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The Whole Sky: Pretty Pictures, Hard Data from 6-Year Mapping Project
By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
08 April 2003
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www A diverse and comprehensive array of photographs from the world's first near-infrared all-sky survey has been released for professional and amateur astronomers to explore and study. The mapping project, called the Two Micron All-Sky Survey, imaged the whole sky with a pair of little-known 51-inch (1.3-meter) telescopes, one at Mount Hopkins in Arizona the other at the Cerro Tololo Inter-American Observatory in Chile. The result is a remarkable gallery of near-infrared light images, which involve wavelengths of light just outside what can be seen with the human eye and optical telescopes. The project began in 1997 and was only recently completed. Now the wealth of data and imagery has been put online so any astronomer can attempt to make new discoveries. The 2Mass archive, as it's known, has already contributed important findings, such as confirming the existence of failed stars known as brown dwarfs, but it is expected to yield many more findings now that the data is available to all. Near-infrared observations reveal intrinsically dim stars and objects whose visible light is obscured by dust, explained Martin Weinberg, a 2Mass scientist at the University of Massachusetts at Amherst, where the project is based. Infrared radiation penetrates through most dust, which surrounds many stars and permeates galaxies. "Current understanding of galaxy properties has been strongly biased by the small fraction of hot, young stars that make up much of what we observe in optical-wavelength surveys," Weinberg told SPACE.com. "I anticipate that 2MASS will help answer key questions about local galaxy properties and their distribution." The completed 2Mass catalogue contains 10 terabytes of information in 4 million separate images. On the digital photographs are some 471 million objects that have been identified as mostly stars (some are comets and asteroids that await discovery). An additional 1.6 million objects have been catalogued separately as probable galaxies. | Gallery of 2Mass Images | | Among the 2Mass images (clockwise from top left): the Keyhole Nebula; our Galactic Center; and the whole Milky Way. Gallery >>> | | | | Weinberg invoked political polling as a way to explain why such a comprehensive survey is an important complement to images of specific objects obtained by more celebrated observatories, such as the Hubble Space Telescope. "Conclusions drawn from people in one specific neighborhood in a single city (say 300 people) are likely to be different than a national census of millions of people," he said. "Similarly, if my goal is to study the large-scale structure of the Milky Way Galaxy or the large-scale distribution of galaxies in the universe, I need to sample the galaxy or universe in all directions or run the risk of a biased result owing to the choice of a particular direction or set of directions." Still, 2Mass is just one survey. The stars it reveals are only about one-half of 1 percent of the total stars in the Milky Way. Which means that while astronomers mine 2Mass for years to come, there is plenty of room for more fresh observational work, too.
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