected that mountains and crater rims at the Moon's poles might bask in constant sunshine. But without a detailed analysis of the lunar landscape, this has been a tough theory to test. A team led by Ben Bussey of the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, analysed pictures taken by the spacecraft Clementine, which circled the Moon in 1994. The researchers overlaid a series of images of the Moon's north pole taken over a lunar day - which lasts about 28 Earth days - and searched for regions that are constantly illuminated. A handful of spots on the rim of the Peary crater were lit for the entire lunar day and may be sun-baked all year ro