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Satellite

Experts urge US to share data on satellite orbits

David Shiga
New Scientist
Wed, 29 Apr 2009 18:25 UTC
Image
© ESA
The US Air Force tracks more than 19,000 pieces of debris larger than 10 centimetres long. Here, satellite sizes have been exaggerated for visibility in this artist's impression of the environment in low-Earth orbit.
The US government's reluctance thus far to release precise data about the satellites it is tracking is hampering efforts to prevent collisions in space, a satellite industry executive told a congressional committee on Tuesday.

The US tracks and predicts the orbits of the world's satellites and thousands of bits of space junk as small as 10 centimetres across, using radar and telescopes on the ground. But it closely guards its most precise data, and routinely releases only lower-precision data to satellite companies and other countries.

That makes it difficult for satellite operators to predict a collision with another satellite or piece of space junk, said Richard DalBello of satellite operator Intelsat General in testimony to a congressional hearing on Tuesday about space debris and safety.

To help avoid accidents like the one in February in which a Russian communications satellite collided with an American one, some commercial operators are pooling information on the positions and orbits of their satellites, based on their own tracking data.
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Saturn

Salt in Enceladus geyser points to liquid ocean


New Scientist
Wed, 29 Apr 2009 18:19 UTC
The ice plumes that bloom above Saturn's icy moon Enceladus are almost certainly rooted in a subsurface sea of liquid water.

The Cassini spacecraft flew through a plume on 9 October 2008 and measured the molecular weight of chemicals in the ice. Frank Postberg of the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, and colleagues, found traces of sodium in the form of salt and sodium bicarbonate. The chemicals would have originated in the rocky core of Enceladus, so to reach a plume they must have leached from the core via liquid water. Observations from Earth in 2007 spotted no sign of sodium, casting doubt on such a subsurface sea.

Although the salt could have been leached out by an ancient ocean which since froze solid, that freezing process would concentrate most of the salt very far from the surface of the moon's ice, says Julie Castillo of NASA's Jet Propulsion Laboratory in Pasadena, California. "It is easier to imagine that the salts are present in a liquid ocean below the surface," she says. "That's why this detection, if confirmed, is very important."
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Blackbox

Antimatter mysteries 3: Does antimatter fall up?

Amanda Gefter
New Scientist
Wed, 29 Apr 2009 18:17 UTC
Image
© Martin Lee / Rex Features
Gravity works the same way on all normal matter, but might antimatter respond differently?
Gravity, we think, works the same way on all matter. But what about antimatter?

AEGIS, a CERN experiment that has just been given the go-ahead, is designed to find out. Gravity is a relatively weak force, so the experiment will use uncharged particles to prevent electromagnetic forces drowning out gravitational effects. It will first build highly unstable pairings of electrons and positrons, known as positronium, then excite them with lasers to prevent them annihilating too quickly. Clouds of antiprotons will rip these pairs apart, stealing their positrons to create neutral antihydrogen atoms.

Pulses of these anti-atoms shot horizontally through two grids of slits will create a fine pattern of impact and shadow on a detector screen. By measuring how the position of this pattern is displaced, the strength - and direction - of the gravitational force on antimatter can be measured.

It's a clever idea, but the devil is in the detail, says AEGIS spokesman Michael Doser. "No one has ever made controlled positronium like this, nobody has ever made a positronium excited state with lasers in an environment like this and nobody has ever made an antihydrogen pulse like this."
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Telescope

Vanishing matter points to back hole in Milky Way

David Shiga
New Scientist
Wed, 29 Apr 2009 17:36 UTC
Image
© Q D Wang et al / UMass Amherst / CXC / NASA
The centre of the Milky Way, as seen from NASA's Chandra X-ray Observatory. New evidence strongly suggests that there is a black hole lurking in there.
Matter and energy are vanishing without a trace at the centre of the Milky Way, providing the best evidence so far that a black hole is lurking there.

Falling into a black hole is aone-way trip - once matter or light crosses a threshold called the event horizon, it can never escape. While astronomers have identified many dark, dense objects they strongly suspect are black holes, it is difficult to prove that they possess event horizons, the defining feature of such objects. Among the proposed alternatives are dense balls of exotic matter called boson stars, which don't have event horizons.

Now Avery Broderick of the Canadian Institute of Theoretical Astrophysics and his colleagues have analysed previous infrared and radio observations of the galactic centre and put forward the strongest evidence yet that an object at our galaxy's centre does indeed have an event horizon.

The team reasoned that if the object were not a black hole, it should glow in the infrared. This is because the kinetic energy of matter hitting the object would be converted into heat. Given the rate that matter appears to be falling onto the central object, it should have a temperature of at least a few hundred Kelvin, they calculate. The resulting infrared glow would be 250 times as bright as the actual glow coming from the region containing the massive object and its disc of matter, when previously measured during quieter moments when the disc is not flaring up.
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Meteor

Asteroid Threat: Call the Lawyers

Jeremy Hsu
Space.com
Wed, 29 Apr 2009 07:59 UTC
Asteroid Impact
© Don Davis
Artist's rendition of an Asteroid Impact
Asteroids that might threaten Earth could pose a challenge beyond the obvious, if nations can't get their act together and figure out a unified plan of action.

There are currently no known space rocks on a collision course with Earth, but with ample evidence for past impacts, researchers say it's only a matter of time before one is found to be heading our way.

A swarm of political and legal issues bedevil any national or international response, whether it's responsibility for collateral damage from deflected asteroids or the possible outcry if one country decides to unilaterally nuke the space threat.
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Star

Missing planets suggest stars 'eat' their young

Rachel Courtland
New Scientist
Tue, 28 Apr 2009 09:54 UTC
Planets orbiting near their stars
© Mark Garlick/HELAS
Planets orbiting near their stars may not last for very long
Exoplanets that venture near their host stars are doomed to premature deaths - even before they get close enough to be ripped apart by the stars' gravity, two new studies suggest.

A star's gravity can put a nearby planet on a 'fast track' to spiralling into the star and may also cause the planet to lose much of its atmosphere, the studies say. The research may help explain why few exoplanets have been found right next to their host stars.

More than 300 exoplanets have been catalogued to date. Many are situated close to their host stars, where it is thought to be too hot for gas and dust to collapse into planets in the first place. That implies that the planets came from farther away and migrated inwards.
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Telescope

NASA satellite spots oldest, most distant cosmic explosion

Sharon Gaudin
Computerworld
Tue, 28 Apr 2009 00:31 UTC
Using a NASA satellite, astronomers have gotten a glimpse of the oldest object in the universe that humans have ever seen. NASA announced today that its Swift satellite and a global team of astronomers have detected a 10-second, gamma ray burst (see video) from a star that died when the universe was just a baby. The burst, called the "most distant cosmic explosion ever seen," happened when the universe was only 630 million years old.

Scientists estimate that the universe is now some 13.73 billion years old.
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Blackbox

Antimatter mysteries 1: Where is all the antimatter?

Amanda Gefter
New Scientist
Mon, 27 Apr 2009 16:00 UTC
Image
© NASA / N Benitez (JHU) / T Broadhurst (Racah Institute of Physics/The Hebrew University) / H Ford (JHU) / M Clampin (STScI) / G Hartig (STScI) / G Illingworth (UCO/Lick Observatory) / the ACS Science Team and ESA
Galaxies, like Abell 1689, should not exist at all according to the standard model of physics.
If you were to list the imperfections of the standard model - physicists' remarkably successful description of matter and its interactions - pretty high up would have to be its prediction that we don't exist.

According to the theory, matter and antimatter were created in equal amounts at the big bang. By rights, they should have annihilated each other totally in the first second or so of the universe's existence. The cosmos should be full of light and little else.

And yet here we are. So too are planets, stars and galaxies; all, as far as we can see, made exclusively out of matter. Reality 1, theory 0.

There are two plausible solutions to this existential mystery. First, there might be some subtle difference in the physics of matter and antimatter that left the early universe with a surplus of matter. While theory predicts that the antimatter world is a perfect reflection of our own, experiments have already found suspicious scratches in the mirror. In 1998, CERN experiments showed that one particular exotic particle, the kaon, turned into its antiparticle slightly more often than the reverse happened, creating a tiny imbalance between the two.
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Blackbox

Antimatter mysteries 2: How do you make antimatter?

Amanda Gefter
New Scientist
Tue, 28 Apr 2009 16:04 UTC
Image
© Laurent Guiraud / CERN
The ATHENA experiment at CERN. Antiprotons enter from the AD (left) and are captured in a trap inside the superconducting magnet (left). The positron accumulator (right) provides the positrons for producing antihydrogen.
If we really wish to fathom the mysteries of antimatter, we must first get to grips with the stuff itself. Easier said than done. How on earth do you pin down a substance that vanishes the moment it touches anything?

Two CERN experiments, ATRAP and ALPHA, are grappling with that question. Their aim is to make antihydrogen - the simplest anti-atom possible, just an antiproton and a positron bound together - in sufficient quantity and for long enough to compare the spectrum of light it emits with that of regular hydrogen. Even the slightest difference between the two would shake up the standard model.

The experiments require a near-perfect vacuum, as encountering a mere atom of air would spell the end for any antiparticle, and there must be some way of trapping the antiparticles: not in a conventional container, but using electric and magnetic fields.
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Info

Self-healing concrete for safer, more durable infrastructure

Nicole Casal Moore
University of Michigan
Wed, 22 Apr 2009 01:24 UTC
Image
A concrete material developed at the University of Michigan can heal itself when it cracks. No human intervention is necessary - just water and carbon dioxide.

A handful of drizzly days would be enough to mend a damaged bridge made of the new substance. Self-healing is possible because the material is designed to bend and crack in narrow hairlines rather than break and split in wide gaps, as traditional concrete behaves.

"It's like if you get a small cut on your hand, your body can heal itself. But if you have a large wound, your body needs help. You might need stitches. We've created a material with such tiny crack widths that it takes care of the healing by itself. Even if you overload it, the cracks stay small," said Victor Li, the E. Benjamin Wylie Collegiate Professor of Civil Engineering and a professor of Materials Science and Engineering.
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