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"Long
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April 29, 2009
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A brighter universe found: ours
May 16, 2008
Courtesy Science & Technology
Facilities Council, U.K.
and World Science staff
The Universe is twice as bright as previously
believed: dust turns out to block about half the starlight from us, astronomers have
found. The dusty galaxy NGC 4565
(Courtesy Robert Gendler)
“Interstellar dust grains have a devastating effect on our measurements of the energy output from even nearby galaxies,” said Richard Tuffs of the Max Plank Institute for Nuclear Physics in Heidelberg, Germany, one of the researchers.
Astronomers have long known there’s dust out there, but didn’t know how much this restricts the light we can
see. The dust itself glows, because it absorbs and then re-emits starlight.
Something “very wrong” has afflicted past theories touching on the issue, said Simon Driver of the University of St Andrews, U.K., lead author of
a report on the findings. The previous models, he continued, show the glowing dust’s energy output as greater than the stars’ total energy, which is impossible.
His team assembled a high-resolution catalogue of 10,000 galaxies and analyzed it together with a new model of galactic dust distribution developed by Tuffs and Cristina
Popescu of the University of Central Lancashire, U.K.
With the new model, the astronomers said they could calculate the precise fraction of starlight blocked. The absorbed starlight energy finally
equalled that detected from the glowing dust, as makes sense, they said.
“For the first time we have a total understanding of the energy output of the Universe over a monumental wavelength [light energy] range,” said
Popescu. (Scientists use the term “light” to include not just visible
light but also the forms that are invisible to the eye because their
energy is lower or higher than than what we naturally see.)
The team measured cosmic energy per cubic light-year—a cube with each side’s length the distance light moves in a year. Within such a space, the Universe generates some five quadrillion Watts yearly on average, about 300 times the energy consumption of Earth’s population, the researchers said.
The findings appear in the May 10 issue of the research publication
Astrophysical Journal Letters.
The team measured the brightness of thousands of disc-shaped galaxies with different orientations, then matched the results to computer models of dusty galaxies. Based on this they calibrated the models to find out how much light is blocked when a galaxy is seen face-on. This in turn let them determine the fraction of galactic light that escapes in each direction.
“For over 70 years an accurate description of how galaxies—the locations where matter is churned into energy—form and evolve has eluded
us,” said Driver. “Balancing the cosmic ‘energy budget’ is an important step forward.”
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The Universe is twice as bright as previously thought: dust turns out to block about half the starlight from our view, astronomers have found. “Interstellar dust grains have a devastating effect on our measurements of the energy output from even nearby galaxies” said Richard Tuffs of the Max Plank Institute for Nuclear Physics in Heidelberg, Germany, one of the researchers. Astronomers have long known there’s dust out there, but didn’t know how much this restricts the light we can see. The dust itself glows, because it absorbs and then re-emits starlight. Something “very wrong” has afflicted past theories touching on the issue, said Simon Driver of the University of St Andrews, U.K., lead author of the report on the new findings. The previous models, he continued, show the glowing dust’s energy output as greater than the stars’ total energy, which is impossible. His team assembled a high-resolution catalogue of 10,000 galaxies and analyzed it together with a new model of galactic dust distribution developed by Tuffs and Cristina Popescu of the University of Central Lancashire, U.K. With the new model, the astronomers said they could calculate the precise fraction of starlight blocked. The absorbed starlight energy finally equalled that detected from the glowing dust, as makes sense, they said. “For the first time we have a total understanding of the energy output of the Universe over a monumental wavelength [light energy] range,” said Popescu. The team measured cosmic energy per cubic light-year, a cube with each side’s length the distance light moves in a year. Within such a space, the Universe generates some five quadrillion Watts yearly on average, about 300 times the energy consumption of Earth’s population, the researchers said. The findings appear in the May 10 issue of the research publication Astrophysical Journal Letters. The team measured the brightness of thousands of disc-shaped galaxies with different orientations, then matched the results to computer models of dusty galaxies. Based on this they calibrated the models to find out how much light is blocked when a galaxy is seen face-on. This in turn let them determine the fraction of galactic light that escapes in each direction. “For over 70 years an accurate description of how galaxies, the locations where matter is churned into energy, form and evolve has eluded us. Balancing the cosmic energy budget is an important step forward,” said Driver.