Survey Nets Discoveries Far and Near
PASADENA, CA (JUNE 5, 2001) --
Casting a wide net on the sky, astronomers have brought in a bumper crop
of new discoveries. Their net is the Sloan Digital Sky Survey, or SDSS,
what astronomer Michael Turner called "one of the boldest undertakings
ever initiated in astronomy." Their quarry ranges from the most distant
known objects in the universe to objects within our own solar system.
Turner is a member of the SDSS team from the University of Chicago.
The survey is a project to map the entire sky, to provide "a field guide
to the heavens" for both astronomers and the public, Turner said. The
SDSS collaboration announced its first release of data at this week's
American Astronomical Society meeting. The release includes 500 square
degrees of sky, 500 gigabytes of images, precision measurements of about
14 million objects, and spectra of 50,000 galaxies and 5,000 quasars.
The survey will eventually catalogue more than 200 million objects.
The collaboration announced that it has just found the two most distant
objects in the universe, two quasars with redshifts of 6.2 and 6.0. So
far, the SDSS has found 13,000 quasars, and 26 of the 30 most distant
quasars known. The light from these quasars gives astronomers
information from the time when the universe, now between 10 and 15
billion years old, was only about 800 million years old. Decoding this
light will help astronomers to understand how galaxies formed very early
in the universe's evolution.
When the Sloan telescope is mapping the sky, looking at objects at the
very edge of the universe, it's inevitable that smaller nearby objects
-- like asteroids in our solar system -- wander across its field of
view. Astronomers had to figure out how to tell them apart from quasars,
because both show up as red objects in the survey images. According to
Tom Quinn, a member of the SDSS collaboration from the University of
Washington, "one man's contamination is another man's data." He is using
the asteroid "contamination" in the Sloan survey pictures to look at the
size and distribution of asteroids in the asteroid belt. Quinn said the
data help nail down the origin of the Near-Earth Asteroids, some of
which might be an impact threat to our planet.
Aside from finding interesting individual celestial objects, the survey
will have widespread uses in studies of cosmology, said Alex Szalay of
The Johns Hopkins University. The catalogue can be searched to create
statistically fair samples for use in cosmology research. The Sloan
survey marks the "transition into the era of high-precision cosmology,"
Szalay said.
The academics involved in the project are getting some help from the
private sector to bring the treasures discovered by Sloan to the general
public. Microsoft and Compaq are providing funds to create a website
where anyone can access the Sloan data. The project is currently in the
development stages.
The Sloan telescope is still mapping the heavens from its mountaintop
perch at Apache Point Observatory, near Sunspot, New Mexico. The survey
is funded by the Alfred P. Sloan Foundation, NASA, the National Science
Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho,
and the Max Planck Society.
Rebecca Johnson
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