Dec. 12, 2007 -- The largest-ever three-dimensional survey of the Milky Way has just been released, listing more than 200 million objects in our home galaxy. The digital survey is already leading to discoveries about where in the sky stars are being born, as well as the relative numbers of different sorts of stars -- the galactic stellar demographics, if you will.
All the information is expected to help astronomers better understand the evolution of stars of all sorts, including our own, and improve our understanding of the layout of the Milky Way.
The survey was accomplished with one telescope on La Palma Islands in the Canaries, which looked at the galaxy entirely by the red light given off by hydrogen atoms. The "hydrogen-alpha" emissions reveal not only where the hottest stars are, but the stunning clouds of gas out of which they are created.
"Hot stars light up in these emission lines," said astronomer Nicholas Walton of the Institute of Astronomy at the University of Cambridge in the U.K.
Hot stars generally include those being born as well as those dying and shrinking into white dwarfs, he explained. So the hydrogen survey is helping sort out the locations of the Milky Way's stellar nurseries and old-age homes.
The hydrogen survey differs from the better known Sloan Digital Sky Survey (SDSS) in that it concentrates on the Milky Way, Walton said. The SDSS, on the other hand, avoids the Milky Way and focuses on the larger structures in the universe in other bands of light.
"They are very complimentary surveys," Walton told Discovery News.
Eventually, with technology already being planned, the distances of all those objects will be accurately mapped as well, allowing astronomers to create a three-dimensional map of the Milky Way with unprecedented detail.
"We will be able to see gravitational waves setting off star formation," as those waves roll through the galactic disk, Walton said.
For now, the next step is to finish the Milky Way survey with another telescope in the Southern Hemisphere, Walton said. A survey telescope at the Very Large Telescope in Chile will be used for that and is expected to add another 600 million objects to the survey, he said.
"I think these surveys are incredibly important," said astronomer Ed Churchwell of the University of Wisconsin in Madison. Churchwell was involved in a more detailed infrared survey of a smaller part of the Milky Way using NASA's Spitzer Space Telescope.
Surveys not only stumble onto things no one ever thought to look for, said Churchwell, they also put together large pieces of the sky and reveal larger structures. "You see things that you might not have otherwise seen at all. It's very easy to miss something very big."
The massive amounts of data generated by the surveys also create public archives of stellar information which can be mined for decades by other researchers, Churchwell said.
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