Biggest picture of the sky unveiled

M. Blanton / SDSS III

The Sloan Digital Sky Survey III’s image of the night sky allows for a zoom-in view focusing in on the galaxy M33 (top left and top middle), and then on the star-forming region NGC 604. Click for a bigger version of the picture.

This video visualizes all of the imaging data for SDSS III Data Release 8.

Astronomers have assembled the biggest picture of the night sky ever made, marking the climax of an 11-year survey — and the picture will be soon be coming to a computer near you.

The Sloan Digital Sky Survey’s latest, greatest “picture” is actually a mosaic made from millions of telescope images, amounting to 1.2 trillion pixels in all. You’d need to spread the image out on 500,000 high-definition TVs to see the whole thing at full resolution. But that’s not really the point: The SDSS III image is a high-resolution, zoomable database for professional astronomers as well as the general public.

Previous SDSS imagery has served as a foundation for online planetarium programs such as Google Sky and Microsoft’s WorldWide Telescope. ( is a Microsoft-NBC Universal joint venture.) It’s also the database used by thousands of Galaxy Zoo citizen scientists to look for galactic curiosities such as Hanny’s Voorwerp, which is featured this week in a new Hubble image. The SDSS III imagery will likely be incorporated into all those user-friendly sky databases.

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The survey’s scientific mission In addition, researchers will be analyzing the pictures to study how our Milky Way is stealing stars from passing galaxies, how the distant universe is structured and whether the mysterious cosmic speed-up factor known as dark energy has changed over time.

“This is one of the biggest bounties in the history of science,” New York University astronomer Mike Blanton, who is leading the data archive work in SDSS III, said in today’s announcement of the image’s release.

The SDSS III archive should serve as a “unique reference for the next decade or longer,” he told journalists at the American Astronomical Society’s meeting in Seattle.

The Sloan Digital Sky Survey began in 1998, using what was then the world’s largest digital camera: a 138-megapixel imaging detector on the back of a dedicated 2.5-meter telescope at the Apache Point Observatory in New Mexico. Now, this imaging camera is being retired and will become part of the permanent collection at the Smithsonian, in recognition of its contributions to astronomy.

“This release really completes the mission of the SDSS camera that’s been going on for 11 years,” Blanton said. However, the SDSS III program will continue through at least 2014 with a more up-to-date array of instruments attached to the pre-existing telescope.

The future of sky surveys One of the SDSS projects is known as the Baryon Oscillation Spectroscopic Survey, or BOSS.

“We have upgraded the existing SDSS instruments, and we are using them to measure distances to over a million galaxies detected in this image,” said BOSS principal investigator David Schlegel, an astronomer from Lawrence Berkeley National Laboratory.

Schegel said that measuring the distances to galaxies will be more time-consuming than simply taking their pictures, but the exercise should result in a the world’s most detailed three-dimensional map of the galaxies’ distribution in space.

BOSS’ goal is to measure the effects of dark energy over the recent history of the universe to an accuracy of 1 percent. “Dark energy is the biggest conundrum facing science today,” Schlegel said in today’s announcement, “and the SDSS continues to lead the way in trying to figure out what the heck it is.”

Another survey, known as SEGUE, has used the SDSS imagery to analyze the distribution of stars on the edges of our own galaxy. “We have found many streams of stars that originally belonged to other galaxies that were torn apart by the gravity of our Milky Way,” said Connie Rockosi, an astronomer at the University of California at Santa Cruz who serves as SEGUE’s principal investigator.

Further study should provide “a more complex picture of how our galaxy grew,” she told journalists in Seattle.

SDSS III is planning two other surveys over the next four years: MARVELS will use a new instrument to measure the spectra for about 8,500 nearby stars like our own sun, looking for the telltale wobbles caused by Jupiter-scale planets that may be orbiting them. MARVELS is expected to detect about 100 giant planets plus a similar number of the failed stars known as brown dwarfs. The other survey, APOGEE, will conduct a spectroscopic study of stars in all parts of our galaxy.

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