Newborn Stars Emerge from Dark Clouds in Taurus

A new image from the APEX (Atacama Pathfinder Experiment) telescope in Chile shows a sinuous filament of cosmic dust more than ten light-years long. In it, newborn stars are hidden, and dense clouds of gas are on the verge of collapsing to form yet more stars. It is one of the regions of star formation closest to us. The cosmic dust grains are so cold that observations at wavelengths of around one millimetre, such as these made with the LABOCA camera on APEX, are needed to detect their faint glow.


The Taurus Molecular Cloud, in the constellation of Taurus (The Bull), lies about 450 light-years from Earth. This image shows two parts of a long, filamentary structure in this cloud, which are known as Barnard 211 and Barnard 213. Their names come from Edward Emerson Barnard's photographic atlas of the "dark markings of the sky," compiled in the early 20th century. In visible light, these regions appear as dark lanes, lacking in stars. Barnard correctly argued that this appearance was due to "obscuring matter in space."
We know today that these dark markings are actually clouds of interstellar gas and dust grains. The dust grains -- tiny particles similar to very fine soot and sand -- absorb visible light, blocking our view of the rich star field behind the clouds. The Taurus Molecular Cloud is particularly dark at visible wavelengths, as it lacks the massive stars that illuminate the nebulae in other star-formation regions such as Orion. The dust grains themselves also emit a faint heat glow but, as they are extremely cold at around -260 degrees Celsius, their light can only be seen at wavelengths much longer than visible light, around one millimetre.
These clouds of gas and dust are not merely an obstacle for astronomers wishing to observe the stars behind them. In fact, they are themselves the birthplaces of new stars. When the clouds collapse under their own gravity, they fragment into clumps. Within these clumps, dense cores may form, in which the hydrogen gas becomes dense and hot enough to start fusion reactions: a new star is born. The birth of the star is therefore surrounded by a cocoon of dense dust, blocking observations at visible wavelengths. This is why observations at longer wavelengths, such as the millimetre range, are essential for understanding the early stages of star formation.
The upper-right part of the filament shown here is Barnard 211, while the lower-left part is Barnard 213. The millimetre-range observations from the LABOCA camera on APEX, which reveal the heat glow of the cosmic dust grains, are shown here in orange tones, and are superimposed on a visible light image of the region, which shows the rich background of stars. The bright star above the filament is φ Tauri, while the one partially visible at the left-hand edge of the image is HD 27482. Both stars are closer to us than the filament, and are not associated with it.
Observations show that Barnard 213 has already fragmented and formed dense cores -- as illustrated by the bright knots of glowing dust -- and star formation has already happened. However, Barnard 211 is in an earlier stage of its evolution; the collapse and fragmentation is still taking place, and will lead to star formation in the future. This region is therefore an excellent place for astronomers to study how Barnard's "dark markings of the sky" play a crucial part in the lifecycle of stars.
The observations were made by Alvaro Hacar (Observatorio Astronómico Nacional-IGN, Madrid, Spain) and collaborators. The LABOCA camera operates on the 12-metre APEX telescope, on the plateau of Chajnantor in the Chilean Andes, at an altitude of 5000 metres. APEX is a pathfinder for the next generation submillimetre telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), which is being built and operated on the same plateau.

Globular Clusters: Survivors of a 13-Billion-Year-Old Massacre

Our Milky Way galaxy is surrounded by some 200 compact groups of stars, containing up to a million stars each. At 13 billion years of age, these globular clusters are almost as old as the universe itself and were born when the first generations of stars and galaxies formed. Now a team of astronomers from Germany and the Netherlands have conducted a novel type of computer simulation that looked at how they were born -- and they find that these giant clusters of stars are the only survivors of a 13-billion-year-old massacre that destroyed many of their smaller siblings.
The new work, led by Dr Diederik Kruijssen of the Max Planck Institute for Astrophysics in Garching, Germany, appears in a paper in the journal Monthly Notices of the Royal Astronomical Society.
Globular star clusters have a remarkable characteristic: the typical number of stars they contain appears to be about the same throughout the Universe. This is in contrast to much younger stellar clusters, which can contain almost any number of stars, from fewer than 100 to many thousands. The team of scientists proposes that this difference can be explained by the conditions under which globular clusters formed early on in the evolution of their host galaxies.
The researchers ran simulations of isolated and colliding galaxies, in which they included a model for the formation and destruction of stellar clusters. When galaxies collide, they often generate spectacular bursts of star formation (“starbursts”) and a wealth of bright, young stellar clusters of many different sizes. As a result it was always thought that the total number of star clusters increases during starbursts. But the Dutch-German team found the opposite result in their simulations.
While the very brightest and largest clusters were indeed capable of surviving the galaxy collision due to their own gravitational attraction, the numerous smaller clusters were effectively destroyed by the rapidly changing gravitational forces that typically occur during starbursts due to the movement of gas, dust and stars. The wave of starbursts came to an end after about 2 billion years and the researchers were surprised to see that only clusters with high numbers of stars had survived. These clusters had all the characteristics that should be expected for a young population of globular clusters as they would have looked about 11 billion years ago.
Dr Kruijssen comments: “It is ironic to see that starbursts may produce many young stellar clusters, but at the same time also destroy the majority of them. This occurs not only in galaxy collisions, but should be expected in any starburst environment. In the early Universe, starbursts were commonplace – it therefore makes perfect sense that all globular clusters have approximately the same large number of stars. Their smaller brothers and sisters that didn’t contain as many stars were doomed to be destroyed.”
According to the simulations, most of the star clusters were destroyed shortly after their formation, when the galactic environment was still very hostile to the young clusters. After this episode ended, the surviving globular clusters have lived quietly until the present day.
The researchers have further suggestions to test their ideas. Dr Kruijssen continues: “In the nearby Universe, there are several examples of galaxies that have recently undergone large bursts of star formation. It should therefore be possible to see the rapid destruction of small stellar clusters in action. If this is indeed found by new observations, it will confirm our theory for the origin of globular clusters.”
The simulations suggest that most of a globular cluster’s traits were established when it formed. The fact that globular clusters are comparable everywhere then indicates that the environments in which they formed were very similar, regardless of the galaxy they currently reside in. In that case, Dr Kruijssen believes, they can be used as fossils to shed more light on the conditions in which the first stars and galaxies were born.

The above story is reprinted from materials provided by Royal Astronomical Society (RAS), via AlphaGalileo.

NASA's Chandra Finds Milky Way's Black Hole Grazing on Asteroids

 The giant black hole at the center of the Milky Way may be vaporizing and devouring asteroids, which could explain the frequent flares observed, according to astronomers using data from NASA's Chandra X-ray Observatory.

For several years Chandra has detected X-ray flares about once a day from the supermassive black hole known as Sagittarius A*, or "Sgr A*" for short. The flares last a few hours with brightness ranging from a few times to nearly one hundred times that of the black hole's regular output. The flares also have been seen in infrared data from ESO's Very Large Telescope in Chile.

"People have had doubts about whether asteroids could form at all in the harsh environment near a supermassive black hole," said Kastytis Zubovas of the University of Leicester in the United Kingdom, and lead author of the report appearing in the Monthly Notices of the Royal Astronomical Society. "It's exciting because our study suggests that a huge number of them are needed to produce these flares."

Zubovas and his colleagues suggest there is a cloud around Sgr A* containing trillions of asteroids and comets, stripped from their parent stars. Asteroids passing within about 100 million miles of the black hole, roughly the distance between the Earth and the sun, would be torn into pieces by the tidal forces from the black hole.

These fragments then would be vaporized by friction as they pass through the hot, thin gas flowing onto Sgr A*, similar to a meteor heating up and glowing as it falls through Earth's atmosphere. A flare is produced and the remains of the asteroid are swallowed eventually by the black hole.

"An asteroid's orbit can change if it ventures too close to a star or planet near Sgr A*," said co-author Sergei Nayakshin, also of the University of Leicester. "If it's thrown toward the black hole, it's doomed."

The authors estimate that it would take asteroids larger than about six miles in radius to generate the flares observed by Chandra. Meanwhile, Sgr A* also may be consuming smaller asteroids, but these would be difficult to spot because the flares they generate would be fainter.

These results reasonably agree with models estimating of how many asteroids are likely to be in this region, assuming that the number around stars near Earth is similar to the number surrounding stars near the center of the Milky Way.

"As a reality check, we worked out that a few trillion asteroids should have been removed by the black hole over the 10-billion-year lifetime of the galaxy," said co-author Sera Markoff of the University of Amsterdam in the Netherlands. "Only a small fraction of the total would have been consumed, so the supply of asteroids would hardly be depleted."

Planets thrown into orbits too close to Sgr A* also should be disrupted by tidal forces, although this would happen much less frequently than the disruption of asteroids, because planets are not as common. Such a scenario may have been responsible for a previous X-ray brightening of Sgr A* by about a factor of a million about a century ago. While this event happened many decades before X-ray telescopes existed, Chandra and other X-ray missions have seen evidence of an X-ray "light echo" reflecting off nearby clouds, providing a measure of the brightness and timing of the flare.

"This would be a sudden end to the planet's life, a much more dramatic fate than the planets in our solar system ever will experience," Zubovas said.

Very long observations of Sgr A* will be made with Chandra later in 2012 that will give valuable new information about the frequency and brightness of flares and should help to test the model proposed here to explain them. This work could improve understanding about the formation of asteroids and planets in the harsh environment of Sgr A*.

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.

For Chandra images, multimedia and related materials, visit:

http://www.nasa.gov/chandra

For an additional interactive image, podcast, and video on the finding, visit:

http://chandra.si.edu

NASA Mission Takes Stock of Earth's Melting Land Ice

In the first comprehensive satellite study of its kind, a University of Colorado at Boulder-led team used NASA data to calculate how much Earth's melting land ice is adding to global sea level rise.

Using satellite measurements from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE), the researchers measured ice loss in all of Earth's land ice between 2003 and 2010, with particular emphasis on glaciers and ice caps outside of Greenland and Antarctica.

The total global ice mass lost from Greenland, Antarctica and Earth's glaciers and ice caps during the study period was about 4.3 trillion tons (1,000 cubic miles), adding about 0.5 inches (12 millimeters) to global sea level. That's enough ice to cover the United States 1.5 feet (0.5 meters) deep.

"Earth is losing a huge amount of ice to the ocean annually, and these new results will help us answer important questions in terms of both sea rise and how the planet's cold regions are responding to global change," said University of Colorado Boulder physics professor John Wahr, who helped lead the study. "The strength of GRACE is it sees all the mass in the system, even though its resolution is not high enough to allow us to determine separate contributions from each individual glacier."

About a quarter of the average annual ice loss came from glaciers and ice caps outside of Greenland and Antarctica (roughly 148 billion tons, or 39 cubic miles). Ice loss from Greenland and Antarctica and their peripheral ice caps and glaciers averaged 385 billion tons (100 cubic miles) a year. Results of the study will be published online Feb. 8 in the journal Nature.

Traditional estimates of Earth's ice caps and glaciers have been made using ground measurements from relatively few glaciers to infer what all the world's unmonitored glaciers were doing. Only a few hundred of the roughly 200,000 glaciers worldwide have been monitored for longer than a decade.

One unexpected study result from GRACE was the estimated ice loss from high Asian mountain ranges like the Himalaya, the Pamir and the Tien Shan was only about 4 billion tons of ice annually. Some previous ground-based estimates of ice loss in these high Asian mountains have ranged up to 50 billion tons annually.

"The GRACE results in this region really were a surprise," said Wahr, who also is a fellow at the University of Colorado-headquartered Cooperative Institute for Research in Environmental Sciences. "One possible explanation is that previous estimates were based on measurements taken primarily from some of the lower, more accessible glaciers in Asia and extrapolated to infer the behavior of higher glaciers. But unlike the lower glaciers, most of the high glaciers are located in very cold environments and require greater amounts of atmospheric warming before local temperatures rise enough to cause significant melting. This makes it difficult to use low-elevation, ground-based measurements to estimate results from the entire system."

"This study finds that the world's small glaciers and ice caps in places like Alaska, South America and the Himalayas contribute about .02 inches per year to sea level rise," said Tom Wagner, cryosphere program scientist at NASA Headquarters in Washington. "While this is lower than previous estimates, it confirms that ice is being lost from around the globe, with just a few areas in precarious balance. The results sharpen our view of land ice melting, which poses the biggest, most threatening factor in future sea level rise."

The twin GRACE satellites track changes in Earth's gravity field by noting minute changes in gravitational pull caused by regional variations in Earth's mass, which for periods of months to years is typically because of movements of water on Earth's surface. It does this by measuring changes in the distance between its two identical spacecraft to one-hundredth the width of a human hair.

The GRACE spacecraft, developed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., and launched in 2002, are in the same orbit approximately 137 miles (220 kilometers) apart.

For more on GRACE, visit:

http://www.csr.utexas.edu/grace

http://grace.jpl.nasa.gov

For more information about NASA and agency programs, visit:

http://www.nasa.gov

NASA Seeks Game Changing Technology Payloads for Suborbital Research Flights

NASA is seeking proposals for small technology payloads that could fly on future NASA-sponsored suborbital flights. These future flights will travel to the edge of space and back, testing the innovative new technologies before they're sent to work in the harsh environment of space.

"NASA's Game Changing Development Program focuses on maturing advanced space technologies that may lead to entirely new approaches for the agency's future space missions while providing solutions to significant national needs and adding to our nation’s innovation economy," said Michael Gazarik, director of NASA's Space Technology Program at NASA Headquarters in Washington. "This solicitation offers an opportunity to develop potentially transformative technologies that take advantage of our Flight Opportunities Program platforms, which allow frequent and predictable commercial access to near-space, with easy recovery of intact payloads."

NASA's Game Changing Opportunities research announcement seeks proposals for payloads, vehicle enhancements and onboard facilities for payload integration that will help the agency advance technology development in the areas of exploration, space operations and other innovative technology areas relevant to NASA's missions. Sponsored by NASA's Space Technology Program, the agency expects proposals from entrepreneurs, scientists, technologists, instrument builders, research managers, and vehicle builders and operators.

"This call for proposals is a great opportunity to develop innovative technology development payloads for flight on commercial suborbital, reusable vehicles which have novel ideas and approaches have the potential to revolutionize future space missions," said Stephen Gaddis, Game Changing Development program manager at NASA's Langley Research Center in Hampton, Va.

Special emphasis will be given to proposals that address basic and applied research as well as development for advanced technologies and the development of test articles and techniques for evaluating the articles. Following development, selected payloads will be made available to NASA's Flight Opportunities Program for pairing with appropriate suborbital reusable launch service provider flights.

In August 2011, NASA selected seven U.S. companies that can provide flight services and platforms to test innovative technology payloads through the Flight Opportunities Program. Under this solicitation, the selected Flight Opportunities suborbital reusable launch vehicles could be modified to facilitate integration and payload engineering of future payloads in support of specific research needs.

Proposals will be accepted from U.S. or non-U.S. organizations including NASA centers and other government agencies, federally funded research and development centers, educational institutions, industry and nonprofit organizations.

NASA expects to make approximately 20 awards this summer, with the majority of awards ranging between approximately $50,000 and $125,000 each. Several awards may be made for up to $500,000 in the area of vehicle integration and payload engineering technology enhancements and onboard research facilities to improve platform capabilities.

The Game Changing Opportunities in Technology Development research announcement is available through the NASA Solicitation and Proposal Integrated Review and Evaluation System website at:

http://tinyurl.com/7xk52wa

NASA's Langley Research Center manages the Game Changing Development Program and NASA's Dryden Flight Research Center at Edwards, Calif., manages the Flight Opportunities Program for the agency's Space Technology Program.

For more information on the Game Changing Development activities and information on this solicitation for payloads, visit:

http://go.usa.gov/RPS

For more information about NASA's Flight Opportunities Program, visit:

http://go.usa.gov/REv

Station Astronauts Capture Stunning Views of U.S., Canada, Northern Lights

Astronauts aboard the International Space Station recently filmed what is among the most spectacular night imagery ever taken from space of the United States. The video, comprised of hundreds of sequential still images, will air on NASA Television's video file beginning today.

The imagery also is available on the internet at NASA's Gateway to Astronaut Photography of Earth:

http://eol.jsc.nasa.gov

Taken between Jan. 29-Feb. 3, the images show a continent ablaze with light, from the electric glow of hundreds of cities to a spectacular aurora borealis flickering on the northern horizon. The video includes flights above Mexico showing the entire Gulf Coast and continuing the length of the East Coast. Other video capture scenes from Brownsville, Texas, to the Great Lakes and above the St. Lawrence Seaway. Still another sequence begins in the western U.S. and continues across the Great Plains.

New imagery also shows the aurora during flights above Canada. The imagery was taken using a still camera aboard the station, orbiting 240 miles above Earth. For more about the International Space Station, visit:

http://www.nasa.gov/station

For NASA Television schedules, downlink information and streaming video, visit:

 

http://www.nasa.gov/ntv

Putting the Squeeze On Planets Outside Our Solar System

Just as graphite can transform into diamond under high pressure, liquid magmas may similarly undergo major transformations at the pressures and temperatures that exist deep inside Earth-like planets.
Using high-powered lasers, scientists at Lawrence Livermore National Laboratory and collaborators discovered that molten magnesium silicate undergoes a phase change in the liquid state, abruptly transforming to a more dense liquid with increasing pressure. The research provides insight into planet formation.
"Phase changes between different types of melts have not been taken into account in planetary evolution models," said lead scientist Dylan Spaulding, a University of California, Berkeley graduate student who conducted most of his thesis work at the Laboratory's Jupiter Laser Facility. "But they could have played an important role during Earth's formation and may indicate that extra-solar 'Super-Earth' planets are structured differently from Earth."
Melts play a key role in planetary evolution. The team said that pressure-induced liquid-liquid phase separation in silicate magmas may represent an important mechanism for global-scale chemical differentiation and also may influence the thermal transport and convective processes that govern the formation of a mantle and core early in planetary history. Liquid-liquid phase separation is similar to the difference between oil and vinegar -- they want to separate because they have different densities. In the new research, however, the researchers noticed a sudden change between liquid states of silicate magma that displayed different physical properties even though they both have the same composition when high pressure and temperatures were applied.
The team used LLNL's Janus laser and OMEGA at the University of Rochester to conduct the experiments to achieve the extreme temperatures and pressures that exist in the interiors of exoplanets -- those objects outside our solar system.
In each experiment, a powerful laser pulse generated a shock wave while it traveled through the sample. By looking for changes in the velocity of the shock and the temperature of the sample, the team was able to identify discontinuities that signaled a phase change in the material.
"In this case, the decay in shock-velocity and thermal emission both reverse themselves during the same brief time interval," Spaulding said.
The team concluded that a liquid-liquid phase transition in a silicate composition similar to what would be found in terrestrial planetary mantles could help explain the thermal-chemical evolution of exoplanet interiors.
The research appears in the Feb. 10 edition of the journal, Physical Review Letters.
Other LLNL authors include Jon Eggert, Peter Celliers, Damien Hicks, Gilbert Collins and Ray Smith. Other collaborators include UC Berkeley, the Carnegie Institution of Washington and Howard University.
The work was funded by the National Nuclear Security Administration, the National Science Foundation and the University of California.
The above story is reprinted from materials provided by DOE/Lawrence Livermore National Laboratory.