 | | | | | | | | | | |  |  | | | | Space: Dark Matters: New Telescope to Seek Elusive Matter and Energy">3. Space News | | | | | | | 
3. Space News | News submitted by: MIB
NEW YORK, New York -- There are dark forces at work in this universe of ours, hidden from the naked eye but affecting everything from the mass of galaxies to the shape of the universe.
Astronomers attribute these forces to dark matter and dark energy, unseen phenomena whose existence can be inferred -- if not seen directly -- though other sky observations. A better understanding of these forces could help researchers determine how the universe evolved.
A group of research organizations are hoping to build a new telescope that might just do the trick, scanning the entire visible night sky repeatedly over a period of years. The telescope, researchers hope, will prove itself invaluable for finding dark matter and dark energy, as well as tracking near-Earth asteroids, supernovae and other astronomical phenomena.
"We're looking to cover a wide field of view, look deep into space and do it fast," said project director Anthony Tyson, of Lucent Technology's Bell Labs in Murray Hill, New Jersey. "And there's a huge laundry list of astronomy that we could do with it."
Seeing the 'dark' of space
Tyson is directing efforts to design and build the Large Synoptic Survey Telescope (LSST) by the LSST Corporation Inc., a collective of professional research groups and academic universities working to make the telescope a reality. The telescope is expected to go online by 2011.
Project designers plan to equip their telescope with both a wide field of view and an extremely sensitive digital camera, a combination that should allow LSST to make a comprehensive sky survey in about four days. The process can then be repeated over and over again to compare changes in objects and asteroids.
"But when you look at the night sky, you can only see things that glow in the dark," Tyson said. "They are really just a minor constituent, a minor player in the dynamical game." Dark matter is the real heavy hitter, he added
LSST scientists will to use weak gravitational lensing of the most distant objects in the universe to detect dark matter. Gravitational lensing occurs when light from a distant galaxy or other object is distorted by the gravitational pull of the matter between it and observer's on Earth. The phenomenon is also known as cosmological shear. By measuring the amount of distortion of an object, LSST researchers will be able to map dark matter across the night sky.
Weak gravitational lensing can also be used to detect dark energy, a mysterious force thought by some to be responsible for the continued expansion of the universe. In 1998, astronomers studying supernovae found them to be moving faster than they expected, leading them to postulate that some force -- now called dark energy - had imparted the additional acceleration.
LSST should be able to measure dark energy by observing its effects on cosmic structures in two ways. First, it will seek out massive clusters of material, such as a group of galaxies, over a timeframe of between 1 billion to 8 billion years to form three-dimensional maps of each region's mass. Charting the growth of these regions over time should give researchers an idea of how much dark energy is present.
The telescope should also be able to measure dark energy through observations of the overall redshift of the night sky using weak gravitational shear. Objects moving away from earth emit light closer to red end, or redshifted, of the visible light spectrum.
"Those two measurements get at the physics of dark energy, and both are complimentary to each other," Tyson said. "One cannot just rely on just one of these methods, such as the supernovae measurements for example, because there are degeneracies that appear and a multitude of theoretical ways in which you could explain the results of supernovae data."
The repetitiveness of LSST's sky surveys will also come in handy for asteroid-hunters hoping to chart rogue space rocks before they pose a danger to Earth. Researchers expect the instrument to be able to image up to 10,000 trans-Neptunian objects and 100,000 previously unknown supernovae each year.
LSST
Current LSST designs call for an 8.4-meter telescope, which wouldn't make it the largest telescope ever made (the 10-meter telescopes at the W.M. Keck Observatory in Hawaii have that title) but size isn't what project researchers are after.
"It really is a completely different way of doing astronomy," said Philip Pinto, an astronomy professor at the University of Arizona, which is part of LSST Corp. "It's dedicated to things that change, that's the synoptic part." T he project was named as one of the top priorities in ground-based astronomy by the National Academy of Sciences' Decadal Survey of astronomy, he added.
LSST is expected to observe about three degrees of the sky at a time. Astronomers measure the size of stars and other objects in terms of degrees, arcminutes and arcseconds. The moon, for example, is about 30 arcminutes (half a degree) wide. There are 60 arcseconds in an arcminute and 60 arcminutes in one degree.
To put LSST's field of view in perspective, the Keck telescopes can survey a maximum are of about 81.5 arcminutes (or about 1.35 degrees) using their DEIMOS spectrograph, which uses a 64-million pixel CCD camera to make detailed observations. In addition to its consistent three-degree view, LSST will use a digital camera with more than two billion pixels, allowing it to detect some of the oldest and faintest objects in the night sky.
"This instrument should open the time window," Tyson said. "LSST goes so faint, so fast, that it should be able to detect things like optical flashes or [gamma ray bursters] from the edge of the universe."
The telescope should collect about five terabytes of sky data per day of operation. The Hubble Space Telescope, for comparison, produces about one terabyte each year, which is also equivalent to 231 million pages of typed text. After 10 years, LSST is expected to have accumulated 15 to 20 petabytes or data, where one petabyte is 1,000 terabytes.
To manage the data flood, project researchers plan to dump the images and information into a database to be mined by individual astronomers searching for observations of specific objects.
"I think we're starting to understand that a lot of the important problems in astronomy we need to establish huge databases like this," said Sidney Wolff, an LSST board member. Wolff also heads the National Optical Astronomy Observatory's (NOAO) contribution to LSST's design. "
The NOAO represents the Association of Universities for Research in Astronomy (AURA) participation in LSST's development. The other groups include the Research Corporation, the University of Washington and the University of Arizona.
Design decisions
There are still some LSST decisions to be made before the project can proceed, among them deciding exactly which type of imaging technology to use in the telescope and determining a set location to build it.
Pinto told SPACE.com that a crucial decision lies in whether LSST's imaging system would use established CCD chips or the younger Complementary Metal Oxide Semiconductor (CMOS) technology. Project designers are still evaluating the pros and cons of both systems.
Project scientists are looking at regions of northern Chile, the Western deserts in the United States and Baja California, though a final location will be decided in upcoming months. A final LSST design should be in hand by later this fall, Wolff added.
http://www.space.com/businesstechnology/lsst_telescope_030730.html
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