Taking cartography to a new level, faculty in the UW Department of Astronomy are key players in an ambitious new effort to create the first-ever digital map of the heavens.

The project, known as the Sloan Digital Sky Survey, involves gathering astronomical data and using it to create a three-dimensional map of the universe, as it is seen from the Northern Hemisphere.

In June the survey's first data were captured using a new telescope at Apache Point Observatory in New Mexico. "It was incredible to see such a large piece of the sky presented in such depth and fine detail--really a beautiful sight," said one observer.

"This will be an encyclopedia of the sky, so the possible projects resulting from the information are never-ending."

Much of the state-of-the-art equipment created for the survey was designed by UW scientists, including the telescope; the optics, including the telescope's primary and secondary mirrors; and parts of the spectroscopic systems, which will disperse light into its component colors, allowing for chemical analysis and distance measurements. UW scientists also designed the specialized buildings in which the equipment is housed.

Although it will take five years to gather all the data necessary for the map, data collected along the way will be made available to scientists and the general public.

"This will be an encyclopedia of the sky, so the possible projects resulting from the information are never-ending," says Bruce Margon, professor of astronomy and the project's scientific director.

Margon describes the Sloan survey as "a grand, challenging project" that will peer one billion light years into space. A light year equals 5.9 trillion miles.

"It will be significantly more sensitive than our current comprehensive guide to the heavens, the 40-year--old Palomar Sky Survey," says Margon. "The Palomar survey used photographic plates to produce two-color, two-dimensional images. Our survey will use digital technology and spectroscopy to produce five-color images in three dimensions. It will map one quarter of the sky and give us a three--dimensional picture of the universe through a volume one hundred times greater than anyone has explored before."

The survey is expected to find 500 million galaxies and a slightly larger number of stars, accurately chart their positions, and determine the brightness and color of each. Full spectral data of some one million galaxies and about 100,000 quasars also are expected.

Although the Sloan Survey will produce a huge volume of data, it still will cover just a small fraction of the universe. Margon does not consider this a problem. He explains that making a map from this information is something akin to political polling, if the statistics of the sample are well understood. "It's OK to survey a little corner of the universe and make conclusions about the whole universe, and that's what Sloan will do," he says.

Margon likens the survey to another major scientific undertaking--the teams of scientists trying to map billions of units of human DNA. "It should be viewed on the same scale as the human genome project, and it will produce more information," he says.

[Autumn 1998 - Table of Contents]