T Tauri: a young
stellar object
    HII regions Sharpless

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Contact: Jane Platt



       A colossal assortment of star-studded, galaxy-filled pictures and information - enough to fill the hard disks on hundreds of home computers - is contained in the first major data release from a telescope sky survey sponsored by NASA and the National Science Foundation.

       "We've posted a cornucopia of images on the Internet for average home computer users as well as professional astronomers," said Dr. Michael Skrutskie, principal investigator of the survey, designed to catalog 1 million galaxies, 300 million stars, and other celestial objects. The collection includes up-and-comers like T Tauri, an infant star, and stellar has-beens like the Crab Nebula (the remnant of an exploding former star).

       This early data sampling includes 230,000 pictures derived from 3 million raw images, taken by a pair of 1.3-meter (51-inch) telescopes near Tucson, AZ, and at Cerro Tololo, Chile. This first sample represents just 6 percent of the anticipated final database of the Two-Micron All-Sky Survey (2MASS). The telescopes study near-infrared wavelengths not visible to the naked eye. By sensing heat, they detect heat-emitting objects like stars and galaxies that hide behind curtains of cold dust throughout our Milky Way galaxy.

       "Because the Milky Way is very dusty, we know very little about how it's put together. It's like living in a city where there's a constant dust storm and you have no idea what roads, mountains and buildings are beyond your own house," Skrutskie said. "Our sky survey helps us see through the dust to get a clearer view of the Milky Way."

       "We live inside the Milky Way Galaxy, which is shaped like a flattened disk with embedded gas and dust," explained Dr. Roc Cutri, 2MASS project scientist. "With visible light, dust limits our view along the flattened disk. But near-infrared light is less affected by dust, exposing many galaxies outside the Milky Way that would otherwise be hidden."

       2MASS, based at the University of Massachusetts, Amherst, where Skrutskie is a physics and astronomy professor, is two years into a three-and-a-half year survey of the entire sky.

       One of the survey's most significant findings is the definition of a class of stars called L-dwarfs, the coolest stars known. "It's the first new classification of this type in nearly a century," Cutri said. "We knew L-dwarfs existed, but 2MASS established the category definitively. These may be the most common stars in our galaxy or maybe the universe."

       Cutri is affiliated with the JPL/Caltech Infrared Processing and Analysis Center, which combines and processes 2MASS images into usable data. The raw, unprocessed data contained in this current batch fills more than one terabyte, or 1,000 gigabytes, of computer memory. The average home computer contains less than 10 gigabytes of storage. Thanks to the Internet, people can browse individual pictures without downloading the entire database and gobbling up their computer memory.

       Additional releases are planned every six months through the end of 2000. With these images and catalogs, astronomers can pinpoint positions and brightness of stars and other objects, and determine sizes and shapes of galaxies and nebulae. They can then choose specific objects for further study.

       "We count the dots, so to speak, to study how galaxies are scattered in the nearby universe," Skrutskie said. "The texture of this distribution echoes how material was hurled about and eventually settled into galaxies and stars after the Big Bang."

       2MASS, part of NASA's Origins Program, is funded by NASA's Office of Space Science and the National Science Foundation. 2MASS results will benefit future Origins missions, including Space Infrared Telescope Facility and the Next Generation Space Telescope. JPL manages the program for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA.

       The current data release is available at the following website:

       http://www.ipac.caltech.edu/2mass/gallery/spr99/ Additional 2MASS information and images are available at the following websites:


5/7/99 JP