May 9 2012

From The Space Library

RELEASE: 12-151 OVERFED BLACK HOLES SHUT DOWN GALACTIC STAR-MAKING

WASHINGTON -- The Herschel Space Observatory has shown galaxies with the most powerful, active black holes at their cores produce fewer stars than galaxies with less active black holes. The results are the first to demonstrate black holes suppressed galactic star formation when the universe was less than half its current age. Herschel is a European Space Agency-led mission with important NASA contributions. "We want to know how star formation and black hole activity are linked," said Mathew Page of University College London's Mullard Space Science Laboratory in the United Kingdom and lead author of the Nature paper describing these findings. "The two processes increase together up to a point, but the most energetic black holes appear to turn off star formation." Supermassive black holes, weighing as much as millions of suns, are believed to reside in the hearts of all large galaxies. When gas falls upon these monsters, the material is accelerated and heated around the black hole, releasing great torrents of energy. Earlier in the history of the universe, these giant, luminous black holes, called active galactic nuclei, were often much brighter and more energetic. Star formation was also livelier back then. Studies of nearby galaxies suggest active black holes can squash star formation. The revved-up, central black holes likely heat up and disperse the galactic reservoirs of cold gas needed to create new stars. These studies have only provided "snapshots" in time, however, leaving the overall relationship of active galactic nuclei and star formation unclear, especially over the cosmic history of galaxy formation. "To understand how active galactic nuclei affect star formation over the history of the universe, we investigated a time when star formation was most vigorous, between eight and 12 billion years ago," said co-author James Bock, a senior research scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., and co-coordinator of the Herschel Multi-tiered Extragalactic Survey. "At that epoch, galaxies were forming stars 10 times more rapidly than they are today on average. Many of these galaxies are incredibly luminous, more than 1,000 times brighter than our Milky Way." For the new study, Page and colleagues used Herschel data that probed 65 galaxies at wavelengths equivalent to the thickness of several sheets of office paper, a region of the light spectrum known as the far-infrared. These wavelengths reveal the rate of star formation, because most of the energy released by developing stars heats surrounding dust, which then re-radiates starlight out in far-infrared wavelengths. The researchers compared their infrared readings with X-rays streaming from the active central black holes in the survey's galaxies, measured by NASA's Chandra X-ray Observatory. At lower intensities, the black holes' brightness and star formation increased in sync. However, star formation dropped off in galaxies with the most energetic central black holes. Astronomers think inflows of gas fuel new stars and supermassive black holes. Feed a black hole too much, however, and it starts spewing radiation into the galaxy that prevents raw material from coalescing into new stars. "Now that we see the relationship between active supermassive black holes and star formation, we want to know more about how this process works," said Bill Danchi, Herschel program scientist at NASA Headquarters in Washington. "Does star formation get disrupted from the beginning with the formation of the brightest galaxies of this type, or do all active black holes eventually shut off star formation, and energetic ones do this more quickly than less active ones?" Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes and important participation by NASA. NASA's Herschel Project Office is based at JPL. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at Caltech, supports the United States astronomical community. Caltech manages JPL for NASA.

RELEASE: 12-152 NASA MARS SPACECRAFT DETECTS LARGE CHANGES IN MARTIAN SAND DUNES

WASHINGTON -- NASA's Mars Reconnaissance Orbiter (MRO) has revealed that movement in sand dune fields on the Red Planet occurs on a surprisingly large scale, about the same as in dune fields on Earth. This is unexpected because Mars has a much thinner atmosphere than Earth, is only about one percent as dense, and its high-speed winds are less frequent and weaker than Earth's. For years, researchers debated whether or not sand dunes observed on Mars were mostly fossil features related to past climate, rather than currently active. In the past two years, researchers using images from MRO's High Resolution Imaging Science Experiment (HiRISE) camera have detected and reported sand movement. Now, scientists using HiRISE images have determined that entire dunes as thick as 200 feet are moving as coherent units across the Martian landscape. The study was published online today by the journal Nature. "This exciting discovery will inform scientists trying to better understand the changing surface conditions of Mars on a more global scale," said Doug McCuistion, director of NASA's Mars Exploration Program in Washington. "This improved understanding of surface dynamics will provide vital information in planning future robotic and human Mars exploration missions." Researchers analyzed before-and-after images using a new software tool developed at the California Institute of Technology (Caltech) in Pasadena. The tool measured changes in the position of sand ripples, revealing the ripples move faster the higher up they are on a dune. The study examined images taken in 2007 and 2010 of the Nili Patera sand dune field located near the Martian equator. By correlating ripples' movement to their position on the dune, the analysis determined the entire dunes are moving. This allows researchers to estimate the volume, or flux, of moving sand. "We chose Nili Patera because we knew there was sand motion going on there, and we could quantify it," said Nathan Bridges, a planetary scientist at Johns Hopkins University Applied Physics Laboratory in Laurel, Md., and lead author of the Nature paper. "The Nili dunes also are similar to dunes in places like Antarctica and to other locations on Mars." The study adds important information about the pace at which blowing sand could be actively eroding rocks on Mars. Using the new information about the volume of sand that is moving, scientists estimate rocks in Nili Patera would be worn away at about the same pace as rocks near sand dunes in Antarctica, where similar sand fluxes occur. "Our new data shows wind activity is indeed a major agent of evolution of the landscape on Mars," said Jean-Philippe Avouac, Caltech team leader. "This is important because it tells us something about the current state of Mars and how the planet is working today, geologically." Scientists calculate that if someone stood in the Nili Patera dunes and measured out a one-yard width, they would see more than two cubic yards of sand pass by in an Earth year, about as much as in a children's sand box. "No one had estimates of this flux before," said Bridges. "We had seen with HiRISE that there was dune motion, but it was an open question how much sand could be moving. Now, we can answer that." Scientists will use the information to understand broader mysteries on Mars, like why so much of the surface appears heavily eroded, how that occurred, and whether it is a current process or it was done in the past. Scientists can now point to sand flux as a mechanism capable of creating significant erosion today on the Red Planet. The HiRISE camera provides unprecedented resolution in studying the Martian landscape. NASA's Jet Propulsion Laboratory manages MRO for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems, Denver, built the spacecraft. HiRISE is operated by the University of Arizona and was built by Ball Aerospace & Technologies Corp., Boulder, Colo.

CONTRACT RELEASE: C12-020 NASA AWARDS ENGINEERING AND SCIENCE SERVICES AND SKILLS AUGMENTATION SERVICES CONTRACT

HUNTSVILLE -- NASA has selected Jacobs Technology, Inc., of Tullahoma, Tenn., for its Engineering and Science Services and Skills Augmentation contract at Marshall Space Flight Center in Huntsville, Ala. The approximate, potential maximum quantity value of the contract, including all options, is $600 million. Jacobs will provide the continuous requirement for engineers, scientists and technicians necessary to support Marshall's Engineering Directorate; Science and Technology Office; Flight Programs and Partnerships Office; and future programs, projects and other offices with similar needs. The contract begins August 1 with a two-year base period, followed by three one-year options that may be exercised at NASA's discretion. It is a performance-based, cost-plus-fixed-fee less deductions indefinite delivery/indefinite quantity contract. Jacobs will provide all the necessary management, personnel, and equipment/supplies required to perform the engineering and science tasks as defined in contract.