Team detects dust around a primitive star

The more scientists understand the composition of the dust, the better they can understand how stars and galaxies evolve.
Provided by Cornell University, Ithaca, New York

January 16, 2009

A team of astronomers has observed dust forming around a dying star in a nearby galaxy. This observation gives a glimpse into the early universe and enlivens a debate about the origins of all cosmic dust.

Cornell University Research Associate Greg Sloan led the study, which was based on observations with NASA's Spitzer Space Telescope. The researchers used Spitzer's Infrared Spectrograph, which was developed at Cornell.

Dust plays a key role in the evolution of galaxies like our Milky Way. Stars produce dust - rich with carbon or oxygen - as they die. But less is known about how and what kind of dust was created in galaxies as they formed soon after the Big Bang.

Sloan and his colleagues observed dust forming around the carbon star MAG 29, located 280,000 light-years away in a smaller nearby galaxy called the Sculptor Dwarf. Stars more massive than the Sun end their lives as carbon stars, which are a rich source of dust in our galaxy.

The Sculptor Dwarf contains only 4 percent of the carbon and other heavy elements in the Milky Way, making it similar to primitive galaxies seen at the edge of the universe. Those galaxies emitted the light we now see soon after they and the universe formed.

"What this tells us is that carbon stars could have been pumping dust soon after the first galaxies were born," Sloan said.

Scientists have debated where the dust in the early universe comes from. Supernovae have been a favorite suspect, but they may destroy more dust than they create.

"While everyone is focused on the questions of how much and what kind of dust supernovae make, they may not have appreciated that carbon stars can make at least some of the dust we are seeing," Sloan said. "The more we can understand the quantity and composition of the dust, the better we can understand how stars and galaxies evolve, both in the early universe and right next door."

"Observing such stars as MAG 29 is not unlike using a time machine in which astronomers can catch glimpses of what the universe looked like billions of years ago," Sloan said.

"We haven't seen carbon-rich dust in this primitive of an environment before," Sloan said.



The Sculptor Dwarf galaxy, with the position of carbon star MAG 29 noted. Palomar Digitized Sky Survey

Source

Supermassive black holes not guilty of shutting down star formation




Galaxies stop forming stars long before their central supermassive black holes reach their most powerful stage, according to a team of Yale University astronomers. This discovery means the black holes can't be responsible for shutting down star formation.

Until recently, astronomers believed that active galactic nuclei (AGN) - the supermassive, energetic black holes at the centers of many young galaxies - were responsible for shutting down star formation in their host galaxies once they grew large enough. It was thought that AGN feed on the surrounding galactic material, producing enormous amounts of energy (expelled in the form of light) and heat the surrounding material so that it can no longer cool and condense into stars.

But new research shows that this shutting-down process appears to take place much earlier in the AGN's lifetime, well before it starts shining brightly. "This high-luminosity phase, when the AGN are at their biggest and brightest and most powerful, is not the phase responsible for the shutdown of star formation," said Kevin Schawinski, a postdoctoral associate in Yale's astronomy department and lead author of the study.

The researchers analyzed images of 177 galaxies taken by two different space telescopes to create a comprehensive view of galaxies with AGN, including galaxies with AGN obscured by the galaxy's dust and gas and galaxies that had an unobstructed view of the AGN from the Earth's vantage point.

Until now, some astronomers believed they couldn't see AGN in any galaxies that form stars because the light from the AGN is obscured by the galaxy's gas and dust. Schawinski and his team are the first to show that there are no bright AGN at the centers of star-forming galaxies.

By subtracting the light from the AGN, the team discovered that all galaxies with bright AGN had stopped forming stars several hundred million years earlier. "The key result is the finding that there is a lack of AGN in galaxies that are currently forming stars," said Meg Urry, head of the Yale team and director of the Yale Center for Astronomy and Astrophysics. "That tells us the AGN doesn't turn on until long after the stars stop forming."

"For the first time, we've measured a real delay between the end of star formation and the onset of a luminous AGN," said Schawinski. As for the real culprit responsible for shutting down star formation, "It's possible that an earlier, low-luminosity phase is responsible," Schawinski said. "Either way, this result shows that our previous understanding of how the shutting-down process works wasn't as simple as we thought."

Source: Astronomy.com

Large Quantities of Methane Being Replenished on Mars



Methane has been measured in large quantities in Mars atmosphere over several seasons, meaning Mars is active, either geologically or biologically. "We found methane," said Dr. Geronimo Villanueva from the NASA Goddard Space Flight Center, one member of a team of scientists reporting on their research at a press conference today at NASA Headquarters. "We can measure not only the methane, but where it is coming from and when it is being released." This is the first definitive detection of methane on Mars that includes maps identifying areas of active release. "Mars is active," said Michael Meyers, lead NASA scientist for the Mars Program, "but we don't know if it's because of biology or geology or both."

The methane on Mars was first detected in 1999, again in 2001 and 2003, which was widely reported, but not much was known about the origin or amount of the gas on Mars.

The research team found methane in the atmosphere of Mars by carefully observing the planet over several Mars years, and during all the Martian seasons with NASA's Infrared Telescope Facility, run by the University of Hawaii, and the W. M. Keck telescope, both at Mauna Kea, Hawaii.

Measurements were made using spectroscopy by which light is split into its individual wavelengths, and then the "fingerprint" of individual molecules can be identified. [...]

The origin of methane could either be geologic where water reacts with hot rock and produces methane gas which escapes through pores in the planet's surface in a process called serpentinization. Or it could be evidence of biology under the surface, where the methane generated by microbes could accumulate and then escape through the rocks. [...]

"We observed and mapped multiple plumes of methane on Mars, one of which released about 19,000 metric tons of methane," said Villanueva. "The plumes were emitted during the warmer seasons — spring and summer — perhaps because the permafrost blocking cracks and fissures vaporized, allowing methane to seep into the Martian air. Curiously, some plumes had water vapor while others did not," said Villanueva. The rate of release is about 1 pound per second or .6 kg per second.

"Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane in the northern hemisphere of Mars in 2003 indicates some ongoing process is releasing the gas," said Dr. Michael Mumma of NASA's Goddard Space Flight Center in Greenbelt, Md. "At northern mid-summer, methane is released at a rate comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, Calif." [...]

While the team reported on results from observations in 2003 and 2006, they said they were not at liberty to discuss findings from subsequent observations, as the work to decipher the findings is still being done. [...]

Source: Universe Today

Ring of Fire: Indian Ocean to See Solar Eclipse



PARIS (AFP) – A few lucky people in the Indian Ocean will be treated to a rare event on Monday when an annular solar eclipse will transform the Sun into a dark disc with a blazing ring-shaped corona around its rim.

In solar eclipses, the Moon moves between the Sun and Earth, casting its shadow on the terrestrial surface.

In an annular eclipse, a tiny shift in distance that results from celestial mechanics means the Moon does not completely cover the Sun's face, as it does in a total eclipse.

Instead, for those directly under the alignment, the Moon covers most of the Sun's surface, and a ring-like crown of solar light blazes from the edge of the disk.

For those watching from the fringe of the track, the Sun is partially obscured, as if a bite has been taken out of it.

According to veteran NASA eclipse-watcher Fred Espenak, the total eclipse track will run from west to east on Monday [January 26th, 2009] from 0606 GMT to 0952 GMT.

It will traverse the Indian Ocean and western Indonesia before petering out just short of Mindanao, the Philippines.

The partial eclipse will be seen in a much wider swathe, including the southern third of Africa, Madagascar, Australia, Southeast India, Southeast Asia and Indonesia.

It will be the only annular solar eclipse this year. The last was on 7 February, 2007, and after Monday, the next one will be on 15 January, 2010.

The big event for eclipse junkies this year is on July 22, when a total solar eclipse will be visible from India and China, the world's two most populous countries.

Source: Yahoo! News

NASA'S Fermi Telescope Unveils a Dozen New Pulsars

01.06.09

NASA's Fermi Gamma-ray Space Telescope has found 12 previously unknown pulsars (orange). Fermi also detected gamma-ray emissions from known radio pulsars (magenta, cyan) and from known or suspected gamma-ray pulsars identified by NASA's now-defunct Compton Gamma-Ray Observatory (green). Credit: NASA/Fermi/LAT Collaboration

GREENBELT, Md. -- NASA's Fermi Gamma-ray Space Telescope has discovered 12 new gamma-ray-only pulsars and has detected gamma-ray pulses from 18 others. The finds are transforming our understanding of how these stellar cinders work.

"We know of 1,800 pulsars, but until Fermi we saw only little wisps of energy from all but a handful of them," says Roger Romani of Stanford University, Calif. "Now, for dozens of pulsars, we're seeing the actual power of these machines."

A pulsar is a rapidly spinning and highly magnetized neutron star, the crushed core left behind when a massive sun explodes. Most were found through their pulses at radio wavelengths, which are thought to be caused by narrow, lighthouse-like beams emanating from the star's magnetic poles.

If the magnetic poles and the star's spin axis don't align exactly, the spinning pulsar sweeps the beams across the sky. Radio telescopes on Earth detect a signal if one of those beams happens to swing our way. Unfortunately, any census of pulsars is automatically biased because we only see those whose beams sweep past Earth.

"That has colored our understanding of neutron stars for 40 years," Romani says. The radio beams are easy to detect, but they represent only a few parts per million of a pulsar's total power. Its gamma rays, on the other hand, account for 10 percent or more. "For the first time, Fermi is giving us an independent look at what heavy stars do," he adds.

Pulsars are phenomenal cosmic dynamos. Through processes not fully understood, a pulsar's intense electric and magnetic fields and rapid spin accelerate particles to speeds near that of light. Gamma rays let astronomers glimpse the particle accelerator's heart.

"We used to think the gamma rays emerged near the neutron star's surface from the polar cap, where the radio beams form," says Alice Harding of NASA's Goddard Space Flight Center in Greenbelt, Md. "The new gamma-ray-only pulsars put that idea to rest." She and Romani spoke today at the American Astronomical Society meeting in Long Beach, Calif.

Astronomers now believe the pulsed gamma rays arise far above the neutron star. Particles produce gamma rays as they accelerate along arcs of open magnetic field. For the Vela pulsar, the brightest persistent gamma-ray source in the sky, the emission region is thought to lie about 300 miles from the star, which is only 20 miles across.

Existing models place the gamma-ray emission along the boundary between open and closed magnetic field lines. One version starts at high altitudes; the other implies emission from the star's surface all the way out. "So far, Fermi observations to date cannot distinguish which of these models is correct," Harding says.

Because rotation powers their emissions, isolated pulsars slow as they age. The 10,000-year-old CTA 1 pulsar, which the Fermi team announced in October, slows by about a second every 87,000 years.

Fermi also picked up pulsed gamma rays from seven millisecond pulsars, so called because they spin between 100 and 1,000 times a second. Far older than pulsars like Vela and CTA 1, these seemingly paradoxical objects get to break the rules by residing in binary systems containing a normal star. Stellar matter accreted from the companion can spin up the pulsar until its surface moves at an appreciable fraction of light speed.

NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

Francis Reddy
NASA's Goddard Space Flight Center

Source: NASA

Scientists want to test Galileo's remains
By Philip Pullella, Reuters | January 23, 2009


The tomb of astronomer Galileo at the Santa Croce basilica in Florence. Italian and British scientists hope to determine whether his vision problems affected his telescopic findings.

ROME - Italian and British scientists want to exhume the body of 16th-century astronomer Galileo for DNA tests to determine if his severe vision problems may have affected some of his findings.

The scientists told Reuters yesterday that DNA tests would help answer some unresolved questions about the health of the man known as the father of astronomy, whom the Vatican condemned for teaching that the Earth revolves around the sun.

"If we knew exactly what was wrong with his eyes we could use computer models to re-create what he saw in his telescope," said Paolo Galluzzi, director of the Museum of History and Science in Florence, the city where Galileo is buried.

Galileo, who lived from 1564 to 1642, is known to have had intermittent eye problems for the second half of his life and was totally blind for his last two years.

"There were periods when he saw very well and periods when he did not see very well," said Dr. Peter Watson, president of the Academia Ophthalmologica Internationalis and consultant to Addenbrooke's University Hospital, Cambridge.

Watson, who has studied Galileo's handwriting, letters, and portraits of the astronomer, suspects he may have had unilateral myopia, uveitis - an inflammation of the eye's middle layer - or a condition called creeping angle closure glaucoma.

Watson believes Galileo did not acquire eye problems by looking at the sun but by systemic illnesses, including an attack when he was young that left him temporarily deaf and caused bloody discharges and arthritis so severe he was bedridden for weeks.

He was under particular stress when he was tried for heresy by the Inquisition because the Copernican theory he supported conflicted with the Bible.

One of the "errors" that Galileo made, which Galluzzi suspects may have been attributed to his bad eyesight, is that he believed Saturn was not perfectly round but may have had an irregular, inflated side.

With his 20-power telescope and with his eyes in bad shape he might have mistaken Saturn's gaseous ring to surmise that it was formed of one planet with two moons as satellites.

"This was probably a combination of errors. He probably expected to find satellites and his eyesight may have contributed to some confusion," said Galluzzi.

Astronomers hit telescope jackpot
By Robert S. Boyd
McClatchy News Service
Published:
Friday, January 23, 2009 12:14 PM EST


Above, the team building the LSST, a large survey telescope being assembled at the Steward Observatory Mirror Lab in Tucson, Ariz., celebrates the successful casting of the telescope’s 27.5-foot-diameter mirror blank.


Holes drilled more than a mile deep in the ice at the South Pole will hold hundreds of detectors to track the course of high-energy cosmic particles streaming up from the far side of the Earth.

Astronomers this year are about to get a windfall of new and improved telescopes of unprecedented power with which to explore the universe.

The bonanza arrives 400 years after Galileo spied craters on the moon through the world’s first telescope.

Instruments coming on line in 2009 will let researchers see farther and more clearly than ever — perhaps even detect signs of life on another planet or an asteroid swooping dangerously close to Earth.

The telescopes will open new windows on the heavens by using different technologies and different wavelengths of light. They’ll be able to see things in the far ranges of ultraviolet, infrared or radio waves that are invisible in the narrow band of optical light.

“This year’s going to be huge,” said Julianne Dalcanton, an astronomer at the University of Washington in Seattle. “The new capabilities are going to be absolutely fabulous.”

The International Astronomical Union, an organization of about 10,000 professional astronomers, has named 2009 the International Year of Astronomy. That’s in honor of Galileo, who was accused of heresy by the Roman Catholic Church for insisting that the Earth moves around the sun.

“In 2009, we would like everybody on Earth to think at least once about the wonders of the universe,” said IAU President Catherine Cesarsky, a French astrophysicist.

Among telescopes projects under way in 2009 are:

u A major upgrade of the 19-year-old Hubble Space Telescope, including two advanced detectors that will vastly improve its vision for another five years.

u A bigger European rival to Hubble called the Herschel Space Observatory.

u ALMA, an array of 50-plus telescopes on a lofty desert in Chile that will be the most powerful ground-based observation system to date.

u Kepler, an orbiting telescope designed specifically to look for inhabitable planets around distant stars.

u Pan-STARRS, a set of four interconnected telescopes to detect fast-moving hazardous objects, such as satellites or space rocks.

u IceCube, an upside-down space particle observatory buried under the ice at the South Pole.

u The Allen Telescope Array, a set of 42 of radio telescopes listening for extra-terrestrial messages from possible civilizations around another star.

Waiting for future financing are even larger, more powerful machines, including two giant telescopes with light-collecting mirrors three to four times bigger than any existing telescope.

The larger of the two, the 140-foot-wide European Extremely Large Telescope, could make pictures of clouds, mountains and seas on distant planets. It’s now in the design stage, and construction might begin in 2010. Despite its huge size, it’s a scaled-down version of a 330-foot Overwhelmingly Large (OWL) telescope that was canceled for technical and cost reasons.

Another ground-based instrument, the Large Synoptic Survey Telescope (LSST) will take about 1,000 images of each spot in the entire sky over its lifetime. Taken together, the repeated images will produce color movies of celestial objects as they change or move, including potentially hazardous asteroids. The LSST can also trace changes in the expansion of the universe caused by the mysterious force known as dark energy. Work on the telescope mirror is under way, and it should start taking images in 2015.

The James Webb Space Telescope, NASA’s successor to Hubble, is under construction and scheduled for launch in 2013. Its main mirror, 21 feet in diameter, has to be folded up to fit in the launch vehicle, along with a sunshield that opens up to the size of a tennis court. JWST will orbit almost a million miles from Earth, where it will study the first stars and galaxies formed after the birth of the universe, 13.7 billion years ago. Unlike Hubble, JWST mostly will work in infrared light.

Here are main features of the new crop of telescopes:

Hubble

The Hubble Space Telescope, which was launched in 1990, will get a new lease on life when NASA launches the fifth and final shuttle mission to repair and upgrade its aging instruments. The launch is scheduled for May 12.

In addition, astronauts will install two devices — a Wide Field Camera and a Cosmic Origins Spectrograph — that will add fresh capabilities to the venerable Hubble.

“We estimate that at the end of this repair, Hubble will be 90 times more powerful than when it was first launched,” said Sandra Faber, an astronomer at the University of California, Santa Cruz.

Dalcanton, the University of Washington astronomer, is especially excited by the new spectrograph, a device that can determine the chemical makeup of a star and the atmosphere of an alien planet. This information is usually more valuable to scientists than a pretty image.

“An image tells us something’s there,” Dalcanton said. “Spectra tell us what kind of object it is, what it’s made of, and does it have an atmosphere.”

Herschel

On April 10, the European Space Agency is scheduled to launch the Herschel Space Observatory — a telescope that’s bigger and more powerful than Hubble is. Herschel’s main light-collecting mirror is 11.5 feet wide, one and a half times bigger than Hubble’s, and the largest mirror ever deployed in space.

Herschel will be parked 900,000 miles out in space, far beyond Hubble’s 350-mile, low-earth orbit, and will observe mostly in the far-infrared range, which Hubble doesn’t reach.

Piggybacking on the same launch rocket with Herschel will be the Planck Satellite, a European telescope that will survey the cosmic background radiation left over from the birth of the universe in greater detail than ever before.

Alma

Work is proceeding rapidly on the Atacama Large Millimeter Array — ALMA for short — an assembly of 66 huge antennas on the 16,500-foot-elevation Atacama desert in Chile. It’s one of the coldest, driest places on Earth, which minimizes atmospheric interference.

The first of its 100-ton antennas will be delivered to the site a year from now. Linked together by computers, they’ll collect radiation from objects in the coldest, deepest regions of space with 10 times the resolution of Hubble. ALMA may be able to observe the formation of planets around other stars.

Allen telescope

This array of 42 radio antennas near Mount Lassen in northern California will begin in March collecting extremely faint radio signals from space. Its sponsors hope to make the first detection of intelligent life beyond the solar system.

The search will concentrate on about 250,000 “promising target stars” near the center of the Milky Way galaxy, said Jill Tarter, director of the Center for SETI (Search for Extra-Terrestrial Intelligence) Research in Mountain View, Calif. Tarter, who’s the real-life basis for the Jodie Foster character in the movie “Contact,” has devoted her career to searching for alien civilizations.

“At first we will give highest priority to target stars that are known to host exo-planetary systems,” Tarter said. If more funds are found, the Allen array will be expanded to 350 antennas, hoping to catch a call from ET.

Kepler

The Kepler telescope, NASA’s alien planet hunter, is scheduled for launch on March 5 into an orbit that will trail behind the Earth as it circles the sun. It will spend three and a half years precisely measuring the brightness of 100,000 stars in the Milky Way.

Kepler will be looking for a slight dimming of a star’s light — evidence that a planet is crossing in front of it. The change in brightness will let scientists determine the size and orbit of the planet, which will show whether it might be able to support life. It’s the first mission specifically designed to detect Earth-like planets.

Icecube

This unusual telescope is nearing completion under the ice at the South Pole. Instead of looking up to the sky, IceCube looks down through Earth to detect high-energy cosmic particles called neutrinos, which are produced by exotic objects, such as black holes or galactic explosions, in deep space. Neutrinos are extremely hard to detect because they travel at almost the speed of light and can zip untouched through ordinary matter.

When finished in 2011, IceCube will consist of 70 long “strings,” each holding 60 light detectors, sunk in holes drilled a mile or more into the clear ice. The detectors will track neutrinos that have passed through the planet so scientists can determine their origin.

So far, 52 detector strings have been installed. Researchers began collecting data in April 2008.

A sensational, if unlikely, IceCube result would be the first strong evidence that the world contains extra dimensions — beyond the four familiar dimensions of space and time. Extra dimensions are a key part of “string theory,” currently the most fashionable version of the physical laws that govern the universe.

Astronomers try to solve mystery of bulging stars


In a new study, researchers present 3-D simulations of the formation of massive stars. This snapshot from the simulation shows a polar view of a star 55,000 years into its evolution.


Obesity has apparently reached galactic proportions, apparently — even stars have a problem with over-eating, a stellar mystery that has astronomers asking how some stars grow to be so large. A supercomputer scientist team may have the answer, in a demonstration of how nature can take something simple and make it complex.
About 7,500 light years away resides the star Eta Carinae, first noted in a star catalogue by the venerable astronomer Edmond Halley (best known for Halley's comet) in 1677. Since then, the star has bedazzled astronomers by brightening every century or so, most notably in an 1843 outburst that briefly made it the brightest star in the sky, despite its distance (one light year is about 5.9 trillion miles.) To add to the mystery, the star is a porker, about 120 times heavier than the sun, embedded in a star-forming gas cloud called the Carina Nebula.

University of California, Berkeley, astronomer Nathan Smith proposed last year in the journal Nature that 1843 outburst arose from an explosion deep in the star that spat out a blob of star-stuff perhaps ten times as heavy as the sun. The report counts the explosion as a newly-discovered mechanism for how gigantic stars, which only live a million years or so, start to break down prior to their final implosion (the process that forms black holes.)

But that left the bigger mystery, which is how do stars like Eta Carinae get so big in the first place? "We see stars at least 120 times that of the Sun throughout space, but the mechanism by which the most massive stars form is a longstanding mystery," says astronomer Mark Krumholz of the University of California, Santa Cruz. Astronomers know that stars form by the clumping together of gas clouds. These "proto-stars" ignite through nuclear fusion once they become about 80 times heavier than the planet Jupiter.

Stars are thereafter balancing acts, Krumholz explains, in which the inward pull of gravity from the center of a star fights against the outward "radiation pressure" from light and other electromagnetic radiation emitted by its nuclear furnace. Where the push and pull of the two forces balance out, you have the surface of the star.

For astronomers, all this works out nicely to produce young stars up to about 20 times heavier than the sun. But once the star grows larger, the math stops working and the radiation force pressure overwhelms the gravitational urge to pull in gas from outside the star. "But still, we see them, so they must grow somehow," Krumholz says.

So, to crack the mystery, he and his colleagues decided to grow their own super-massive star. Inside a rented super-computer, they programmed the simplest start for one, a circular cloud of gas about 100 times the weight of the sun. In the three-dimensional simulation, a first, the cloud collapsed into a circular disk and sparked a young star, which "grew" to 11 times the weight of the sun in 20,000 simulated years, just as theory predicted. Past that point, things starting getting interesting. First the disc surrounding the star grew spiral arms that helped shovel gas into its maw for another 6,000 years, until it grew to 17 times heftier than our sun.

At that point, the radiation pressure from the star began to out-battle the force of gravity. But instead of pushing the disc gas away evenly, the radiation pressure blew out powerful "bubbles" along the axes of the star. "Almost all gas falling onto the protostar struck the walls of the bubbles, where it was shocked and swept up into the bubble walls. However, this did not slow accretion in our simulation, because the gas that struck the bubble walls eventually traveled along the margin until it reached the disk, at which point it continued to accrete onto the star," reports the study released by the journal Science. "The trick is to look at the star in three dimensions where you see these bubbles develop," Krumholz says.

Avoiding any jokes about Alka-Seltzer, Krumholz and colleagues find the bubbles give the radiation pressure a way to escape, while letting the star continue to gobble up more star-forming stuff. Interestingly, a second stars started to form in the gas disk as the process becomes more unbalanced with the strengthening of the radiation bubbles. Why massive stars always have companions was another mystery, one the simulation thereby also cleared up, a two-fer for astronomy. (A third star actually formed in the simulation, but that unfortunate orb fell back into its parent star.)

After about 57,000 years of simulated time, the researchers halted the star's growth, finding it had quite burgeoned to about 70 times the mass of the sun. "It ran for 40 days and 40 nights, when you add it up," of expensive supercomputer time, Krumholz says.

So that mystery solved, the question of why super-massive stars top off at about 120 times the weight of the sun remains. "The size of a star in our simulation is only limited by the size of the starting gas cloud," Krumholz says. He and others suspect some still-undiscovered mechanism starts knocking out interior explosions of star stuff, like those seen from Eta Carinae, once they reach the most overstuffed sizes, Krumholz says. "You can lose mass in a hurry by spitting out 10-solar-mass eruptions, after all."

Astronomers discover Super-Neptune


This artist's conception reveals the newly discovered super-Neptune planet orbiting a star 120 light years away from Earth. Normally blue in colour, its red hue is caused by the illumination from the nearby red dwarf star. Image: David A. Aguilar (CfA).

Astronomers at the Harvard-Smithsonian Center for Astrophysics have discovered a planet 4.7 times the size of Earth and 25 times more massive, earning it the nickname of a “super-Neptune”.

HAT-P-11b was discovered via the transit method, whereby a planet passes in front of its parent star, thus temporarily, but periodically reducing its brightness as seen by an observer in the same line of sight. In the case of HAT-P-11b, the periodic dimming, which reduced the stars luminosity by around 0.4 percent, was detected by a network of small, automated telescopes known as HATNet, which is operated by the Harvard-Smithsonian Center for Astrophysics in Arizona and Hawaii.

HAT-P-11b is the 11th extrasolar planet found by HATNet, and an important addition to the inventory of exoplanets since it is one of the smallest yet discovered by any of the several transit search projects underway around the world. Compared with our own Solar System’s planet Neptune, which has a diameter 3.8 times that of Earth and a mass 17 times Earth's, the new world is 4.7 times the size of Earth and has 25 Earth masses, placing it into the category of super-Neptunes.

Furthermore, the newfound world orbits very close to its star at a rate of one revolution every 4.88 days. As a result, it is baked to a temperature of around 600 degrees Celsius. The host star, HAT-P-11 is roughly three-quarters the size of our own Sun and somewhat cooler.

The astronomers who made the discovery say that there are indications of a second planet in the HAT-P-11 system, but more radial velocity data are needed to confirm this, and to subsequently determine its properties. The radial velocity technique allows a planet to be inferred by looking at the ‘wobble’ induced on its host star.

A separate team has already located another transiting super-Neptune, known as GJ436b, around a different star, which was discovered by a radial velocity search and later found to have transits. "Having two such objects to compare helps astronomers to test theories of planetary structure and formation," says Harvard astronomer Gaspar Bakos.

The HAT-P-11 system will come under further scrutiny once the forthcoming Kepler mission begins operations. Located in the constellation Cygnus, HAT-P-11 is favourably situated for Kepler to provide the finer details, and maybe even uncover more planets, in this extrasolar planetary system. "We expect Kepler to measure the detailed properties of HAT-P-11 with the extraordinary precision possible only from space," says Robert Noyes, another member of the super-Neptune discovery team.

Kepler is currently scheduled to launch on 6 March this year (2009), and will seek out extrasolar planets using the transit technique. A lot of hopes are riding on this mission, for it has the potential to detect the first Earthlike world orbiting a distant star.

Source: Astronomy Now

NASA-Funded Study Reveals Hazards of Severe Space Weather

01.05.09



The image shows a scenario presented by a study participant of extreme space weather that leads to a partial, wide-spread collapse of the U.S. electric power grid with enormous consequences for the affected population. Improvements in space weather forecasting, public awareness and infrastructure preparedness can mitigate the effects. Credit: NASA A NASA-funded study describes how extreme solar eruptions could have severe consequences for communications, power grids and other technology on Earth.

The National Academy of Sciences in Washington conducted the study. The resulting report provides some of the first clear economic data that effectively quantifies today's risk of extreme conditions in space driven by magnetic activity on the sun and disturbances in the near-Earth environment. Instances of extreme space weather are rare and are categorized with other natural hazards that have a low frequency but high consequences.

"Obviously, the sun is Earth's life blood," said Richard Fisher, director of the Heliophysics division at NASA Headquarters in Washington. "To mitigate possible public safety issues, it is vital that we better understand extreme space weather events caused by the sun's activity."

Besides emitting a continuous stream of plasma called the solar wind, the sun periodically releases billions of tons of matter called coronal mass ejections. These immense clouds of material, when directed toward Earth, can cause large magnetic storms in the magnetosphere and upper atmosphere. Such space weather can affect the performance and reliability of space-borne and ground-based technological systems.

Space weather can produce solar storm electromagnetic fields that induce extreme currents in wires, disrupting power lines, causing wide-spread blackouts and affecting communication cables that support the Internet. Severe space weather also produces solar energetic particles and the dislocation of the Earth's radiation belts, which can damage satellites used for commercial communications, global positioning and weather forecasting. Space weather has been recognized as causing problems with new technology since the invention of the telegraph in the 19th century.



A severe space weather event is likely when an intense flare occurs on the Earth-facing side of the sun. In 2003, this flare (left image) is followed immediately by an enormous interplanetary blast wave (right image) called coronal mass ejection or CME that propagates rapidly away from the sun towards Earth. Depending on severity and nature of the storm, the collision with Earth's magnetic field called a geomagnetic storm can affect satellites, air travel and power grids. Credit: NASA

A catastrophic failure of commercial and government infrastructure in space and on the ground can be mitigated through raising public awareness, improving vulnerable infrastructure and developing advanced forecasting capabilities. Without preventive actions or plans, the trend of increased dependency on modern space-weather sensitive assets could make society more vulnerable in the future.

NASA requested the study to assess the potential damage from significant space weather during the next 20 years. National and international experts from industry, government and academia participated in the study. The report documents the possibility of a space weather event that has societal effects and causes damage similar to natural disasters on Earth.

"From a public policy perspective, it is quite significant that we have begun the extremely challenging task of assessing space weather impacts in a quantitative way," said Daniel Baker, professor and director of the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. Baker chaired the panel that prepared the report.

"Whether it is terrestrial catastrophes or extreme space weather incidents, the results can be devastating to modern societies that depend in a myriad of ways on advanced technological systems," said Baker. "We were delighted that NASA helped support bringing together dozens of world experts from industry and government to share their experiences and begin planning of improved public policy strategies."



The geomagnetic storms' effects can be visualized over the U.S. by showing changes of the electron density in the Earth's outermost atmospheric layers. The before image shows the ionosphere electron density as high over wide parts of the lower 48 states. The after image shows electrons strongly diminished over the central and northeastern parts of the U.S, and increased over the northwest. Extreme, rapid changes in the ionosphere can inflict strong currents in the power grid that may lead to blackouts. Credit: NASA

The sun is currently near the minimum of its 11-year activity cycle. It is expected that solar storms will increase in frequency and intensity toward the next solar maximum, expected to occur around 2012.

The Heliophysics Division of NASA's Science Mission Directorate in Washington provided funding for the study. The division seeks to understand the sun, its solar processes and the interaction of solar plasma and radiation with Earth, other planets and the universe. Understanding the connections between the sun and its planets will allow better prediction on the impacts of solar activity on humans, technological systems and even the presence of life itself in the universe.

The National Academies are chartered by Congress to provide independent technical and scientific advice to the federal government.

Source: NASA

Cassiopeia A Comes Alive Across Time and Space

01.06.09



Cassiopeia A, the supernova remnant that was Chandra's "First Light" image that has been observed ever since.

Two new efforts have taken a famous supernova remnant from the static to the dynamic. A new movie of data from NASA's Chandra X-ray Observatory shows changes in time never seen before in this type of object. A separate team will also release a dramatic three-dimensional visualization of the same remnant.

Nearly ten years ago, Chandra's "First Light" image of Cassiopeia A (Cas A) revealed previously unseen structures and detail. Now, after eight years of observation, scientists have been able to construct a movie that tracks the remnant's expansion and changes over time.

"With Chandra, we have watched Cas A over a relatively small amount of its life, but so far the show has been amazing," said Daniel Patnaude of the Smithsonian Astrophysical Observatory in Cambridge, Mass. "And, we can use this to learn more about the aftermath of the star's explosion."

A separate, but equally fascinating visualization featuring Cas A was presented, along with the Patnaude team's results, at a press conference at the American Astronomical Society meeting in Long Beach, Calif. Based on data from Chandra, NASA's Spitzer Space Telescope, and ground-based optical telescopes, Tracey DeLaney and her colleagues have created the first three-dimensional fly-through of a supernova remnant.

"We have always wanted to know how the pieces we see in two dimensions fit together with each other in real life," said DeLaney of the Massachusetts Institute of Technology. "Now we can see for ourselves with this ‘hologram’ of supernova debris."

This ground-breaking visualization of Cas A was made possible through a collaboration with the Astronomical Medicine project based at Harvard. The goal of this project is to bring together the best techniques from two very different fields, astronomy and medical imaging.

"Right now, we are focusing on improving three-dimensional visualization in both astronomy and medicine," said Harvard’s Alyssa Goodman who heads the Astronomical Medicine project. "This project with Cas A is exactly what we have hoped would come out of it."

While these are stunning visuals, both the data movie from Patnaude and the 3-D model from DeLaney are, more importantly, rich resources for science. The two teams are trying to get a much more complete understanding of how this famous supernova explosion and its remnant work.

Patnaude and his team have measured the expansion velocity of features in Cas A from motions in the movie, and find it is slower than expected based on current theoretical models. Patnaude thinks the explanation for this mysterious loss of energy is cosmic ray acceleration.



Artist concept of supernova remnant Cassiopeia.

Using estimates of the properties of the supernova explosion, including its energy and dynamics, Patnaude's group show that about 30% of the energy in this supernova has gone into accelerating cosmic rays, energetic particles that are generated, in part, by supernova remnants and constantly bombard the Earth's atmosphere. The flickering in the movie provides valuable new information about where the acceleration of these particles occurs.

Likewise, the new 3-D model of Cas A provides researchers with unique ability to study this remnant. With this new tool, Delaney and colleagues found two components to the explosion, a spherical component from the outer layers of the star and a flattened component from the inner layers of the star.

Notable features of the model are high-velocity plumes from this internal material that are shooting out from the explosion. Plumes, or jets, of silicon appear in the northeast and southwest, while plumes of iron are seen in the southeast and north. Astronomers had known about the plumes and jets before, but did not know that they all came out in a broad, disk-like structure.

The implication of this work is that astronomers who build models of supernova explosions must now consider that the outer layers of the star come off spherically, but the inner layers come out more disk like with high-velocity jets in multiple directions.

Cassiopeia A is the remains of a star thought to have exploded about 330 years ago, and is one of the youngest remnants in the Milky Way galaxy. The study of Cas A and remnants like it help astronomers better understand how the explosions that generate them seed interstellar gas with heavy elements, heat it with the energy of their radiation, and trigger shock waves from which new stars form.

Lawrence Rudnick of the University of Minnesota led the Spitzer part of the Delaney study. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Source: NASA

Globular Cluster



Of three objects prominent in this thoughtful telescopic image, a view toward the stealthy constellation Lynx, two (the spiky ones) are nearby stars. The third is the remote globular star cluster NGC 2419, at distance of nearly 300,000 light-years. NGC 2419 is sometimes called "the Intergalactic Wanderer", an appropriate title considering that the distance to the Milky Way's satellite galaxy, the Large Magellanic Cloud, is only about 160,000 light-years. Roughly similar to other large globular star clusters like Omega Centauri, NGC 2419 is itself intrinsically bright, but appears faint because it is so far away. NGC 2419 may really have an extragalactic origin as, for example, the remains of a small galaxy captured and disrupted by the Milky Way. But its extreme distance makes it difficult to study and compare its properties with other globular clusters that roam the halo of our Milky Way galaxy.

Largest Full Moon of 2009



A larger moon will not be seen this year. This past weekend, the largest full Moon of 2009 could be seen from almost any clear location on planet Earth at night. The large angular extent of the full Moon was caused by the Moon being unusually close to Earth during its full phase. Because the Moon circles the Earth in an elliptical orbit, its angular size depends on how close the Moon is to closest approach (perigee) or farthest distance (apogee). Even so, the Moon's was only about 15 percent larger in area and brightness than a more typical full Moon. In this image, a dramatically positioned Moon is seen rising above the Alps from Breil-sur-Roya in the southeast of France. Taken with an ordinary digital camera but extraordinary timing, the image also captured a crossing jet plane. The last full Moon, in 2008 December, was the largest full moon of 2008.

Planetary Nebula



NGC 2818 is a beautiful planetary nebula, the gaseous shroud of a dying sun-like star. It could well offer a glimpse of the future that awaits our own Sun after spending another 5 billion years or so steadily using up hydrogen at its core, and then finally helium, as fuel for nuclear fusion. Curiously, NGC 2818 seems to lie within a sparse open star cluster, NGC 2818A, that is some 10,000 light-years distant toward the southern constellation Pyxis (Compass). Since open star clusters disperse after only a few hundred million years, this one must be exceptionally old to have one of its member stars evolve to the planetary nebula stage. At the distance of the star cluster, planetary nebula NGC 2818 would be about 4 light-years across. The Hubble image is a composite of exposures through narrow-band filters, presenting emission from nitrogen, hydrogen, and oxygen atoms in the nebula as red, green, and blue hues.

Indonesians among the few to witness solar eclipse


The moon cast a shadow at the sun blocking it partially in a partial solar eclipse as it sets on
Monday Jan. 26, 2009 at Manila's bay, Philippines. (AP Photo/Aaron Favila)

ANYER, Indonesia—Indonesians were among the few worldwide to witness an eclipse of the sun Monday, some cheering and banging on drums as the moon slowly crossed its path, blocking out everything but a thin, blazing rim of fire.

Dozens gathered in the western coastal town of Anyer to see the spectacle, which peaked at 4:40 p.m. and lasted for about four minutes.

"I'm old, but I still think this is magical," said Roanna Makmur, 66, who drove several hours with eight friends to witness the sight, known as an annular eclipse, because it does not completely black out the sun.

"I can't help but feel the greatness of God," she said, as fellow onlookers applauded and then fell silent. "Anyone who passed up this opportunity, really missed out."

Annular eclipses, which are considered far less important to astronomers than total eclipses of the sun, occur about 66 times a century and can only be viewed by people in the narrow band along its path.

Aside from several regions in Indonesia -- from Sumatra island in the west to Kalimantan in the east -- only villagers on a tiny South Pacific island group known as the Cocos could see Monday's eclipse, said Jay Pasachoff, professor of astronomy at Williams College in Williamstown, Massachusetts. He is also a chair of the International Astronomical Union's Working Group on Eclipses.

But a partial eclipse -- with coverage ranging from 1 percent to 84 percent of the sun's diameter -- was to visible in the southern third of Africa, in southeastern India, and Southeast Asia, as well as the western part of Australia.

Hundreds turned out in Indonesia's Samarinda, the capital of East Kalimantan province, where more than 90 percent of the sun's diameter was covered. Some ignored danger warnings and looked directly at the sun. Others wore sunglasses to protect their eyes or looked at its reflection in buckets of water.

"We are so happy we were able to see this," said Fauziah Sulaiman, a mother of two, who was standing outside her house. "It's great for the children, especially after learning about it in school."

The last total eclipse of the sun was Aug. 1, 2008, and was visible in Canada, across northern Greenland, the Arctic, central Russia, Mongolia and China.

The next total eclipse will be July 22, 2009, and will be visible in India, Nepal, Bangladesh, Bhutan, Myanmar, China and some Japanese islands.

Source

Scientists Peek Inside Dark Moon Craters

Jan. 16) - Using a NASA radar flying aboard India's Chandrayaan-1 spacecraft, scientists are getting their first look inside the moon's coldest, darkest craters, where some suspect ice may be hiding.

The Mini-SAR instrument, a lightweight, synthetic aperture radar, has passed its initial in-flight tests and sent back its first data. The images show the floors of permanently-shadowed polar craters on the moon that aren't visible from Earth.

Scientists are using the instrument to map and search the insides of the craters for water ice.
"The only way to explore such areas is to use an orbital imaging radar such as Mini-SAR," said Benjamin Bussey, deputy principal investigator for Mini-SAR, from the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "This is an exciting first step for the team which has worked diligently for more than three years to get to this point."


This image shows a part of the moon never seen before: a portion of Haworth crater that is permanently shadowed from Earth and the sun. Some scientists suspect ice may be hiding deep inside the region. The image was captured by Mini-SAR radar aboard India's Chandrayaan-1 spacecraft. It was released Jan. 14.


The images, taken on Nov. 17, 2008, cover part of the Haworth crater at the moon's south pole and the western rim of Seares crater, an impact feature near the north pole. Bright areas in each image represent either surface roughness or slopes pointing toward the spacecraft.

Further data collection by Mini-SAR and analysis will help scientists to determine if buried ice deposits exist in the permanently shadowed craters near the moon's poles.
"During the next few months we expect to have a fully calibrated and operational instrument collecting valuable science data at the moon," said Jason Crusan, program executive for the Mini-RF Program for NASA's Space Operations Mission Directorate in Washington.
Mini-SAR is one of 11 instruments on the Indian Space Research Organization's Chandrayaan-1 and one of two NASA-sponsored contributions to its international payload. The other is the Moon Mineralogy Mapper, a state-of-the-art imaging spectrometer that willvprovide the first map of the entire lunar surface at high spatial and spectral resolution.
Chandrayaan-1 launched from India's Satish Dhawan Space Center on Oct. 21 and began orbiting the moon Nov. 8.

Source

First glimpse of X-ray from the Moon

The C1XS X-ray camera will build up a detailed picture of the ingredients that have gone into the Moon.
Provided by the STFC, United Kingdom

January 23, 2009
The C1XS X-ray camera on the Chandrayaan-1 spacecraft orbiting the Moon successfully detected its first Xray signature from the Moon. This is the first step in its mission to reveal the origin and evolution of our Moon by mapping its surface composition.

jointly developed by the United Kingdom's Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory and the Indian Space Research Organization (ISRO), has successfully detected its first X-ray signature from the Moon. This is the first step in its mission to reveal the origin and evolution of our Moon by mapping its surface composition.

C1XS, jointly developed by the United Kingdom's Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory and the Indian Space Research Organization (ISRO, detected the X-ray signal from a region near the Apollo landing sites December 12, 2008, at 02:36 Universal Time. The solar flare that caused the X-ray fluorescence was exceedingly weak, approximately 20 times smaller than the minimum C1XS was designed to detect.

"C1XS has exceeded expectations as to its sensitivity and has proven that it is the most sensitive X-ray spectrometer of its kind in history," said Shyama Narendranath, Instrument Operations Scientist at ISRO.

The X-ray camera collected 3 minutes of data from the Moon just as the flare started and the camera finished its observation. The signal reveals the X-ray fingerprint of a part of the lunar surface. As the mission continues, C1XS will build up a detailed picture of the ingredients that have gone into the Moon.

Barry Kellett, instrument scientist from STFC's Space Science and Technology Department said, "Despite the small quantity of data, our initial analysis and modeling shows that C1XS has identified the chemistry of this area of the Moon".

Professor Manuel Grande, principal investigator, Aberystwyth University in Wales, concluded, "The quality of the flare signal detected from the Moon clearly demonstrates that C1XS is in excellent condition and has survived the passage of Chandrayaan-1 through Earth's radiation (or van Allen) belts with very little damage. This is excellent news for the rest of the Chandrayaan-1 mission".


The Full Moon. Gregory Terrance

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Space Mission For Worms

ScienceDaily (Jan. 20, 2009) — Worms from The University of Nottingham should be checking in for a flight onboard the Space Shuttle later this year — to help researchers investigate the effect of zero gravity on the body’s muscle development and physiology. Researchers are also hoping to get primary school children involved in the project.

The worms will spend about two weeks in the Japanese Kibo laboratory onboard the International Space Station (ISS) before returning to earth.

Dr Nathaniel Szewczyk, from the Institute of Clinical Research in Derby, studies the signals that control muscle protein degradation and is an old hand at organising space travel for worms to do this. The 2009 mission will be his fourth space worm project — his booking on the ISS has been negotiated through the Japanese space agency. The worms are scheduled to fly to the ISS onboard the Space Shuttle Discovery as part of NASA’s mission STS-129/ULF-3, currently scheduled for October.

Dr Szewczyk’s work centres on the microscopic worm, Caenorhabditis elegans (C. elegans). These worms are the perfect substitute for studying long term changes in human physiology because they suffer from muscle atrophy — muscle loss — under many of the same conditions that people do.

The worms are being sent into space to understand more about muscle atrophy in the hope of helping people who suffer from muscle wasting which can be caused by a myriad of diseases and conditions. Dr Szewczyk wants to explain why astronauts can experience dramatic muscle loss — some astronauts can lose up to 60 per cent of their muscle density in a single mission.

Dr Szewczyk said: “Worms are an excellent model to study the genetic basis of muscle atrophy. This flight should allow us to continue to uncover new ways muscle atrophy is controlled. Our current results suggest that our findings from this space flight mission may be of particular interest not only to astronauts but also to individuals who are bed ridden, immobilized in casts, aged, or who suffer diabetes.”

The C. elegans was the first multi-cellular organism to have its genetic structure completely mapped and many of its 20,000 genes perform the same functions as those in humans. Two thousand of these genes have a role in promoting muscle function and 50 to 60 per cent of these have very obvious human counterparts.

The experiment will be part of the Japanese CERISE payload and is being funded as part of a $1M (£0.6M) United States National Institute of Health grant to investigate the genetic basis of muscle atrophy. The recently installed Kibo lab is being used for the study of biomedicine and material sciences making use of the weightless conditions experienced in orbit.

Biological experiments in space need life support — oxygen, temperature control and pressure — so competition for space on manned flights is fierce and in short supply. The selection process is decided on an international basis through the International Life Sciences working group.

The origins of Dr Szewczyk’s worms can be traced back to a rubbish dump in Bristol. C. elegans often feed on bacteria that develop on decaying vegetable matter. In space they will be fed bacteria that have been heat inactivated.

Dr Szewczyk’s C. elegans made news in 2003 when they survived the Space Shuttle Columbia disaster. Living in petri dishes and enclosed in aluminium canisters the worms survived re-entry and impact on the ground and were recovered weeks after the disaster.

Space flight research poses two big problems — access and money. Securing a place onboard the international space station is not only expensive it is also an exercise in diplomacy and international politics. It might not come up with as many direct answers as research carried out on Earth but Dr Szewczyk argues that space flight research is a unique opportunity to put life in difficult conditions and learn something fundamental about it. He also thinks that the work is a great way to get school children excited about science. He plans to work with Orion’s quest to involve primary school children in this experiment.

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Jodrell Bank Links with Other Observatories to Create Radio Telescope the Size of Earth
Posted by Guy Pirro on 1/25/2009 7:57 PM


The image shows the University of Manchester's giant Lovell Telescope at the Jodrell Bank Observatory in the UK. Telescopes around the world participated in this real-time experiment, including several from separate organizations that run their own VLBI-networks (for example the Long Baseline Array (LBA) in Australia, the Very Long Baseline Array (VLBA) in North-America, and the European VLBI Network (EVN) in Europe). Radiotelescopes on all the continents were used to observe continuously. The target was always above the horizon for some of the telescopes. As the earth turned on its axis, the target became visible for some telescopes and disappeared below the horizon for others. The dataflow from telescopes was started and stopped accordingly and the data was collected and correlated at a central point in real-time. These facilities provided scientists with the highest resolution astronomical images available to date. (Image Credit: Anthony Holloway, Jodrell Bank)

Radio telescopes around the world joined forces last week to carry out a unique observation of three quasars -- distant galaxies powered by super-massive black holes at their cores. The nearly continuous 33-hour observation was conducted by seventeen telescopes in Asia, Australia, Europe, North America, and South America, including several operated from the University of Manchester's Jodrell Bank Observatory.

Arpad Szomoru, Head of Technical Operations and R&D at the Joint Institute for VLBI in Europe (JIVE) noted, "The unique aspect of these observations is that telescopes located all around the globe will be brought together to work in real-time as a single gigantic instrument."

Using an astronomical technique called electronic, real-time Very Long Baseline Interferometry (e-VLBI), participating telescopes observed the same object simultaneously. Data from each telescope was streamed across the globe through high-speed optical networks to a purpose-built supercomputer called a correlator located at JIVE in the Netherlands. This machine acted as the focus of the giant distributed telescope, the largest real-time telescope ever, combining the signals collected from instruments across the world.

"By combining information from such widely separated radio telescopes we can produce incredibly sharp images with up to one hundred times better resolution than those available from the best optical telescopes", said Simon Garrington, Director of the UK's MERLIN/VLBI National Facility. "It's like being able to sit here in Manchester and read a newspaper in London".

“It was almost a feeling like the Olympic torch being passed around the world,” said Garrington.

With e-VLBI the ability to send data electronically and combine it in real-time has the additional advantage of providing results to astronomers within hours of conducting an observation, rather than weeks later via the traditional VLBI method of recording data onto disks and shipping it to the correlator.

JIVE Director Huib Jan van Langevelde explained, "With VLBI we can zoom in on the most energetic events in the universe, and the new e-VLBI technique allows us to do this fast enough to catch such events on the time-scale that they occur and respond quickly."

This e-VLBI observation was made possible by the Express Production Real-time e-VLBI Service (EXPReS). Funded by the European Commission, EXPReS has been working since 2006 to connect radio telescopes around the world to the correlator at JIVE using high-speed optical networks.

Source

Milky Way a Swifter Spinner, More Massive, New Measurements Show
Posted by Paul Walsh on 1/5/2009


Image Credit: Harvard-Smithsonian Center for Astrophysics

Long Beach, CA - Fasten your seat belts -- we're faster, heavier, and more likely to collide than we thought. Astronomers making high-precision measurements of the Milky Way say our Galaxy is rotating about 100,000 miles per hour faster than previously understood.

That increase in speed, said Mark Reid of the Harvard-Smithsonian Center for Astrophysics, increases the Milky Way's mass by 50 percent, bringing it even with the Andromeda Galaxy. "No longer will we think of the Milky Way as the little sister of the Andromeda Galaxy in our Local Group family."

The larger mass, in turn, means a greater gravitational pull that increases the likelihood of collisions with the Andromeda galaxy or smaller nearby galaxies.

Our solar system is about 28,000 light-years from the Milky Way’s center. At that distance, the new observations indicate, we’re moving at about 600,000 miles per hour in our Galactic orbit, up from the previous estimate of 500,000 miles per hour.

The scientists are using the National Science Foundation’s Very Long Baseline Array (VLBA) radio telescope to remake the map of the Milky Way. Taking advantage of the VLBA’s unparalleled ability to make extremely detailed images, the team is conducting a long-term program to measure distances and motions in our Galaxy. They reported their results at the American Astronomical Society’s meeting in Long Beach, California.

The scientists observed regions of prolific star formation across the Galaxy. In areas within these regions, gas molecules are strengthening naturally-occurring radio emission in the same way that lasers strengthen light beams. These areas, called cosmic masers, serve as bright landmarks for the sharp radio vision of the VLBA. By observing these regions repeatedly at times when the Earth is at opposite sides of its orbit around the Sun, the astronomers can measure the slight apparent shift of the object’s position against the background of more distant objects.

“The new VLBA observations of the Milky Way are producing highly-accurate direct measurements of distances and motions,” said Karl Menten of the Max Planck Institute for Radio Astronomy in Germany, a member of the team. “These measurements use the traditional surveyor’s method of triangulation and do not depend on any assumptions based on other properties, such as brightness, unlike earlier studies.”

The astronomers found that their direct distance measurements differed from earlier, indirect measurements, sometimes by as much as a factor of two. The star-forming regions harboring the cosmic masers “define the spiral arms of the Galaxy,” Reid explained. Measuring the distances to these regions thus provides a yardstick for mapping the Galaxy’s spiral structure.

“These direct measurements are revising our understanding of the structure and motions of our Galaxy,” Menten said. "Because we’re inside it, it’s difficult for us to determine the Milky Way’s structure. For other galaxies, we can simply look at them and see their structure, but we can’t do this to get an overall image of the Milky Way. We have to deduce its structure by measuring and mapping,” he added.

The VLBA can fix positions in the sky so accurately that the actual motion of the objects can be detected as they orbit the Milky Way’s center. Adding in measurements of motion along the line of sight, determined from shifts in the frequency of the masers’ radio emission, the astronomers are able to determine the full 3-dimensional motions of the star-forming regions. Using this information, Reid reported that “most star-forming regions do not follow a circular path as they orbit the Galaxy; instead we find them moving more slowly than other regions and on elliptical, not circular, orbits.”

The researchers attribute this to what they call spiral density-wave shocks, which can take gas in a circular orbit, compress it to form stars, and cause it to go into a new, elliptical orbit. This, they explained, helps to reinforce the spiral structure.

Reid and his colleagues found other surprises, too. Measuring the distances to multiple regions in a single spiral arm allowed them to calculate the angle of the arm. “These measurements,” Reid said, “indicate that our Galaxy probably has four, not two, spiral arms of gas and dust that are forming stars.” Recent surveys by NASA’s Spitzer Space Telescope suggest that older stars reside mostly in two spiral arms, raising a question of why the older stars don't appear in all the arms. Answering that question, the astronomers say, will require more measurements and a deeper understanding of how the Galaxy works.

The VLBA, a system of 10 radio-telescope antennas stretching from Hawaii to New England and the Caribbean, provides the best ability to see the finest detail, called resolving power, of any astronomical tool in the world. The VLBA can routinely produce images hundreds of times more detailed than those produced by the Hubble Space Telescope. The VLBA’s tremendous resolving power, equal to being able to read a newspaper in Los Angeles from the distance of New York, is what permits the astronomers to make precise distance determinations.

This release was issued jointly with the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Article Credit: Harvard-Smithsonian Center for Astrophysics

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THEMIS Explorers Discover Giant Breach in Earth's Magnetic Field
Posted by Guy Pirro on 1/11/2009 7:37 PM


This is an artist's concept of the THEMIS main orbits, represented by red ovals. Blue lines represent the Earth's magnetic field. The white flash represents energy released during substorms. The THEMIS spacecraft will line up at midnight over the United States every four days. The distances range from about half the distance to the moon to about sixth of the distance to the moon. This position will help scientists pinpoint exactly when and where substorms occur. (Image Credit: NASA)

NASA's five THEMIS spacecraft have discovered a breach in Earth's magnetic field ten times larger than anything previously thought to exist. Solar wind can flow in through the opening to "load up" the magnetosphere for powerful geomagnetic storms. But the breach itself is not the biggest surprise. Researchers are even more amazed at the strange and unexpected way it forms, overturning long-held ideas of space physics.

"At first I didn't believe it," says THEMIS project scientist David Sibeck of the Goddard Space Flight Center. "This finding fundamentally alters our understanding of the solar wind-magnetosphere interaction."

The magnetosphere is a bubble of magnetism that surrounds Earth and protects us from solar wind. Exploring the bubble is a key goal of the THEMIS mission, launched in February 2007. The big discovery came on June 3, 2007, when the five probes serendipitously flew through the breach just as it was opening. Onboard sensors recorded a torrent of solar wind particles streaming into the magnetosphere, signaling an event of unexpected size and importance.

"The opening was huge—four times wider than Earth itself," says Wenhui Li, a space physicist at the University of New Hampshire who has been analyzing the data. Li's colleague Jimmy Raeder, also of New Hampshire, says "1027 particles per second were flowing into the magnetosphere—that's a 1 followed by 27 zeros. This kind of influx is an order of magnitude greater than what we thought was possible."

The event began with little warning when a gentle gust of solar wind delivered a bundle of magnetic fields from the Sun to Earth. Like an octopus wrapping its tentacles around a big clam, solar magnetic fields draped themselves around the magnetosphere and cracked it open. The cracking was accomplished by means of a process called "magnetic reconnection." High above Earth's poles, solar and terrestrial magnetic fields linked up (reconnected) to form conduits for solar wind. Conduits over the Arctic and Antarctic quickly expanded; within minutes they overlapped over Earth's equator to create the biggest magnetic breach ever recorded by Earth-orbiting spacecraft.

The size of the breach took researchers by surprise. "We've seen things like this before," says Raeder, "but never on such a large scale. The entire day-side of the magnetosphere was open to the solar wind."

The circumstances were even more surprising. Space physicists have long believed that holes in Earth's magnetosphere open only in response to solar magnetic fields that point south. The great breach of June 2007, however, opened in response to a solar magnetic field that pointed north.

"To the lay person, this may sound like a quibble, but to a space physicist, it is almost seismic," says Sibeck. "When I tell my colleagues, most react with skepticism, as if I'm trying to convince them that the sun rises in the west."

Here is why they can't believe their ears: The solar wind presses against Earth's magnetosphere almost directly above the equator where our planet's magnetic field points north. Suppose a bundle of solar magnetism comes along, and it points north, too. The two fields should reinforce one another, strengthening Earth's magnetic defenses and slamming the door shut on the solar wind. In the language of space physics, a north-pointing solar magnetic field is called a "northern IMF" and it is synonymous with shields up!

"So, you can imagine our surprise when a northern IMF came along and shields went down instead," says Sibeck. "This completely overturns our understanding of things."

Northern IMF events don't actually trigger geomagnetic storms, notes Raeder, but they do set the stage for storms by loading the magnetosphere with plasma. A loaded magnetosphere is primed for auroras, power outages, and other disturbances that can result when, say, a CME (coronal mass ejection) hits.

The years ahead could be especially lively. Raeder explains: "We're entering Solar Cycle 24. For reasons not fully understood, CMEs in even-numbered solar cycles (like 24) tend to hit Earth with a leading edge that is magnetized north. Such a CME should open a breach and load the magnetosphere with plasma just before the storm gets underway. It's the perfect sequence for a really big event."

Sibeck agrees. "This could result in stronger geomagnetic storms than we have seen in many years."

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Russia Downplays Danger of Leaking Nuclear Satellite
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SPACE.com Space News Staff

space.com – Mon Jan 26, 6:16 pm ETRussia's Space Forces minimized the risk posed by a long-retired nuclear-powered satellite that the U.S. Space Surveillance Network (SSN) identified as producing "an unexpected debris cloud" in July.


In statements released Jan. 21, the Space Forces said the Cosmos 1818 satellite, orbiting at 800 kilometers, is not a danger to other satellites in that orbit and will disintegrate when it reenters the Earth's atmosphere sometime in the middle of this century.


A NASA analysis of SSN data found that Cosmos 1818, launched in February 1987, was the source of a "fragmentation event" around July 4 that released at least 30 small pieces of debris.


In its Orbital Debris Quarterly News report issued Jan. 15, NASA's Orbital Debris Program Office says the debris could be droplets of sodium-potassium, which was used as a coolant for the satellite's nuclear power generator. Direct exposure to the sun could have warmed the coolant to a liquid state. NASA said the released objects resemble metallic spheres.


A satellite featuring a similar design, called Cosmos 1867, has not released any similar debris up to now, NASA said.


The NASA analysis said Cosmos 1818 and 1867 were test satellites to demonstrate a new kind of nuclear power in low Earth orbit, but at an altitude much higher than the 250-kilometer operating orbit of Russia's Rorsat ocean-reconnaissance satellites. A Rorsat satellite failed in orbit in 1978, breaking up in the atmosphere and causing radioactive debris to fall over Canada.


The NASA report said that two years after China used a ground-based missile to destroy the retired Chinese Fengyun-1C weather satellite in an 800-kilometer orbit, SSN is tracking nearly 2,800 pieces of debris measuring at least 5 centimeters in diameter. "The estimated population of debris larger than 1 centimeter is greater than 150,000," NASA said. "The Fengyun-1C debris cloud easily constitutes the largest collection of fragments in Earth orbit."

NASA camera gets unique inaugural image
WASHINGTON (UPI) -- The U.S. space agency says one of its spinoff technologies from the Mars rovers was used to capture a unique image of President Barack Obama's inauguration.

The National Aeronautics and Space Administration said photographer David Bergman used the Gigapan camera system to generate an image that's a combination of 220 images with an overall size of 1,474 megapixels.

"The Gigapan system is a NASA spinoff technology that can capture thousands of digital images and weave them into a uniform high-resolution picture of more than a billion pixels," the space agency said.

The technology is the product of a two-year collaboration between NASA and Carnegie Mellon University. The Mars rovers Spirit and Opportunity have used the Gigapan system to explore the Red Planet for more than five years.

The image is extremely detailed and can be easily searched and magnified using on-screen tools. It is available at gigapan: President Barack Obama's Inaugural Address by David Bergman.

NASA's Fermi Gamma-Ray Telescope Unveils a Dozen New Pulsars
A pulsar is a rapidly spinning and highly magnetized neutron star, the crushed core left behind when a massive sun explodes. Most were found through their pulses at radio wavelengths, which are thought to be caused by narrow, lighthouse-like beams emanating from the star's magnetic poles.

If the magnetic poles and the star's spin axis don't align exactly, the spinning pulsar sweeps the beams across the sky. Radio telescopes on Earth detect a signal if one of those beams happens to swing our way. Unfortunately, any census of pulsars is automatically biased because we only see those whose beams sweep past Earth.

"That has colored our understanding of neutron stars for 40 years," Romani says. The radio beams are easy to detect, but they represent only a few parts per million of a pulsar's total power. Its gamma rays, on the other hand, account for 10 percent or more. "For the first time, Fermi is giving us an independent look at what heavy stars do," he adds.

Pulsars are phenomenal cosmic dynamos. Through processes not fully understood, a pulsar's intense electric and magnetic fields and rapid spin accelerate particles to speeds near that of light. Gamma rays let astronomers glimpse the particle accelerator's heart.

"We used to think the gamma rays emerged near the neutron star's surface from the polar cap, where the radio beams form," says Alice Harding of NASA's Goddard Space Flight Center in Greenbelt, Md. "The new gamma-ray-only pulsars put that idea to rest." She and Romani spoke today at the American Astronomical Society meeting in Long Beach, Calif.

Astronomers now believe the pulsed gamma rays arise far above the neutron star. Particles produce gamma rays as they accelerate along arcs of open magnetic field. For the Vela pulsar, the brightest persistent gamma-ray source in the sky, the emission region is thought to lie about 300 miles from the star, which is only 20 miles across.

Existing models place the gamma-ray emission along the boundary between open and closed magnetic field lines. One version starts at high altitudes; the other implies emission from the star's surface all the way out. "So far, Fermi observations to date cannot distinguish which of these models is correct," Harding says.

Because rotation powers their emissions, isolated pulsars slow as they age. The 10,000-year-old CTA 1 pulsar, which the Fermi team announced in October, slows by about a second every 87,000 years.

Fermi also picked up pulsed gamma rays from seven millisecond pulsars, so called because they spin between 100 and 1,000 times a second. Far older than pulsars like Vela and CTA 1, these seemingly paradoxical objects get to break the rules by residing in binary systems containing a normal star. Stellar matter accreted from the companion can spin up the pulsar until its surface moves at an appreciable fraction of light speed.source

Night sky puts on great show
Galileo first turned his telescope to the heavens in 1609. Through years of observations, particularly of Venus’ movements, he later confirmed calculations by Copernicus and others that the planets orbit the sun.
Published: Saturday, January 31, 2009 4:12 AM EST
Galileo first turned his telescope to the heavens in 1609. Through years of observations, particularly of Venus’ movements, he later confirmed calculations by Copernicus and others that the planets orbit the sun.

In observance of the 400th anniversary of Galileo’s first look into the cosmos, the United Nations Educational, Scientific and Cultural Organization and the International Astronomical Union have declared 2009 the International Year of Astronomy.

Beyond the anniversary, there is no better time to celebrate modern astronomy, which is experiencing a truly golden age.

Vast increases in technology over the last few decades have enabled modern astronomers to exponentially expand what is known about the scope of the universe and how it works — and to understand that there is much more to learn.

The age-old questions of whether planets exist beyond Earth’s solar system has been answered, for example, and emphatically.

Astronomers have confirmed the existence of 335 planets orbiting 284 stars, and even have been able to directly observe a few of them using extraordinary instruments such as the Hubble and Spitzer space telescopes.

Here on Earth, governments and universities around the world are collaborating on construction of the largest and most powerful land-based telescopes in history.

In France and Switzerland, the world’s largest superconducting supercollider soon will be powered up to seek the secrets of matter.

And out in the solar system, ingenious devices such as the Cassini spacecraft, which has revealed mountains of information about Saturn and its system, and the fleet of craft orbiting and on the surface of Mars, have markedly increased knowledge about our near cosmic neighborhood.

Around the world, 135 countries are participating in the International Year of Astronomy, itself a tribute to astronomy as a unifying force on this planet.

Initiatives include programs to get as many people as possible to take a look through a telescope, efforts to limit light pollution that inhibits Earth-based observations, and a host of events at planetariums, observatories, universities and among amateur astronomy groups.

The nighttime sky, as Galileo knew 400 years ago, is the greatest show in, well, the universe. More information on how to learn about and appreciate it is at International Year of Astronomy 2009.

Copyright © 2009 - The Republican & Herald

SOURCE

Saturn's Dynamic Moon Enceladus Shows More Signs of Activity

These updated maps of Saturn's moon Titan, consisting of data from the Cassini imaging science subsystem, include Cassini's August 2008 imaging of the moon's northern hemisphere.

Evidence from Cassini's imaging science subsystem, radar, and visual and infrared mapping spectrometer instruments strongly suggests that dark areas near the poles are lakes of liquid hydrocarbons-an analysis affirmed by images capturing those changes in the lakes thought to be brought on by rainfall.

Colored lines in the polar portions of these maps illustrate the boundaries between surface regions having different albedos -- or differences in surface brightness -- which Cassini scientists have interpreted as potential shorelines. Blue outlines indicate features that changed between observations made one year apart (see PIA11147).

The top map is a simple cylindrical projection. Atmospheric effects complicate incorporation of data from high northern latitudes, which are shown separately in a polar view. The map at bottom left is a north polar projection showing latitudes 55 degrees to 90 degrees. The bottom right map is a south polar projection showing latitudes minus55 degrees to minus90 degrees.

The maps are compiled from images dating from April 2004 through August 2008, and their resolutions vary from a few meters to a few tens of kilometers per pixel. Brightness variations are due to differences in surface albedo rather than topographic shading.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit Cassini Equinox Mission . The Cassini imaging team homepage is at .
Credit: NASA/JPL/Space Science Institute

Source
Posted 01/29/09

NASA Study Links Severe Storm Increases, Global Warming

12.19.08



Extremely high clouds, known as deep convective clouds, are typically associated with severe storms and rainfall. In this AIRS image of Hurricane Katrina, taken August 28, 2005, the day before Katrina made landfall in Louisiana, the eye of the storm was surrounded by a "super cluster" of 528 deep convective clouds (depicted in dark blue). The temperatures of the tops of such clouds are colder than 210 degrees Kelvin (-82 degrees Fahrenheit).


PASADENA, Calif. -- The frequency of extremely high clouds in Earth's tropics -- the type associated with severe storms and rainfall -- is increasing as a result of global warming, according to a study by scientists at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

In a presentation today to the fall meeting of the American Geophysical Union in San Francisco, JPL Senior Research Scientist Hartmut Aumann outlined the results of a study based on five years of data from the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua spacecraft. The AIRS data were used to observe certain types of tropical clouds linked with severe storms, torrential rain and hail. The instrument typically detects about 6,000 of these clouds each day. Aumann and his team found a strong correlation between the frequency of these clouds and seasonal variations in the average sea surface temperature of the tropical oceans.

For every degree Centigrade (1.8 degrees Fahrenheit) increase in average ocean surface temperature, the team observed a 45-percent increase in the frequency of the very high clouds. At the present rate of global warming of 0.13 degrees Celsius (0.23 degrees Fahrenheit) per decade, the team inferred the frequency of these storms can be expected to increase by six percent per decade.

Climate modelers have long speculated that the frequency and intensity of severe storms may or may not increase with global warming. Aumann said results of the study will help improve their models.

"Clouds and rain have been the weakest link in climate prediction," said Aumann. "The interaction between the daytime warming of the sea surface under clear-sky conditions and increases in the formation of low clouds, high clouds and, ultimately, rain is very complicated. The high clouds in our observations?typically at altitudes of 20 kilometers (12 miles) and higher?present the greatest difficulties for current climate models, which aren't able to resolve cloud structures smaller than about 250 kilometers (155 miles) in size."

Aumann said the results of his study, published recently in Geophysical Research Letters, are consistent with another NASA-funded study by Frank Wentz and colleagues in 2005. That study found an increase in the global rain rate of 1.5 percent per decade over 18 years, a value that is about five times higher than the value estimated by climate models that were used in the 2007 report of the Intergovernmental Panel on Climate Change.

Source: NASA

Star Light, Star Bright, Its Explanation is Out of Sight

01.06.09



A mysterious flash of light from somewhere near or far in the universe is still keeping astronomers in the dark long after it was first detected by NASA’s Hubble Space Telescope in 2006. It might represent an entirely new class of stellar phenomena, say researchers.

Astronomers commonly observe intense flashes of light from a variety of stellar explosions and outbursts, such as novae and supernovae. Hubble discovered the cosmic flash on February 26, 2006. It steadily rose in brightness for 100 days, and then dimmed back to oblivion after another 100 days.

The rise and fall in brightness has a signature that simply has never been recorded for any other type of celestial event. Supernovae peak after no more than 70 days, and gravitational lensing events are much shorter. Therefore, this observation defies a simple explanation, reports Kyle Barbary of the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, Calif. He is describing the bizarre Hubble observation at the 213th meeting of the American Astronomical Society in Long Beach, Calif. “We have never seen anything like it,” he concludes.

The spectral fingerprints of light coming from the object, cataloged as SCP 06F6, also have eluded identification as being due to any specific element. One guess is that the features are redshifted molecular carbon absorption lines in a star roughly one billion light-years away.

But searches through various astronomical survey catalogs for the source of the light have not uncovered any evidence for a star or galaxy at the location of the flash. The Supernova Cosmology Project at LBNL discovered it serendipitously in a search for supernovae.

Hubble was aimed at a cluster of galaxies 8 billion light-years away in the spring constellation Bootes. But the mystery object could be anywhere in between, even in the halo of our own Milky Way galaxy.

Papers published by other researchers since the event was reported in June 2006, have suggested a bizarre zoo of possibilities: the core collapse and explosion of a carbon rich star, a collision between a white dwarf and an asteroid, or the collision of a white dwarf with a black hole.

But Barbary does not believe that any model offered so far fully explains the observations. “I don’t think we really know what the discovery means until we can observe similar objects in the future.”

All-sky surveys for variable phenomena, such as those to be conducted with the planned Large Synoptic Survey Telescope, may ultimately find similar transient events in the universe.

Source: NASA

The Cat's Eye Nebula: Dying Star Creates Fantasy-like Sculpture of Gas and Dust

In this detailed view from NASA's Hubble Space Telescope, the so-called Cat's Eye Nebula looks like the penetrating eye of the disembodied sorcerer Sauron from the film adaptation of "The Lord of the Rings."

The nebula, formally cataloged NGC 6543, is every bit as inscrutable as the J.R.R. Tolkien phantom character. Though the Cat's Eye Nebula was one of the first planetary nebulae to be discovered, it is one of the most complex such nebulae seen in space. A planetary nebula forms when Sun-like stars gently eject their outer gaseous layers that form bright nebulae with amazing and confounding shapes.

In 1994, Hubble first revealed NGC 6543's surprisingly intricate structures, including concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas.

As if the Cat's Eye itself isn't spectacular enough, this new image taken with Hubble's Advanced Camera for Surveys (ACS) reveals the full beauty of a bull's eye pattern of eleven or even more concentric rings, or shells, around the Cat's Eye. Each 'ring' is actually the edge of a spherical bubble seen projected onto the sky — that's why it appears bright along its outer edge.

Observations suggest the star ejected its mass in a series of pulses at 1,500-year intervals. These convulsions created dust shells, each of which contain as much mass as all of the planets in our solar system combined (still only one percent of the Sun's mass). These concentric shells make a layered, onion-skin structure around the dying star. The view from Hubble is like seeing an onion cut in half, where each skin layer is discernible.

Until recently, it was thought that such shells around planetary nebulae were a rare phenomenon. However, Romano Corradi (Isaac Newton Group of Telescopes, Spain) and collaborators, in a paper published in the European journal Astronomy and Astrophysics in April 2004, have instead shown that the formation of these rings is likely to be the rule rather than the exception.

The bull's-eye patterns seen around planetary nebulae come as a surprise to astronomers because they had no expectation that episodes of mass loss at the end of stellar lives would repeat every 1,500 years. Several explanations have been proposed, including cycles of magnetic activity somewhat similar to our own Sun's sunspot cycle, the action of companion stars orbiting around the dying star, and stellar pulsations. Another school of thought is that the material is ejected smoothly from the star, and the rings are created later on due to formation of waves in the outflowing material. It will take further observations and more theoretical studies to decide between these and other possible explanations.

Approximately 1,000 years ago the pattern of mass loss suddenly changed, and the Cat's Eye Nebula started forming inside the dusty shells. It has been expanding ever since, as discernible in comparing Hubble images taken in 1994, 1997, 2000, and 2002. The puzzle is what caused this dramatic change? Many aspects of the process that leads a star to lose its gaseous envelope are still poorly known, and the study of planetary nebulae is one of the few ways to recover information about these last few thousand years in the life of a Sun-like star.

Object Names: Cat's Eye Nebula, NGC 6543

Image Type: Astronomical

Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA)

Smallest terrestrial exoplanet discovered
PARIS (UPI) -- The European Space Agency says the COROT space telescope has found the smallest terrestrial planet ever detected outside the solar system.

The ESA said the newly discovered exoplanet is less than twice the size of Earth and orbits a sun-like star. Its temperature is so high -- approximately 2,000 degrees or more Fahrenheit -- it is possibly covered in lava or water vapor.

"This discovery is a very important step on the road to understanding the formation and evolution of our planet," said Malcolm Fridlund, an ESA COROT project scientist. "For the first time, we have unambiguously detected a planet that is 'rocky' in the same sense as our own Earth. We now have to understand this object further to put it into context and continue our search for smaller, more Earth-like objects with COROT."

The COROT satellite mission -- launched in December 2006 -- is led by the French Space Agency, with contributions from the ESA, Austria, Belgium, Germany, Spain and Brazil.

The discovery is to be detailed in a future issue of the journal Astronomy and Astrophysics.


Copyright 2009 by United Press International