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BLAST prepares for launch.
Photo Credit: Mark Halpern
The BLAST payload, at right, is readied for launch from the Long Duration Balloon facility near McMurdo Station in December 2006. The telescope found that half of the starlight of the universe comes from young, star-forming galaxies billions of light years away.

Starlight, starbright

BLAST knocks off the dust from distant galaxies to provide new view of the universe

After two years analyzing data from the Balloon-borne Large-Aperture Sub-millimeter Telescope (BLAST) External Non-U.S. government site project, an international group of astronomers and astrophysicists from the United States, Canada and the U.K. reported in the journal Nature this month that half of the starlight of the universe comes from young, star-forming galaxies several billion light years away.

Led by Mark Devlin External Non-U.S. government site, a professor of Astronomy and Astrophysics at the University of Pennsylvania External Non-U.S. government site, the scientists launched the two-ton telescope in December 2006 from near McMurdo Station External U.S. government site in Antarctica using a long-duration balloon that carried the instrument 39 kilometers above the Earth.

Flying the telescope above much of the atmosphere allowed the BLAST team to peer out into the distant universe at wavelengths nearly unattainable from the ground to help solve a mystery that began years ago.

In the 1990s, NASA’s COBE satellite External U.S. government site  discovered a nearly uniform glow of submillimeter light, known as the Far Infrared Background. Scientists believed this radiation was coming from warmed dust enshrouding bright young stars, but the nature of the galaxies that contain the dust had remained a mystery.

“Stars are born in clouds of gas and dust,” explained Barth Netterfield External Non-U.S. government site, a cosmologist in the Department of Astronomy & Astrophysics at University of Toronto External Non-U.S. government site. “The dust absorbs the starlight, hiding the young stars from view. The brightest stars in the universe are also the shortest lived, and many never leave their stellar nursery. However, the warmed dust emits light at far-infrared and submillimeter wavelengths — invisible to the human eye, but visible to the sensitive thermo-detectors on BLAST.”

The Nature study combines BLAST submillimeter observations at wavelengths around 0.3 millimeters — between infrared and microwave wavelengths — with data at much shorter infrared wavelengths from NASA’s Spitzer Space Telescope External U.S. government site to confirm that all of the Far Infrared Background comes from individual distant galaxies, answering a decade-old question of the radiation’s origin.

“For weeks in 2006 and early 2007, BLAST traveled over Antarctica making maps of the submillimeter sky,” said Devlin, the project’s principal investigator (PI). “We measured everything, from thousands of small clouds in our own galaxy undergoing star formation to galaxies in the universe when it was only a quarter of its present age.”

In one 11-day balloon flight, BLAST found more than 10 times the total number of submillimeter starburst galaxies detected in a decade of ground-based observations. The scientists say this “rich data set” is being mined for further information about these dust-enshrouded galaxies to lean more about their evolutionary history, any relationship with other galaxies, and associations with larger-scale structures in the universe.

“BLAST has given us a new view of the Universe,” said Netterfield, the Canadian PI for the project. “The data we collected enable us to make discoveries in topics ranging from the formation of stars to the evolution of distant galaxies.”

NSF-funded research in this story: Mark Devlin, University of Pennsylvania.