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By: Staff Reports
After two years analyzing data from the Balloon-borne
Large-Aperture Sub-millimeter Telescope (BLAST) 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 , a professor of Astronomy and Astrophysics
at the University of Pennsylvania , the scientists launched
the two-ton telescope in December 2006 from near McMurdo
Station 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 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 , a cosmologist in the Department
of Astronomy & Astrophysics at University of Toronto
. “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
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.”
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