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Fast-forming stars

Astronomy on 01/05/2008 at 11:45am (UTC)

A new view of a distant galaxy reveals rapid star formation.
Provided by the NRAO

The circle in the image above indicates the location of GOODS 850-5. Wang/STScI/Spitzer/NASA/NRAO/AUI/NSF [View Larger Image]December 19, 2007
A furious rate of star formation discovered in a distant galaxy shows that galaxies in the early universe developed either much faster or in a different way from what astronomers have thought.

"This galaxy is forming stars at an incredible rate," says Wei-Hao Wang, an astronomer at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The galaxy, Wang says, is forming the equivalent of 4,000 Suns a year. This is a thousand times more violent than our own Milky Way Galaxy.

The galaxy, called GOODS 850-5, is 12 billion light-years from Earth, and thus is seen as it was only about 1.5 billion years after the Big Bang. Wang and his colleagues observed it using the Smithsonian Astrophysical Observatory's Submillimeter Array (SMA) on Mauna Kea in Hawaii.

Young stars in the galaxy were enshrouded in dust that was heated by the stars and radiated infrared light strongly. Because of the galaxy's great distance from Earth, the infrared light waves have been stretched out to submillimeter-length radio waves, which are seen by the SMA. The waves were stretched or "redshifted," as astronomers say, by the ongoing expansion of the universe.

"This evidence for prolific star formation is hidden by the dust from visible-light telescopes," Wang explains. The dust, in turn, was formed from heavy elements that had to be built up in the cores of earlier stars. This indicates, Wang says, that significant numbers of stars already had formed, then spewed those heavy elements into interstellar space through supernovae explosions and stellar winds.

"Seeing the radiation from this heated dust revealed star formation we could have found in no other way," Wang says. Similar dusty galaxies in the early Universe may contain most of the star formation at those times. "This means that future telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA) can reveal many more such galaxies and give us a much more complete picture of star formation in the early Universe," he adds.

Lennox Cowie of the University of Hawaii says, "We found out in the last decade that most of the recent star formation in the universe occurs in large dusty galaxies, but we had always expected that early star formation would be dominated by smaller and less obscured galaxies. Now it seems that even at very early times it may be the same big dusty star formers that are the sites of most of the star formation. That's quite a surprise."

Astronomers believe that large galaxies originally formed through mergers of smaller objects. Seeing a large galaxy such as GOODS 850-5 forming stars so rapidly at such an early time in the history of the universe is a surprise. "Either the mergers that formed the galaxy happened much faster than we thought or some other process altogether produced the galaxy," Wang says.

Star sheds via reverse whirlpool

Astronomy on 01/05/2008 at 11:39am (UTC)

Astronomers have found the best evidence yet of matter spiraling in fountain-like jets from a young, still-forming star.
Provided by the Harvard Smithsonian CfA

This artist's concept shows a still-forming protostar which is accreting material from a surrounding disk. Some of the material from the disk, rather than falling onto the star, is ejected outward in a bipolar jet. New measurements from the Submillimeter Array show that matter in the jet is rotating around the jet's axis in a sort of "reverse whirlpool," which carries angular momentum away from the system and helps the star grow. Change Tsai (ASIAA) [View Larger Image]December 27, 2007
Astronomers have found the best evidence yet of matter spiraling outward from a young, still-forming star in fountain-like jets. Due to the spiral motion, the jets help the star to grow by drawing angular momentum from the surrounding accretion disk.

"Theorists knew that a star has to shed angular momentum as it forms," said astronomer Qizhou Zhang of the Harvard-Smithsonian Center for Astrophysics (CfA). "Now, we see evidence to back up the theory."

Angular momentum is the tendency for a spinning object to continue spinning. It applies to star formation because a star forms at the center of a rotating disk of hydrogen gas. A star grows by gathering material from the disk. However, gas cannot fall inward toward the star until that gas sheds its excess angular momentum.

As hydrogen nears the star, a fraction of the gas is ejected outward perpendicular to the disk in opposite directions, like water from a fire hose, in a bipolar jet. If the gas spirals around the axis of the jet, then it will carry angular momentum with it away from the star.

Using the Submillimeter Array (SMA), an international team of astronomers observed an object called Herbig-Haro (HH) 211, located about 1,000 light-years away in the constellation Perseus. HH 211 is a bipolar jet traveling through interstellar space at supersonic speeds. The central protostar is about 20,000 years old with a mass only six percent the mass of our Sun. It eventually will grow into a star like the Sun.

The astronomers found clear evidence for rotation in the bipolar jet. Gas within the jet swirls around at speeds of more than 3,000 miles per hour, while also blasting away from the star at a velocity greater than 200,000 miles per hour.

"HH 211 essentially is a 'reverse whirlpool.' Instead of water swirling around and down into a drain, we see gas swirling around and outward," explained Zhang.

In the future, the team plans to take a closer, more detailed look at HH 211. They also hope to observe additional protostar-jet systems.

"These are intrinsically difficult measurements. We need narrow jets to be able to detect signs of rotation, and they have to be close enough for us to observe them with high resolution," said CfA astronomer Tyler Bourke. "There are very few jets around that meet those criteria."

The technological capabilities of the SMA were crucial in gathering these data.

"The SMA has been in operation since the end of 2003. It has hit its scientific stride and is producing a substantial amount of high-quality scientific results," said SMA director Ray Blundell.

In the more distant future, new ground-based observatories will turn their powerful gaze on this and other newborn stars.

ASIAA Director Paul Ho notes, "A much more powerful radio interferometer, the Atacama Large Millimeter/Submillimeter Array (ALMA), is now under construction in northern Chile, as a much more powerful version of the SMA. It will allow us to zoom in to these stellar birthplaces with much finer details and unravel the process of stellar birth directly."

A paper on this work was published in the December 1 issue of the Astrophysical Journal.

Atlantis to Help Mark NASCAR Milestone

Nasa on 01/05/2008 at 11:38am (UTC)

A trio of flags from the Daytona 500 will set speed marks of their own as they race to 17,500 mph aboard space shuttle Atlantis.

The green starter's flags are tucked inside the shuttle during the STS-122 mission to the International Space Station. One of the flags will be waved to begin the 2008 installment of what NASCAR calls the "Great American Race," while another will be presented to the winning driver. NASA will keep the third.

While NASA celebrates its 50th anniversary, the Daytona International Speedway is celebrating the 50th running of the Daytona 500 in 2008. Drivers and their crews have been known to pause at the race track to watch a shuttle streak into space on a plume of fire and smoke. The track is less than 100 miles from the shuttle launch pads at NASA's Kennedy Space Center on Florida's east coast.

Over the years, technology developed for the space program has found many uses on Earth, even helping NASCAR drivers stay safe and increase their performance. NASCAR drivers wear cooling suits very similar to what astronauts wear during spacewalks. Foam NASA developed for aircraft seats protects racecar drivers’ necks in a crash. And the same material that protects the space shuttle from extreme temperatures when it re-enters the atmosphere protects NASCAR drivers from the heat of their high-performance engines.

NASA and astronauts often pack mementoes aboard space shuttle flights to commemorate historical events, mark milestones and celebrate achievements. The effort also brings awareness of the space agency to a wider audience and gives people a chance to see a tangible sign of exploration.

Atlantis will also carry a dried red rose that will be woven into a NASA-themed float during the Tournament of Roses parade. The float also will celebrate NASA's first 50 years in existence.

The manifest of commemorative cargo takes on a bit of a European accent during STS-122 because the Columbus laboratory Atlantis will install on the International Space Station was developed and built in Europe. The cutting-edge research module will be used by institutions based in Europe to study space and the effects of weightlessness.

The special items for European representatives include dozens of fabric patches for the Columbus program, a host of decals and 20 flags representing the European Space Agency. More than 500 pins representing the STS-122 mission are also stowed inside Atlantis.

The seven crew members packed a number of items of their own, usually representing schools they attended or units they served in. There is even a deflated football from the University of Richmond's Athletic Department. Mission Specialist Leland Melvin attended the University of Richmond and played professional football before joining NASA.

The items are packed to take up very little room inside lockers onboard Atlantis. Commemorative items are also chosen to weigh very little, but carry a big impact upon their return to Earth.

Steven Siceloff
Kennedy Space Center

Dust in the wind

Astronomy on 01/05/2008 at 11:35am (UTC)

Astronomers have found 10,000 Earths' worth of fresh dust near a star explosion.
Provided by the Jet Propulsion Laboratory

Dusty grains -- including tiny specks of the minerals found in the gemstones peridot, sapphires, and rubies -- can be seen blowing in the winds of a quasar, or active black hole, in this artist's concept. The quasar is at the center of a distant galaxy. NASA/JPL-Caltech/T. Pyle (SSC) [View Larger Image]December 20, 2007
Astronomers have at last found definitive evidence that the universe's first dust, the celestial stuff that seeded future generations of stars and planets, was forged in the explosions of massive stars.

The findings, made with NASA's Spitzer Space Telescope, are the most significant clue yet in the longstanding mystery of where the dust in our very young universe came from. Scientists had suspected that exploding stars, or supernovae, were the primary source, but nobody had been able to demonstrate that they can create copious amounts of dust, until now. Spitzer's sensitive infrared detectors have found 10,000 Earth masses worth of dust in the blown-out remains of the well-known supernova remnant Cassiopeia A.

"Now we can say unambiguously that dust, and lots of it, was formed in the ejecta of the Cassiopeia A explosion. This finding was possible because Cassiopeia A is in our own galaxy, where it is close enough to study in detail," says Jeonghee Rho of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena.

Space dust is everywhere in the cosmos, in our own neck of the universe and all the way back billions of light-years away in our infant universe. Developing stars need dust to cool down enough to collapse and ignite, while planets and living creatures consist of the powdery substance. In our nearby universe, dust is pumped out by dying stars like our Sun. But back when the universe was young, Sun-like stars hadn't been around long enough to die and leave dust.

This plot of data captured by NASA's Spitzer Space Telescope reveals dust entrained in the winds rushing away from a quasar. NASA/JPL-Caltech/F. Markwick-Kemper (University of Manchester) [View Larger Image]That's where supernovae come in. These violent explosions occur when the most massive stars in the universe die. Because massive stars don't live very long, theorists reasoned that the very first exploding massive stars could be the suppliers of the unaccounted-for dust. These first stars, called Population III, are the only stars that formed without any dust.

Rho and her colleagues analyzed the Cassopeia A supernova remnant, located about 11,000 light-years away. Though this remnant is not from the early universe, its proximity to us makes it easier to address the question of whether supernovae have the ability to synthesize significant amounts of dust. The astronomers analyzed the infrared light coming from Cassiopeia A using Spitzer's infrared spectrograph, which spreads light apart to reveal the signatures of different elements and molecules. "Because Spitzer is extremely sensitive to dust, we were able to make high-resolution maps of dust in the entire structure," says Rho.

The map reveals the quantity, location and composition of the supernova remnant's dust, which includes proto-silicates, silicon dioxide, iron oxide, pyroxene, carbon, aluminium oxide and other compounds. One of the first things the astronomers noticed was that the dust matches up perfectly with the gas, or ejecta, known to have been expelled in the explosion. This is the smoking gun indicating the dust was freshly made in the ejecta from the stellar blast. "Dust forms a few to several hundred days after these energetic explosions, when the temperature of gas in the ejecta cools down," says Takashi Kozasa, a co-author at the Hokkaido University in Japan.

This extraordinarily deep Chandra image shows Cassiopeia A , the supernova where the dust was found. Chandra Observatory [View Larger Image]The team was surprised to find freshly-made dust deeper inside the remnant as well. This cooler dust, mixed in with gas referred to as the unshocked ejecta, had never been seen before.

All the dust around the remnant, both warm and cold, adds up to about three percent of the mass of the Sun, or 10,000 Earths. This is just enough to explain where a large fraction, but not all, of the universe's early dust came from. "Perhaps at least some of the unexplained portion is much colder dust, which could be observed with upcoming telescopes, such as Herschel," says Haley Gomez, a co-author at University of Wales, Cardiff.

Rho also said that more studies of other supernovae from near to far are needed to put this issue to rest. She notes that the rate at which dust is destroyed - a factor in determining how much dust is needed to explain the dusty early universe - is still poorly understood.

New camera for detecting exoplanets

Astronomy on 01/05/2008 at 11:31am (UTC)

The Subaru Telescope will utilize a new instrument in the hunt for planets beyond our solar system.
Provided by the NAOJ

The Subaru dome (left) has a new tool for finding exoplanets: the High Contrast Instrument for the Subaru Next Generation Adaptive Optics. David J. Eicher [View Larger Image]December 28, 2007
The Subaru Telescope, located on the summit of Mauna Kea, is dedicated to exploring the cosmos, gaining a deeper and more thorough understanding of everything that surrounds us. With an 8.2-meter mirror and a suite of sophisticated instruments, astronomers at Subaru Telescope explore nearby stars looking for planetary systems. A giant step towards this goal was made recently with the "first-light" inauguration of a new state-of-the-art instrument.

There are eight innovative cameras and spectrographs at Subaru optimized for various astronomical investigations in optical and near-infrared wavelengths. On the night of December 3, 2007, a new instrument was brought to life, HiCIAO (High Contrast Instrument for the Subaru Next Generation Adaptive Optics). The HiCIAO camera is designed as a technologically adaptable system that will replace the infrared CIAO (Coronagraphic Imager with Adaptive Optics) unit that has been in operation since April 2000. Both systems are designed to block out the harsh direct light from a star, so that nearby faint objects such as planets can be viewed. The new system benefits from a contrast improvement of 10 to 100 times better than before, allowing astronomers glimpses into regions never explored. A further advantage of the HiCIAO camera is that it will be used in concert with an adaptive optics (AO) system that was recently significantly upgraded, which, in turn, increased the clarity of Subaru's vision by a factor of ten, opening up more of the night sky to observing. The new AO system uses 188 actuators behind a deformable mirror to remove the atmospheric distortion from its view, allowing Subaru Telescope to observe close to its theoretical performance limits. In conjunction with the new AO system a laser guide star system was installed so that any part of the sky can now be observed.

The HiCIAO system, initiated in 2004, was developed by an ambitious team of scientists and engineers from the Subaru Telescope, National Astronomical Observatory of Japan, and the University of Hawaii's Institute for Astronomy. Dr. Ryuji Suzuki, a Subaru astronomer leading the HiCIAO project, says "the unique instrument was primarily designed for the direct detection of extrasolar planets and disks". The system's innovative design allows for high contrast coronagraphic techniques in three observing modes: direct imaging, polarization differential imaging, and spectral differential imaging. HiCIAO directly detects and characterizes young extrasolar planets and brown dwarfs, sub-stellar objects that occupy the mass range between that of large gas giant planets (e.g. Jupiter) and the lowest mass stars. With the aid of the laser guide star AO system, HiCIAO targets dim objects including young stars, protostars, and star forming regions. HiCIAO is also extremely useful detecting faint dust disks around nearby stars studying small-scale and inner disk structures and dust grain properties, leading to a clearer understanding of extra-solar planetary systems and their evolutionary processes. Dr. Suzuki reports that "although we already know more than 250 extrasolar planets, they have all proven their existence by indirect evidences like the Doppler or transit method. Because the direct imaging of an extrasolar planet has never been done, if it happens, that will be exciting". Subaru Telescope hopes to be the first to directly observe a planet outside our solar system.

Anatomy of a bird

Astronomy on 01/05/2008 at 11:30am (UTC)

VLT's NACO instrument reveals a triple cosmic collision.
Provided by the ESO

A 30-min VLT/NACO K-band exposure has been combined with archive HST/ACS B and I-band images to produce a three-color image of the 'Bird' interacting galaxy system. ESO/Henri Boffin [View Larger Image]December 21, 2007
Using ESO's Very Large Telescope, an international team of astronomers has discovered a stunning rare case of a triple merger of galaxies. This system, which astronomers have dubbed "The Bird," is composed of two massive spiral galaxies and a third irregular galaxy.

The galaxy ESO 593-IG 008, or IRAS 19115-2124, was previously known as an interacting pair of galaxies at a distance of 650 million light-years. But surprises were revealed by observations made with the NACO instrument attached to ESO's Very Large Telescope, which peered through the all-pervasive dust clouds, using adaptive optics to resolve the finest details.

Underneath the chaotic appearance of the optical Hubble images, retrieved from the Hubble Space Telescope archive, the NACO images show two unmistakable galaxies, one a barred spiral while the other is more irregular.

The surprise lay in the clear identification of a third, clearly separate component, an irregular, yet fairly massive galaxy that seems to be forming stars at a frantic rate.

"Examples of mergers of three galaxies of roughly similar sizes are rare," says Petri Vaisanen, lead author of the paper reporting the results. "Only the near-infrared VLT observations made it possible to identify the triple merger nature of the system in this case."

This image was taken with the NACO instrument on ESO's Very Large Telescope in the K-band and indicates the different parts of the Bird. NACO/VLT [View Larger Image]Because of the resemblance of the system to a bird, the object was dubbed as such, with the "head" being the third component, and the "heart" and "body" making the two major galaxy nuclei in-between of tidal tails, the "wings." The latter extend more than 100,000 light-years, or the size of our own Milky Way.

Subsequent optical spectroscopy with the new Southern African Large Telescope, and archive mid-infrared data from the NASA Spitzer space observatory, confirmed the separate nature of the head, but also added further surprises. The head and major parts of the "Bird" are moving apart at more than 400 km/s (1.4 million km/h). Observing such high velocities is very rare in merging galaxies. Also, the head appears to be the major source of infrared luminosity in the system, though it is the smallest of the three galaxies.

"It seems that NACO has caught the action right at the time of the first high-speed fly-by of the 'head' galaxy through the system consisting of the other two galaxies," says Seppo Mattila, member of the discovery team. "These two galaxies must have met earlier, probably a couple of hundred million years ago."

The head is forming stars violently, at a rate of nearly 200 solar masses per year, while the other two galaxies appear to be at a more quiescent epoch of their interaction-induced star formation history.

The Bird belongs to the prestigious family of luminous infrared galaxies, with an infrared luminosity nearly 1000 billion times that of the Sun. This family of galaxies has long been thought to signpost important events in galaxy evolution, such as mergers of galaxies, which in turn trigger bursts of star formation, and may eventually lead to the formation of a single elliptical galaxy.

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