From Mars landings to new theories explaining the birth of the universe, astrophysicists relish their newfound popularity on the front page. Astronomy's recent achievements are even more surprising considering that the discipline has made its advances without the most basic of tools: a map.
To remedy the problem, a group of astronomers from eight different universities and research institutions have come together to build a three-dimensional digital image of the universe - dubbed the Sloan Digital Sky Survey - using an advanced telescope constructed last month at the Apache Point Observatory in New Mexico. When it is completed, the map will be made available over the Internet.
To understand the scope and promise of the project, Alex Szalay, a professor of physics and astronomy at Johns Hopkins University and architect of the project's database component, points out that to date astronomers have mapped some 60 galaxies out of a pool of more than 100 million. Since the Sky Survey will enable astronomers to map the distances of six thousand galaxies a day, "in ten days we can exceed the combined knowledge of humanity," he said.
Until recently, astronomers couldn't build a telescope capable of measuring distances over the vast reaches of the universe, and a digital representation of the universe was impossible without using the latest advances in computing technology - especially the massive database parsing software. While other astronomy projects aim to answer many of the same questions that the Sky Survey addresses, observers say a map of the universe will be uniquely valuable.
"It's an example of what technology can do when it collects massive amounts of data. When you get enough of a quantitative change you get a qualitative change too - this will give us new knowledge on how the cosmos is put together. There's nothing duplicating this," says Alan MacRobert, an associate editor at Sky & Telescope magazine in Cambridge, Mass.
The key technology undergirding the new telescope is an array of charge-coupled devices, or CCDs, small silicon chips that convert incoming light to electrical signals. While the typical large telescope has at most a few CCDs in its focal plane, the Sky Survey telescope will contain fifty-four of the chips. Inside the telescope is an extremely sensitive camera able to detect the varying brightness of more than 100 million celestial objects as well as the spectra for about a million galaxies and 100,000 quasars.
The last attempt at a map of the universe was the Palomar Sky Survey, undertaken in the 1940s. The new Sky Survey will yield results in five colors compared to Palomar's two and its cameras will be some fifty times more powerful, promising the most comprehensive map for the next fifty years, predicted University of Washington astrophysicist Bruce Margon, the Survey's scientific director.
Capturing the data is only the first part of the mapping puzzle. Composing the data into an accessible three-dimensional map available on the Internet presents its own complexities. When completed, the Sky Survey is expected to take up some 40 terabytes of raw data. Uncompressed and unorganized, the data would currently take two years for a person using a desktop PC to download, according to Szalay of Johns Hopkins, who is using online analytical processing technology and also working with Microsoft's data mining division and a database company called Objectivity to solve the database access problem.
"We are going to put it on the Web and we're trying to figure out the best way of doing it. One way is to organize the data in chunks and write parallel software. We hope to build an engine with commodity components that can access the data," says Szalay.
Ultimately, says Tim Heckman, an astronomer at Johns Hopkins and one of the chief researchers involved in the project, the Sky Survey will lead to entirely unexpected scientific discoveries.
"It's not only an interesting project from the point of view of cartography, but the structure of the universe contains the important clues as to how the universe was created," says Heckman. "The data will be there, you will be able to make a straightforward query of the data, and do a lot of experiments at the push of a button right in your computer. I think that's sure to lead to a lot of unanticipated discoveries."
In addition to Johns Hopkins and the University of Washington, the other institutions participating in the Sky Survey include University of Chicago, Fermilab, The Institute for Advanced Study, Japan Participation Group, U.S. Naval Observatory, Princeton University, and Apache Point Observatory.
