Astronomical News

There may be yet more stuff out at the edge of the solar system (and why it won't be a invisible death star).

Solar system planetoids could be really far out
16:43 20 January 2005 news service
Maggie McKee

Large planetoids may have formed hundreds of times farther from the Sun than previously thought, new calculations reveal. The work suggests a vast population of undetected icy bodies - like the recently discovered Sedna - may skirt the fringes of the solar system.

All of the objects in the solar system are thought to have condensed from a disc of dust and gas, starting about 4.5 billion years ago. But the process was far from orderly.

Observations of comets suggest some objects that formed in the disc - probably around the orbit of Saturn - were flung outwards within 100 million years. These scattered bodies are currently believed to make up a shell called the Oort Cloud that surrounds the solar system like a bubble.

The astronomers who discovered the large object Sedna in November 2003 think it may be one of these scattered objects. The planetoid is nearly the size of Pluto and about three times as far away.

But now, Alan Stern, director of space studies at the Southwest Research Institute in Boulder, Colorado, US, says Sedna may have formed at its current distance - or perhaps even farther out.

Cut-off point
This suggestion is based on computer simulations that assume the solar system's original gas and dust disc extended beyond the Kuiper Belt, a ring of icy objects beyond Neptune. This belt, first discovered in 1992, seems to cut off abruptly at 50 astronomical units (1 AU being the distance between the Sun and Earth). The cut-off delineates an apparent "edge" to the main portion of the solar system.

But when Stern tested models in which the disc extends out to 500 AU, those containing relatively high densities of material produced planetoids like Sedna in just 100 million years.

"The implication is that our solar system's planet-forming disc was really large," Stern says. "The outer edge of the Kuiper Belt may actually be the inner edge of a gap in the disc." Such a gap may have been carved out early in the solar system's history by a passing star or a Mars-sized planet being ejected into space.

Compact disc
He adds that dusty discs have been seen around other stars and tend to be big, with diameters of up to 3000 AU. "It's rare to find a compact disc like the Kuiper Belt," he told New Scientist. "Instead of trying to explain why ours is different, I thought: what if it isn't?"

Stern says Sedna was probably born in a circular orbit, possibly as far away as 500 AU. But he agrees with other astronomers who say that a passing star or unseen planet must have knocked it into its current, elongated trajectory, which stretches from about 75 to 900 AU.

The simulations suggest many hundreds of objects like Sedna may have formed at those distances. Stern admits that finding the extremely faint objects will be incredibly hard, but says his theory would be bolstered if deep surveys turned up far-distant objects in circular orbits.

But Renu Malhotra, an astronomer at the University of Arizona in Tucson, US, has some reservations about the work. She says dust thins out toward the outer edges of a disc, so building distant objects as big as Sedna within the age of the solar system "is pretty hard even in very large discs".

And quick timing is crucial. If a passing star did cause Sedna's extreme orbit, that suggests the planetoid must have formed in solar system's first 100 million years - the time it took to assemble the Oort Cloud. If the star passed by after that time, it would have disturbed and dissipated the cloud.

She also questions Stern's suggestion that other planetoids would lie in circular orbits. Any passing star that disturbed Sedna's orbit would probably also affect its siblings, she told New Scientist. But she says the discovery of the Kuiper Belt's edge at 50 AU in recent years has puzzled theorists and says Stern's paper "suggests we should keep our minds open to the possibility that what we're seeing is indeed a gap".

Journal reference: Astronomical Journal (vol 129, p 526)

New Scientist
U.S. to Cut Funds to Fix Hubble Telescope-Source


U.S. to Cut Funds to Fix Hubble Telescope-Source
Sun Jan 23, 2005 11:28 AM ET

By Caren Bohan and Deborah Zabarenko

WASHINGTON (Reuters) - The Bush administration plans to propose cuts in funds to fix the aging Hubble Space Telescope, a U.S. official said on Saturday, as the head of the telescope project said he hoped Congress would approve money for repairs.

The 14-year-old orbiting observatory has produced path-breaking science and created a popular appetite for its spectacular images of the cosmos. It is due for a servicing mission to replace its batteries and the gyroscopes that keep it steady, and to upgrade some of its equipment.

The repair mission has been on hold since the Feb. 1, 2003, disintegration of shuttle Columbia. Debate in the astronautical community has raged over whether to send robots or astronauts to fix the telescope, or whether to fix it at all.

Reports on the Web site and in The Washington Post said the Bush administration plans to scrap any Hubble repair mission and eliminate those funds from the proposed budget for fiscal 2006. A U.S. official confirmed those reports.

Bush will release his fiscal 2006 budget proposal on Feb. 7.

Speaking on condition of anonymity, the U.S. official told Reuters the estimated cost of a robotic repair was $2 billion and one feasibility study gave it an 80 percent chance of failure.

"Hubble is in year 14 of a planned 15-year mission," the official said. "Trying to send a robotic mission to extend that time period would be a $2 billion gamble with taxpayer dollars where the odds are 80-20 that it would fail."

The official also noted that a National Academy of Sciences panel concluded a shuttle repair mission would have a greater chance of success, but said outgoing NASA Administrator Sean O'Keefe has ruled this out as too risky for astronauts.


Steve Beckwith, head of the Space Telescope Science Institute that manages Hubble, said he was surprised by the reports, and questioned the relative risk of sending astronauts to the orbiting telescope.

Beckwith said the National Academy of Sciences report found an astronaut mission to fix Hubble would be no riskier than a shuttle mission to the International Space Station.

"I understand that they plan to fly between 25 and 30 flights to complete the space station ... so I would hope that if NASA plans to continue flying the space shuttle, that one of those flights can go and service Hubble, because that will have a very high probability of mission success," Beckwith said.

He discounted the unnamed U.S. official's assessment that the telescope is nearing the end of its useful life.

"Hubble could easily live well beyond 20 years, and furthermore, the National Academy committee stated that the future discoveries from Hubble over the next five years are every bit as bright as the discoveries we've seen in the past," Beckwith said.

"I'm hoping that our lawmakers will see the value of Hubble and make it a priority in NASA's budget," he said.

Sen. Barbara Mikulski, a Maryland Democrat who has championed Hubble and other NASA space science projects, said in a statement on Friday: "It is essential that we have a safe and reliable servicing mission to Hubble ... I led the fight to add $300 million to NASA's budget last year for a Hubble servicing mission, and I plan to lead the fight again this year."

NASA's O'Keefe announced plans to ax the Hubble repair mission a year ago, just days after President Bush unveiled a plan to send humans back to the Moon and eventually to Mars. Public outcry and congressional pressure prompted a reconsideration.

Blazing speed: The fastest stuff in the universe


Blazing speed: The fastest stuff in the universe

By Robert Roy Britt
SPACE.comexternal link
Tuesday, January 18, 2005 Posted: 11:05 AM EST (1605 GMT)

( -- If you're light, it's fairly easy to travel at your own speed -- that is to say 186,282 miles per second or 299,800 kilometers per second.

But if you are matter, then it's another matter altogether.

Nothing we know of zips along more quickly than light. Einstein, nearly 100 years ago, said it's not possible. For us, the speed limit makes strange sense: Go faster than light, and you could return before you've left, become your own grandpa, or other perform other leaps of cosmic logic.

Fast forward a century. Astronomers are now measuring stuff -- material, matter, things -- that moves at so close to the speed of light you might think it'd make Einstein a bit nervous. His theory of relativity appears not to be endangered by the blazing speeds, though.

Among thee speed demons of the universe are Jupiter-sized blobs of hot gas embedded in streams of material ejected from hyperactive galaxies known as blazars. Last week at a meeting here of the American Astronomical Society, scientists announced they had measured blobs in blazar jets screaming through space at 99.9 percent of light-speed.

"This tells us that the physical processes at the cores of these galaxies ... are extremely energetic and are capable of propelling matter very close to the absolute cosmic speed limit," said Glenn Piner of Whittier College in Whittier, California.

Ponder the power of the fast moving superheated gas, known as plasma:

"To accelerate a bowling ball to the speed newly measured in these blazars would require all the energy produced in the world for an entire week," Piner said. "And the blobs of plasma in these jets are at least as massive as a large planet."

The blazar jets are running around the universe in some fast company. Slightly faster, in fact.

In another study presented at the meeting, ultra high-energy cosmic rays thought to originate in a collision of galaxy clusters are slamming into Earth's atmosphere at more than 99.9 percent of the speed of light. Measurements put the number at 99.9 followed by 19 more nines -- about as close to light-speed as you can get without splitting hairs.

The particles are not light, but actual matter. They are tiny, thought to be mostly protons, but the energy that motivates them is similarly fantastic, and the mechanisms may be intertwined.

Scientists still don't know the exact mechanisms involved in accelerating matter to such high speeds, however. In the case of a blazars, it appears a black hole is involved. Anchoring an active galaxy, a supermassive black hole draws gas inward. Some is swallowed, yet some is simply accelerated and then ejected in high-speed jets along the galaxy's axis of rotation. Intense, twisted magnetic fields may play a role.

Some ultra high-energy cosmic rays might originate in blazar jets, Piner told But other phenomena may serve as particle accelerators in space, such as merging galaxies or colliding black holes.

Piner and his colleagues observed three blazars, known from previous observations to be super speedy, using the National Science Foundation's Very Long Baseline Array radio observatory.

The results confirm the previous work and pin down the speeds with greater accuracy. The phenomenal pace of the plasma blobs looks to have reached a limit.

"All the results from blazar jet observations are in agreement with Einstein's Theory of Special Relativity," Piner said. "The jets are accelerated right up to the edge of the speed-of-light barrier but not beyond, even though these are some of the most efficient accelerators in the universe."

Scientists Find Missing Matter


Scientists Find Missing Matter

By Amit Asaravala

02:00 AM Feb. 03, 2005 PT

For years, astrophysicists have been boggled by the fact that the grand sum of all the known "normal" matter in the universe -- that which makes up the stars, the Earth and even our own bodies -- only amounts to half of what should exist based on computer simulations.

Given that multiple simulations have continually yielded the same result, they theorized that the rest of the normal matter, known as baryons, must be hiding somewhere in the space between galaxies. However, they haven't had much evidence to support the theory until now.

Astrophysicists used the Chandra X-ray Observatory to detect traces of 'normal' matter known as baryons floating between galaxies. The intergalactic baryons are too hot and too diffuse to be detected by optical telescopes.

A new study conducted with the help of the Earth-orbiting Chandra X-ray Observatory has revealed the existence of baryons in at least two giant, intergalactic clouds of super-hot gas 150 million and 380 million light-years from our planet.

The study, which appears in the Feb. 3 issue of the journal Nature, shows how certain wavelengths of X-rays emitted from a distant galaxy in the constellation Ursa Major are being absorbed by the two clouds. The absorption pattern, as detected by Chandra, is consistent with interference caused by carbon, neon, nitrogen and oxygen ions -- in other words, baryons.

When the study's authors extended the number of baryons in the two clouds to account for the volume of all the intergalactic clouds in the universe, the resulting figure equaled that of the missing matter from their computer simulations.

"Assuming that what we see is a standard portion of the universe, we extrapolated the data and derived the volume density (of baryons in all the clouds) -- and it's consistent with 50 percent," said astronomer Fabrizio Nicastro, of the Harvard-Smithsonian Center for Astrophysics and lead author of the study.

The findings extend the reach of a similar study published by Nicastro and his colleagues in 2003. In that research, the scientists discovered baryons between galaxies in the Local Group, a selection of 30 galaxies near to, and including, our own Milky Way. But astrophysicists weren't sure at the time if the data would apply to intergalactic spaces outside the Local Group, so they kept searching.

Even with the new evidence, they plan to keep looking, said Nicastro. That's because intergalactic baryons not only fill a gap in scientists' understanding of the universe, but they may also lead to a better understanding of "dark matter," a mysterious and unseen form of matter that has so far only been detected by the gravitational pull it exerts on other bodies in the universe.

"If we are right, each single one of these filaments is connected to a cloud of dark matter," said Nicastro. "If there wasn't dark matter there, or something with strong gravity that pulled on the matter in these filaments, we wouldn't have galaxies or filaments." Rather, the baryons would be pulled into galaxies and the galaxies into each other.

Whereas baryons account for 4 percent of the total matter and energy in the universe, dark matter is thought to make up 23 percent. The remaining 73 percent of the so-called matter-energy budget consists of what scientists call "dark energy." This energy acts like an anti-gravitational force that, in theory, is causing the universe to expand rather than contract.

Nicastro and his team used the Chandra X-ray Observatory to search for traces of the baryons because X-ray light from space does not reach Earth-based telescopes. They are too hot and too diffuse in the intergalactic clouds to be detected by optical telescopes.

Chandra was released from the space shuttle Columbia in 1999.

NASA is currently developing a series of four satellites known as Constellation-X that would enhance astronomers' ability to study baryons, dark matter and dark energy. It is expected to launch no sooner than 2015.

End of story,2697,66487,00.html

anome said:
You slow down with gravitational capture, and maybe aerobraking.

By the way, interesting to see Greg Benford involved. And the similarities between this and the solar sail used in Rocheworld by Robert L. Forward.

Noticed the similiarity meself...
Aerobraking... might be a bit 'messy'
I'm rather upset about this :x Surely Hubble's got many more years service left.

Nasa plans to bring down Hubble

The Hubble Space Telescope and a mission to explore Jupiter's moons look to be the biggest casualties in Nasa's 2006 budget plans outlined on Monday. Under the proposals, a mission to service Hubble would be scrapped and the telescope left to die in orbit.

Nasa's total budget would rise 2.4% over 2005 to about $16.5bn, but only $93m would be spent on Hubble.

About $75m of that will be aimed at bringing the observatory down to Earth safely, officials have announced.

The US space agency (Nasa) has fared better than many government agencies in President George Bush's 2006 budget request. But the White House is not seeking as much money for the space agency as had previously been planned - and that is bad news for Hubble.

"Hubble is a spacecraft that is dying," Nasa comptroller Steve Isakowitz said at a briefing in advance of the budget's release.

"We have decided that the risks associated with the Hubble servicing at this time don't merit going forward."

This will infuriate Hubble supporters who believe the telescope still has good years of science observation ahead of it - provided it is serviced.

They will hope Congress, which has to approve the budget, will insist on money being found to save the orbiting observatory.

"There is a long history of Congress putting into the Nasa budget what Nasa or the executive branch don't like and have taken out," said Rodger Thompson, a University of Arizona astronomer and principal investigator of the Near-Infrared Camera and Multi-Object Spectrometer (Nicmos), which astronauts placed on Hubble in 1997.

"The Gravity Probe-B was cancelled many times and each time was put back in the budget by Congress.

"There is going to be a large debate about this and there is a significant chance that funding for Hubble will be returned to the budget," he told the BBC News website.

The multi-billion dollar Jupiter Icy Moons Orbiter (Jimo) mission was to have been launched in about 2015 as a demonstration for the Project Prometheus nuclear power and propulsion initiative.

It would have gone into orbit around the giant planet and its moons, possibly putting landers on their surfaces in much the same way as Cassini has done with Huygens on Titan.




Bubble bursts for pioneer Hubble

Tim Radford, science editor
Tuesday February 8, 2005
The Guardian

It watched the broken pieces of a comet crash, one after another, into the clouds of Jupiter. It peered at a dark patch of sky no bigger than a grain of sand at arm's length for 150 orbits and spotted so many galaxies that cosmologists had to double their estimates of the size of the universe.

It confirmed the existence of black holes and caught stars in the act of formation. Its astonishing images have become the stuff of poster art and gallery displays.

But the Hubble space telescope, which orbits the planet 360 miles above the clouds and atmosphere, could soon plunge to Earth and perish in a fireball over the Pacific Ocean.

Nasa chiefs last night confirmed that their budget rise for 2006 would not be enough to cover the cost of a repair mission to the 14-year-old instrument. The US space agency will have $16.5bn (£8.9bn) to spend, but only $75m to spend on Hubble. This is just about enough for a robot spacecraft that could rendezvous with the world's most famous telescope and nudge it back into the deadly embrace of the planet's gravitational field.

The decision is likely to infuriate astronomers: last year the US National Academy of Sciences urged a final visit by a team of astronauts to Hubble, to replace parts likely to wear out in a year or two.

Hubble was launched in a blaze of glory that turned to tragicomedy: when the telescope returned its first snaps of the heavens, researchers discovered faulty curvature in its 2.4 metre mirror.

In 1993, astronauts went aloft and fitted the equivalent of spectacles, and suddenly Hubble revealed its astonishing capacity: it could resolve galaxies 13bn light years away, at the edge of space and time.

But techniques in Earth-based astronomy advanced, and British astronomers now use a telescope in Hawaii twice as powerful as Hubble.

Nasa began looking for ways to save money. "We have been as eager as the Congress to try to save the Hubble, but at the end of the day what we're trying to save is the science related to Hubble," said Nasa's controller, Steve Isakowitz.,12996,1408049,00.html

Star Wants Out of Milky Way


Star Wants Out of Milky Way

By Amit Asaravala

02:00 AM Feb. 09, 2005 PT

A star three times bigger than the sun has been seen fleeing our galaxy at over 1.5 million mph, according to astronomers at the Harvard-Smithsonian Center for Astrophysics.

The gravitational pull of a black hole thought to exist there is likely responsible for the extreme velocity of the star, swinging it around the center of the Milky Way. A companion star may once have traveled with the speeding star and contributed to its velocity before being trapped by the black hole.

Planets are thought to be formed from disks of dust and gas, like the one shown orbiting a brown dwarf star in this artist's rendering. Astronomers have announced the discovery of such a disk around the smallest brown dwarf yet to be found.Astronomers have discovered a star traveling over 1.5 million mph -- fast enough to escape the gravitational pull of the Milky Way galaxy. This image from the Sloan Digital Sky Survey shows an area of the sky one-fiftieth the size of the full moon (the arrow marks the star).

The first-of-its-kind finding not only confirms an earlier theory about the existence of such speeding stars, but also reinforces the notion that the Milky Way spins around a black hole, said Warren Brown, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics and a member of the team that discovered the star.

"It's a hypothesis on our part, but there's no other good way of explaining a star moving this fast," said Brown. "The only way to get velocity that high on a star is you have to interact with something more extreme, like a black hole."

The star is currently 180,000 light years from Earth. Based on its trajectory, the astronomers believe it will exit the Milky Way and scream through miles of empty space until it burns out.

"The space between galaxies is extremely empty," said Brown. "It will have a nice view of the Milky Way for a while. At some point, the night sky from that star would look like a couple big galaxies. But everything else would be pure black.",2697,66542,00.html

Another report on this:

Outcast star quits the Milky Way

Wednesday, February 9, 2005 Posted: 0629 GMT (1429 HKT)

WASHINGTON (Reuters) -- A star is zooming out of the Milky Way, the first seen escaping the galaxy, astronomers have reported.

The so-called "outcast star" is heading for the emptiness of intergalactic space after being ejected from the heart of the Milky Way following a close encounter with a black hole, said Warren Brown, an astronomer at the Harvard-Smithsonian Center for Astrophysics.

It is going so fast -- over 1.5 million mph (2.4 million km/h) -- that astronomers believe it was lobbed out of the galaxy by the tremendous force of a black hole thought to sit at the Milky Way's center.

That speed is about twice the velocity needed to escape the galaxy's grip, Brown said by telephone.

"We have never before seen a star moving fast enough to completely escape the confines of our galaxy," he said.

"We're tempted to call it the outcast star because it was forcefully tossed from its home."

The star used to be part of a binary pair, waltzing with its companion star close to the rim of the black hole.

In this case, "close" is a relative term; the actual distance was probably about 50 times the 93 million mile (150 million km) distance between Earth and the sun.

As the two stars twirled around each other, they were pulled faster and faster toward the edge of the black hole, one of those monster drains in space whose gravity is so strong that nothing, not even light, can escape once it is consumed.

While the companion star was captured by the black hole, the outcast continued on its whirling path around its edge.

Objects go faster the closer they get to black holes and this star was probably moving at extraordinary speed, perhaps as high as 20 million mph (32 million km/h).

That very speed, coupled with the speed of its twirling, sent the star zooming toward the edge of the Milky Way and beyond.

At this point, the outcast is about 180,000 light-years from Earth, in an outer region of the galaxy known as the halo.

A light-year is about 6 trillion miles (10 trillion km), the distance light travels in a year.

Copyright 2005 Reuters.

Meshed theories could explain planet formation

Astronomers meshed a 50-year-old idea with a planet formation model from the 1990s to create a new model of how planets are created in the gaseous discs surrounding young stars.

"Maybe reality is just a little complicated and both things are happening at the same time," suggests astronomer Richard Durisen at Indiana University, Bloomington, US.

In the 1990s, the dominant model of how planets form was "core accretion". In this model, solid objects bump into one another and stick together in an early solar system. If an object grows to about 10 times the Earth's mass, it can become big enough to attract surrounding gas, possibly leading to the birth of a gaseous giant planet.

But that process may be too slow to be a realistic explanation of how gas giants form, Durisen says. And it probably would not work for the formation of the "super Jupiter" planets spotted around other stars. "It's hard enough just to make Jupiter in a reasonable amount of time," Durisen told New Scientist. Super Jupiters are estimated to be several times the mass of Jupiter.

Torn apart
Another possible explanation for planetary formation - the "gravitational-instability model" - was first proposed over half a century ago. In this, a spinning cloud of gas, dust and ice around a star collapses into a disc and forms spiral arms. Those arms then break into clumps that grow until planets form. "It's like a little seed that keeps growing on the disc," says Scott Kenyon, an astronomer at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, US.

But this method comes with its own problems. When computer models create these clumps, they are often torn apart by the violent, spinning system.

Now Durisen and his colleagues suggest that even if the gravitational instabilities in an infant solar system do not lead to permanent clumps, the instabilities may speed up core accretion.

In their hybrid computer simulation, dense gas rings form at the border of stable and unstable areas of the spinning disc. The gas is hot inside the border but cold outside, and the cold gas is drawn inward until it hits the wall of hot gas.

Once enough gas builds up in the ring, it draws in solid material through its own gravity. Eventually, the core accretion model could kick in, and material in the ring could begin to coalesce into a planet. And each solar system could have more than one ring, according to the model, so more planets would be a possibility.

The study will be published in the February issue of the Icarus.

"Huge 'star-quake' rocks Milky Way

Astronomers say they have been stunned by the amount of energy released in a star explosion on the far side of our galaxy, 50,000 light-years away.

The flash of radiation on 27 December was so powerful that it bounced off the Moon and lit up the Earth's atmosphere.

The blast occurred on the surface of an exotic kind of star - a super-magnetic neutron star called SGR 1806-20.

If the explosion had been within just 10 light-years, Earth could have suffered a mass extinction, it is said.

"This is a once-in-a-lifetime event"
Dr Rob Fender, Southampton University

"We figure that it's probably the biggest explosion observed by humans within our galaxy since Johannes Kepler saw his supernova in 1604," Dr Rob Fender, of Southampton University, UK, told the BBC News website.

One calculation has the giant flare on SGR 1806-20 unleashing about 10,000 trillion trillion trillion watts.

"This is a once-in-a-lifetime event. We have observed an object only 20km across, on the other side of our galaxy, releasing more energy in a 10th of a second than the Sun emits in 100,000 years," said Dr Fender.

Fast turn

The event overwhelmed detectors on space-borne telescopes, such as the recently launched Swift observatory.

This facility was put above the Earth to detect and analyse gamma-ray bursts - very intense but fleeting flashes of radiation.

The giant flare it and other instruments caught in December has left scientists scrabbling for superlatives.

Swift moved quickly to track down the source of the gamma-rays
Twenty institutes from around the world have joined the investigation and two teams are to report their findings in a forthcoming issue of the journal Nature.

The light detected from the giant flare was far brighter in gamma-rays than visible light or X-rays.

Research teams say the event can be traced to the magnetar SGR 1806-20.

This remarkable super-dense object is a neutron star - it is composed entirely of neutrons and is the remnant collapsed core of a once giant star.

Now, though, this remnant is just 20km across and spins so fast it completes one revolution every 7.5 seconds.

"It has this super-strong magnetic field and this produces some kind of structure which has undergone a rearrangement - it's an event that is sometimes characterised as a 'star-quake', a neutron star equivalent of an earthquake," explained Dr Fender.

"It's the only possible way we can think of releasing so much energy."

Continued glow

SGR 1806-20 is sited in the southern constellation Sagittarius. Its distance puts it beyond the centre of the Milky Way and a safe distance from Earth.

"Had this happened within 10 light-years of us, it would have severely damaged our atmosphere and would possibly have triggered a mass extinction," said Dr Bryan Gaensler, of the Harvard-Smithsonian Center for Astrophysics, who is the lead author on one of the forthcoming Nature papers.

"Fortunately there are no magnetars anywhere near us."

The initial burst of high-energy radiation subsided quickly but there continues to be an afterglow at longer radio wavelengths.

This radio emission persists as the shockwave from the explosion moves out through space, ploughing through nearby gas and exciting matter to extraordinary energies.

"We may go on observing this radio source for much of this year," Dr Fender said.

This work is being done at several centres around the globe, including at the UK's Multi-Element Radio-Linked Interferometer Network (Merlin) and the Joint Institute for VLBI (Very Long Baseline for Interferometry) in Europe - both large networks of linked radio telescopes. "
Magnetars are disturbingly unusual;
the magnetic field is so strong that it stretches the neutrons and the thin crust of non-degenerate atoms so much that they are a hundred times as long as they are wide.
That magnetar is more than a little wierd. As I understand it, the fact that is did not slow down after the emission of so much energy puts the hypothoses on how they "work" into doubt
'Pack ice' suggests frozen sea on Mars

'Pack ice' suggests frozen sea on Mars
11:48 21 February 2005 news service
Kelly Young
A frozen sea, surviving as blocks of pack ice, may lie just beneath the surface of Mars, suggest observations from Europe's Mars Express spacecraft. The sea is just 5° north of the Martian equator and would be the first discovery of a large body of water beyond the planet's polar ice caps.

Images from the High Resolution Stereo Camera on Mars Express show raft-like ground structures - dubbed "plates" - that look similar to ice formations near Earth's poles, according to an international team of scientists.

But the site of the plates, near the equator, means that sunlight should have melted any ice there. So the team suggests that a layer of volcanic ash, perhaps a few centimetres thick, may protect the structures.

"I think it's fairly plausible," says Michael Carr, an expert on Martian water at the US Geological Survey in Menlo Park, California, who was part of the team. He says scientists had previously suspected there was a past water source north of the Elysium plates. "We know where the water came from," Carr told New Scientist. "You can trace the valleys carved by water down to this area."

He says the evidence is "compelling" for past flooding near the plates. "Maybe the ice is still there in the ground, protected by a volcanic cover, as they suggest," he says.

There is abundant evidence for the past presence of water on Mars but today it appears relatively dry, with water ice confined to the planet's polar caps. Remote observations of hydrogen atoms by NASA's Odyssey spacecraft in 2002 hinted that ice might be locked in the top metre of soil at lower latitudes. But the evidence was inconclusive as the signal could have come from minerals exposed to water in the past.

45 metres deep
The team of researchers, led by John Murray at the Open University, UK, estimates the submerged ice sea is about 800 by 900 kilometres in size and averages 45 metres deep. Images of the pack-ice-like plates can be seen in this PDF document, which was not embargoed when New Scientist first viewed it on 15 February.

The paper is for a presentation to be made at the Lunar and Planetary Science Conference in Texas on March 18. A talk with the same title is scheduled to be given by Murray at the 1st Mars Express Science Conference in Noordwijk, the Netherlands, today.

The team arrived at the depth estimate by studying craters in the plates. They say the craters appear too shallow for their diameters - suggesting ice is filling them up. Moreover, the surface appears unusually level - as if ice were beneath it. This evidence suggests the plates are not just imprints left by ice that has now completely vanished. Crater counts indicate the age of the plates is about 5 million years.

In their paper, the researchers trace a possible history for the underground ice. It begins with huge masses of ice floating in water on Mars. The ice was later covered with volcanic ash, preventing it from sublimating away into the thin atmosphere. Then, the ice broke up and drifted before the remaining liquid water froze. All of the ice not protected by ash sublimated away, leaving the pack ice plates behind.

"If the reported hypothesis is true, then this would be a prime candidate landing site to search for possible extant life on Mars," says Brian Hynek, a research scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder, US.

Lava flow
One problem with this proposed frozen sea is that there is very little water vapour in the Martian atmosphere today. Carr says that if there had been relatively recent sublimation, as the scientists propose, some traces of water should remain in the atmosphere.

Also, similar plate formations have been seen on Mars before but attributed to solidified lava. But Murray's team says a lava flow does not fit their observations. These plates are up to two times larger than known lava plates on Earth, and they leave behind smooth, straight lanes when they ram into craters and islands. These observations "imply an extremely mobile fluid, with similar characteristics to water," the researchers write.

Carr says there are other regions on Mars with similar plate formations, meaning this might not be the only subterranean water. But ultimately, it may be difficult to prove whether the frozen sea still exists today.

The MARSIS radar, which will soon be deployed on Mars Express, should be able to detect underground liquid water but may have trouble differentiating between ice and rocky soil. And the ice is not visible directly. "To preserve it, you've got to bury it," Carr says. "But if you bury it, you can't detect it."

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Mars Express 'divining rod' mission delayed
08 October 2004
Mars Express, European Space Agency
Lunar and Planetary Science Conference
1st Mars Express Science Conference
John B Murray, The Open University
Are pulsars gravity-wave generators?

Are pulsars gravity-wave generators?
By Lucy Sherriff
Published Tuesday 22nd February 2005 17:32 GMT
Scientists at the European Space Agency (ESA) say that a newly discovered star could provide a test for the existence of gravitational waves.

The object, a pulsar, was discovered by the INTEGRAL spacecraft, and is one of the fastest spinning stars ever seen, rotating nearly 600 times every second. Most millisecond pulsars hover around the 300 revolutions per second mark, and the fastest spinning pulsar ever detected clocked in at 641 rps.

But even this is far short of the theoretical maximum of around 3,000 revolutions per second. Any faster that this and the object would tear itself apart. "Nature is applying some kind of brake, but we don't know what that is," MIT's Deepto Chakrabarty told New Scientist

Theoretically, a spinning body's speed should be limited by gravitational waves, the researchers say, which would carry energy away in the form of ripples in spacetime. Rapidly rotating, uneven objects are predicted to generate these waves, with faster spinning bodies creating more waves than slower ones.

The pulsar was discovered by a research team at the University of Southampton, and the findings are published in Astronomy & Astrophysics. As more super-fast millisecond pulsars are discovered, researchers will be able to tell if gravitational waves really are at work.

Chakrabarty explains that if there is a bunching of pulsars at and around the 600rps mark, this would suggest that gravitational waves are indeed involved. But if the upper speed limit tails off more gradually, then other factors are more likely responsible.

But researchers will have to wait for the upgrades to the Laser Interferometer Gravitational Wave Observatory (LIGO), to be complete before they can say for sure. These will be finished in 2008, and will be sensitive enough to detect any gravitational waves emanating from a pulsar.


Astronomers find star-less galaxy

Astronomers say they have discovered an object that appears to be an invisible galaxy made almost entirely of dark matter.

The team, led by Cardiff University, claimed it is the first to be detected.

A dark galaxy is an area in the Universe containing a large amount of mass that rotates like a galaxy, but contains no stars.

It was found 50 million light years away using radio telescopes in Cheshire and Puerto Rico.

The unknown material that is thought to hold these dark galaxies together is known as 'dark matter', but scientists still know very little about what that is.

The five-year research has involved studying the distribution of hydrogen atoms throughout the Universe, estimated by looking at the rotation of galaxies and the speed at which their components moved.

Hydrogen gas releases radiation that can be detected at radio wavelengths.

In the Virgo cluster of galaxies, they found a mass of hydrogen atoms a hundred million times the mass of the Sun.

The Universe has all sorts of secrets still to reveal to us, but this shows that we are beginning to understand how to look at it in the right way
Dr Jon Davies

The mysterious galaxy has been called VIRGOHI21.

Similar objects that have previously been discovered have since turned out to contain stars or be remnants of two galaxies colliding.

However, the scientists from the UK, France, Italy and Australia found no visible trace of any stars, and no galaxies nearby that would suggest a collision.

Dr Robert Minchin, of Cardiff University, said: "From its speed, we realised that VIRGOHI21 was a thousand times more massive than could be accounted for by the observed hydrogen atoms alone.

"If it were an ordinary galaxy, then it should be quite bright and would be visible with a good amateur telescope."

The astronomers say it is hard to study the universe's dark, hidden objects because of the Earth's proximity to the Sun.

They liken it to looking out at the darkest night from a well-lit room - it is easy to make out street lights but not trees, hedges and mountains.

Astronomers say it marks an important breakthrough because, according to cosmological models, dark matter is five times more abundant than the ordinary (baryonic) matter that makes up everything we can see and touch.

Another of the Cardiff team, Dr Jon Davies, added: "The Universe has all sorts of secrets still to reveal to us, but this shows that we are beginning to understand how to look at it in the right way. It's a really exciting discovery."

Sorry about replying to my own post, but I forgot to add this :oops:

Why don't we see any on-going mergers between invisible and visible galaxies. If they are so common (5 times more dark than normal matter) surely we should be seeing gravitationally driven mergers actually happening out there. We already see a fair number of mergers underway between two visible galaxies, but why not a severely distorted visible galaxy that is merging with an invisible dark matter galaxy :?:
Another version, but now it's the "Invisible Galaxy":

First Invisible Galaxy Discovered in Cosmology Breakthrough

Robert Roy Britt

Astronomers have discovered an invisible galaxy that could be the first of many that will help unravel one of the universe's greatest mysteries. The object appears to be made mostly of "dark matter," material of an unknown nature that can't be seen. Theorists have long said most of the universe is made of dark matter. Its presence is required to explain the extra gravitational force that is observed to hold regular galaxies together and that also binds large clusters of galaxies.

Theorists also believe knots of dark matter were integral to the formation of the first stars and galaxies. In the early universe, dark matter condensed like water droplets on a spider web, the thinking goes. Regular matter -- mostly hydrogen gas -- was gravitationally attracted to a dark matter knot, and when the density became great enough, a star would form, marking the birth of a galaxy.

The theory suggests that pockets of pure dark matter ought to remain sprinkled across the cosmos. In 2001, a team led by Neil Trentham of the University of Cambridge predicted the presence of entire dark galaxies.

One of perhaps many

The newfound dark galaxy was detected with radio telescopes. Similar objects could be very common or very rare, said Robert Minchin of Cardiff University in the UK. "If they are the missing dark matter halos predicted by galaxy formation simulations but not found in optical surveys, then there could be more dark galaxies than ordinary ones," Minchin told

In a cluster of galaxies known as Virgo, some 50 million light-years away, Minchin and colleagues looked for radio-wavelength radiation coming from hydrogen gas. They found a well of it that contains a hundred million times the mass of the Sun. It is now named VIRGOHI21. The well of material rotates too quickly to be explained by the observed amount of gas. Something else must serve as gravitational glue. "From the speed it is spinning, we realized that VIRGOHI21 was a thousand times more massive than could be accounted for by the observed hydrogen atoms alone," Minchin said. "If it were an ordinary galaxy, then it should be quite bright and would be visible with a good amateur telescope."

The ratio of dark matter to regular matter is at least 500-to-1, which is higher than I would expect in an ordinary galaxy," Minchin said. "However, it is very hard to know what to expect with such a unique object -- it may be that high ratios like this are necessary to keep the gas from collapsing to form stars."

Long road to discovery

Other potential dark galaxies have been found previously, but closer observations revealed stars in the mix. Intense visible-light observations reveal no stars in VIRGOHI21. The invisible galaxy is thought to lack stars because its density is not high enough to trigger star birth, the astronomers said. The discovery was made in 2000 with the University of Manchester's Lovell Telescope, and the astronomers have worked since then to verify the work. It was announced today.

"The universe has all sorts of secrets still to reveal to us, but this shows that we are beginning to understand how to look at it in the right way," said astronomer Jon Davies of Cardiff University in the UK. It's a really exciting discovery." Additional radio observations were made with the Arecibo Observatory in Puerto Rico. Follow-up optical work was done with the Isaac Newton Telescope in La Palma. Astronomers from the UK, France, Italy and Australia contributed to the research. The project is now searching for other possible dark galaxies.

Dark matter makes up about 23 percent of the universe's mass-energy budget. Normal matter, the stuff of stars, planets and people, contributes just 4 percent. The rest of the universe is driven by an even more mysterious thing called dark energy.

Gyro sacrifice may extend Hubble's life

Engineers are testing whether the Hubble Space Telescope should clip its own wings in an attempt to survive as long as possible without a servicing mission. Preliminary results suggest the new, scaled-down operating mode will buy the telescope an extra year of life - possibly until the end of 2008 - without sacrificing too much science.

The telescope was originally designed to use three of its six gyroscopes to point and stabilise itself in space. But these devices regularly break down - astronauts have replaced them twice. Now, the 15-year-old observatory has only four working gyroscopes - including one in "standby" mode in case of another failure.

Unless the US Congress intervenes or NASA reverses course, the telescope will have to rely on those four gyros for as long as possible before a robot is sent up to "de-orbit" the telescope - sending it crashing safely into the ocean.

The agency cancelled a shuttle mission to Hubble in January 2004, citing astronaut safety in the wake of the Columbia disaster in February 2003. And departing NASA chief Sean O'Keefe recently called off efforts to service the telescope with robots on the grounds that such a mission seemed too ambitious to succeed.

Fortunately, engineers at NASA foresaw trouble after the Columbia accident and began work on software that would allow the telescope to run on only two gyros, making the third a further standby. From 20 to 23 February, they conducted the first full-scale test of the new system by using data from only two gyros.

Jitter bugs
"When the engineers started writing the software, they had grave doubts," says Edward Weiler, director of NASA's Goddard Space Flight Center in Greenbelt, Maryland, US. "But I just got a report the test worked so well it's almost embarrassing. It's a real success story."

He says images snapped during the test were "almost indistinguishable" from those taken during regular, three-gyro operations. That has been one of scientists' main concerns about switching to a two-gyro system - that "jitter" in the telescope would produce blurry, oval-shaped images rather than circular ones.

Another concern has a larger potential impact on astronomical research. In lieu of a third gyroscope, Hubble must use star "trackers" to point toward its targets. But these trackers "look out in a different direction from the telescope tube", says Rodger Doxsey, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, which schedules Hubble observations.

That means Hubble cannot make observations when Earth gets in the trackers' field of view - an effect that will probably halve the number of days the telescope can observe any given object. "The flexibility for scheduling is reduced," he says, but adds that Hubble will still operate 24 hours a day.

Pessimist or optimist
Scientists will analyse the new test data for about a month. Then mission managers will make a decision about turning one of the working gyros off - which would probably occur in mid-2005 - and letting Hubble live out the rest of its days on two gyros.

That may postpone its demise for up to a year, until 2007, or possibly even late 2008 - depending on whether you are a pessimist or an optimist, says Weiler. Doxsey agrees there is uncertainty: "It's like predicting when your car might die."

Astronomers are anxious to maximise their remaining time with the space telescope. "Hubble is still doing the best astronomy in the world, so we want to continue as long as we can," Weiler told New Scientist.
Leaking Gravity May Explain Cosmic Puzzle


Leaking Gravity May Explain Cosmic Puzzle
By Sara Goudarzi
Special to
posted: 28 February 2005
06:28 am ET

WASHINGTON, D.C. - Scientists may not have to go over to the dark side to explain the fate of the universe.

The theory that the accelerated expansion of the universe is caused by mysterious "dark energy" is being challenged by New York University physicist Georgi Dvali. He thinks there's just a gravity leak.

Scientists have known since the 1920s that the universe is expanding. In the late 1990s, they realized that it is expanding at an ever-increasing pace. At a loss to explain the stunning discovery, cosmologists blamed it on dark energy, a newly coined term to describe the mysterious antigravity force apparently pushing galaxies outward.

This repulsive, unknown force is believed to make up more than 70 percent of the mass-energy budget of the universe.

But the existence of dark energy is far from proven, and some researchers believe they and their colleagues simply don't understand gravity at larger scales. The gravitational pull between any two objects becomes less with distance. But in Dvali's view, it weakens more than standard theory predicts.

Dvali would modify the theory of gravity so that the universe becomes self-accelerating, eliminating the need for dark energy. He presented his work here earlier this month at the annual meeting of the American Association for the Advancement of Science.

Dvali borrows from string theory, which states that there are extra, hidden dimensions beyond the four we are familiar with: three directions and time. String theory suggests that gravitons -- hypothetical elementary particles transmitting gravitational forces -- can escape to other dimensions. Dvali says this would cause "leaks" in gravity over cosmic proportions, reducing gravitational pull at larger distances more than expected.

"The gravitons behave like sound in a metal sheet," says Dvali. "Hitting the sheet with a hammer creates a sound wave that travels along its surface. But the sound propagation is not exactly two-dimensional as part of the energy is lost into the surrounding air. Near the hammer, the loss of energy is small, but further away, it's more significant."

The effect is to alter the space-time continuum, speeding up universal expansion.

"Virtual gravitons exploit every possible route between the objects," Dvali said, "and the leakage opens up a huge number of multi-dimensional detours, which brings about a change in the law of gravity."

The speeding up of the universe suggest that Einstein’s laws of General Relativity, describing the interaction of space and matter, must be modified at large cosmic distances.

"It is this modification, and not dark energy, that is responsible for the accelerated expansion of the universe," Dvali concludes.

The idea might be testable.

Gravity leakage should create minor deviations in the motion of planets and moons. Astronauts on the Apollo 11 mission installed mirrors on the lunar surface. By shooting lasers at the mirrors, a reflected beam can be monitored from Earth to measure tiny orbital fluctuations. Dvali said deviations in the Moon's path around Earth might reveal whether gravity is really leaking away.

This article is part of's weekly Mystery Monday series.

I have heard a very similar theory as this, but being used to explain the many, many orders of magnitude difference between the Strong Nuclear, Weak Nuclear and Electro Magnetic forces. The theory went along the lines of IIRC:
There are many rolled up dimensions
Gravity is spread over all of them
Gravity only appears weak; in fact it is acting as strongly as all the others, it’s just that we only see our part of the multiverse.

They also implied that dark matter was actually gravity leakage from other dimensions back into us and suggested that gravity could be used as a communication method between universes in the multiverse.

It is interesting that one part of string theory could explain away Dark Energy and Dark Matter at a stroke. This is especially true and the Dark Energy/Matter is starting to look a bit like Phlogiston.
Telescope spots hidden galaxies


Scientists: Telescope spots hidden galaxies

Wednesday, March 2, 2005 Posted: 1:26 PM EST (1826 GMT)

LOS ANGELES, California (AP) -- NASA scientists said an infrared telescope peered deep into stardust and spotted hidden galaxies more than 11 billion light-years from Earth.

In a journal article this week, the scientists describe how the Spitzer Space Telescope was used to find the galaxies, the most luminous in the universe. The galaxies shine with light equivalent to 10 trillion suns but are too far away and too drenched in cosmic dust to be seen -- until now.

"We are seeing galaxies that are essentially invisible," said Dan Weedman of Cornell University, in Ithaca, New York, who co-authored an article on the discovery in Astrophysical Journal Letters.

By studying these galaxies, we'll get a better idea of our own galaxy's history," said lead author James Houck, also of Cornell.

The Spitzer infrared telescope, a $670 million mission launched in August 2003, is managed by NASA's Jet Propulsion Laboratory in Pasadena.

"Past infrared missions hinted at the presence of similarly dusty galaxies over 20 years ago, but those galaxies were closer. We had to wait for Spitzer to peer far enough into the distant universe to find these," said Weedman.,74493170,2315,f/

Mysterious limit on star size revealed

Stars cannot grow heftier than 150 times the Sun's mass, suggest observations from the Hubble Space Telescope.

Astronomers have no explanation for this apparent "glass ceiling" but the finding may affect models of how heavier elements such as oxygen and iron are created and delivered through space.

Most of the universe's stars are less massive than our Sun and live for tens of billions of years. But these dwarfs are not massive enough to produce significant amounts of heavier elements in their nuclear furnaces. These elements have been churned out by much rarer, more massive stars that burn brightly and die young, after only a few million years.

But astronomers are unsure of exactly how massive stars can get. Some theorists think there is no upper mass limit for stars - they may be able to grow through "runaway collisions" with other stars in crowded star clusters.

Currently, the most reliable observations suggest the heavy-weight champions are about 80 times the Sun's mass. However, a handful of observations suggest there may be stars with about 300 solar masses - but these could simply be several distant stars whose light has blended together.

Now, Donald Figer, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, has found a possible upper mass limit. He used Hubble to observe about a thousand stars in the most massive young star cluster in our galaxy, a collection of several thousand stars near the galactic centre called the Arches cluster.

The brightness of these stars, along with spectra of 50 of them revealing their elemental composition, confirmed that none of the stars weighed in at more than 150 solar masses. "We expected a bunch and we saw zero. That's a huge difference and it's impossible to explain it away," Figer told New Scientist.

Violent explosions
"Too many stars are missing," agrees Pavel Kroupa, an astrophysicist at the Sternwarte of the University of Bonn, Germany. He and colleagues discovered a similar limit - though with fewer observations - in a nearby galaxy's cluster. "This will now be a challenge to understand theoretically why there should be a limit at 150 solar masses. "

One possibility, he says, is that heavier stars did exist in the 2 million-year-old Arches cluster but have already died out. But that requires rethinking standard stellar evolution theories because the cluster does not appear to harbour hot, expanding gas clouds. These clouds are the trademark signatures of supernovae, the violent explosions thought to accompany the deaths of massive stars.

Kroupa says stars above 150 solar masses might simply implode, confining their energy into black holes. But Figer doubts this scenario, arguing that if ultra-massive stars have already sped through their lives, the most massive stars remaining in the cluster should themselves be closer to death than observations show.

Figer says the research may shed light on how heavy elements have spread through space, as the universe's first stars were probably massive. "Also, by understanding what massive stars are like nearby, we can better interpret the observations of faraway galaxies," he says.
tzb57r said:

Astronomers find star-less galaxy

Hold it just a cotton-pickin'minute here! Isn't the definition of "galaxy" something like "big collection of stars"? So isn't this a bit like saying "Trawlermen discover fishless shoal"?
If theories concerning the age of the universe are wrong, couldn't this just be a galaxy where all of the stars have burned out?
Galactic pancake mystery solved

Astronomers have figured out why a series of small galaxies surrounding the Milky Way are distributed around it in the shape of a pancake.

Theorists believed that the eleven dwarf galaxy companions should have a diffuse, spherical arrangement.

But a University of Durham team used a supercomputer to show how the galaxies could take the pancake form without challenging cosmological theory.

The results were presented at the UK National Astronomy Meeting.

According to cosmological theory, soon after the Big Bang, cold dark matter formed the first large structures in the Universe, which then collapsed under their own weight to form vast halos.

The gravitational pull of these halos sucked in normal matter, providing a focus for the formation of galaxies.

Galaxies are made up of small fragments that merge together bit by bit.

This process should leave a tightly bound galaxy at the core, surrounded by a diffuse sphere of smaller satellite galaxies.

So why the Milky Way's satellites are arranged on a flat circle has been a puzzle to astronomers ever since Donald Lynden Bell of Cambridge University published details of the phenomenon in 1982.

So puzzling, in fact, that astronomer Pavel Kroupa, at the University of Bonn, Germany, questioned whether the cold dark matter-driven process for galaxy formation was really correct.

Now, Noam Libeskind and Carlos Frenk, from the University of Durham, have used the Cosmology Machine supercomputer, based at the city's institution, to simulate the formation of a galaxy from its building blocks.

Six simulations carried out on the machine not only came up with the correct number of satellites but also showed the same pancake arrangement seen in the Milky Way.

"It explains a cosmic problem," Professor Frenk told the BBC News website. "If you sat down and thought about how the galaxy formed, you would never come up with the pancake.

"It's a major triumph for the cold dark matter model [of galaxy formation]."

Noam Libeskind now plans to conduct further simulations to investigate how common the formation of these cosmic pancakes really is.

The Royal Astronomical Society's National Astronomy Meeting is being held at the University of Birmingham.
Alien asteroid belt detected around Sun-like star

An alien asteroid belt may have been spotted circling a mature star nearby. The observations, made by NASA's Spitzer Space Telescope, reveal a dense ring of dust around the star that might arise from rocks colliding and smashing each other apart.

Alternatively, the dust could come from a “supercomet” almost the size of Pluto, said Charles Beichman of the California Institute of Technology in Pasadena, US, at a NASA news conference on Wednesday.

Beichman and his colleagues used Spitzer to observe more than 80 Sun-like stars, including one called HD69830, which lies 41 light years away. Its infrared spectrum suggested it has a thick disc of warm dust grains surrounding it. The dust could be produced in a busy asteroid belt if large rocks are colliding every 1000 years or so, replenishing the ring.

“These grains are probably the signpost of an asteroid belt around 25 times more massive than that orbiting our own sun,” says Beichman. The dust seems to lie inside an orbit equivalent to that of Venus, much closer to its star than our own asteroid belt, which lies between Mars and Jupiter.

Earlier observations had revealed asteroid belts around young, massive stars. But HD69830 is a mature star, about half the age of the Sun and with 20% less mass. If confirmed, the new asteroid belt would be the first detected around a star similar to the Sun.

Rubble shepherds
“We’re really interested in understanding more about the asteroid belts of mature stars, because they tell us more about our own sun and whether our own planetary system is the norm or exceptional,” says Beichman.

Astronomers say the amount of rubble is surprising because debris around stars tends to disperse over time. They suspect a giant planet might be trapping the rubble in orbit, just as Jupiter’s gravity shepherds rocks in our own asteroid belt into a series of bands.

However, so far there have been no direct sightings of any planets around HD69830. And if any existed in the warmer inner regions of the system, they would probably be hostile to life. They would be pelted with rubble and suffer mass extinctions of any life every million years or so, Beichman expects.

A second possibility is that the dust around HD69830 comes from a giant comet slowly boiling away near the star. But to generate so much dust, the comet would have to be at least 25 times bigger than comet Hale-Bopp, which blazed spectacularly through the skies in 1997. And the required close-in orbit would mean the comet would boil away relatively quickly, making this scenario rather far-fetched.

Beichman hopes future observations of the star by Spitzer and other telescopes will discover the true source of the dust by pinning down its detailed chemical make-up.
Beichman hopes future observations of the star by Spitzer and other telescopes will discover the true source of the dust by pinning down its detailed chemical make-up.

I think it's as likely to be the remains of two or three Autocratic Theologian planets that, upon discovering they weren't alone in the universe, spent about 20 (Terran) years wrangling with this thorny philosophical issue and then committed mass suicide using "planet busting" Atomics :)
New observations triple Andromeda's size

The Andromeda galaxy, the most familiar of all the starry pinwheels in the sky and the Milky Way's virtual twin, is three times the size astronomers had thought.

Astronomers used the Keck II telescope in Hawaii to make new observations of the motions of stars in the most distant outskirts of the spiral galaxy. They found the movement of this sparse smattering of far-flung stars is actually synchronised with the rest of the galaxy's stars, rotating in an orderly way around its galactic centre.

One of the research team, Scott Chapman at Caltech, California, US, says this means the disc of the galaxy is actually three times larger than had been thought - 220,000 light years across, instead of previous estimates of 70,000 to 80,000.

The stars surrounding Andromeda's spiral arms had been seen before, but astronomers had assumed they were captured fragments of other galaxies that would retain their own, essentially random, stellar motions.

Finding all these stars in an orderly rotation about our nearest galactic neighbour was very surprising, Chapman says. The next step will be to extend the work to see if this is a peculiarity of the Andromeda galaxy, or is characteristic of spiral galaxies in general, he said.

The findings are hard to reconcile with current theories and computer models of galaxy formation, according to Rodrigo Ibata of the Observatoire Astronomique de Strasbourg, France, and another member of the research team. "You just don't get giant rotating discs from the accretion of small galaxy fragments.”

The new work was reported on Monday at the American Astronomical Society meeting in Minneapolis.
Wouldn't this change the distance of the Andromeda galaxy too - I mean, if it's 3 times the supposed diameter, wouldn't it have to be further away to have appeared the same relative size?