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November 08, 2012
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“Boom times” in star birth gone, never to return, study suggests
Nov. 8, 2012
Courtesy of the Royal Astronomical Society
and World
Science staff
While parts of the world
suffer economic hardship, astronomers have found an even bigger slump
under way on a cosmic scale: formation of new stars has crashed, perhaps permanently. This diagram indicates the changing ‘GDP’ of the Universe over time. The new results indicate that, measured by mass, the production rate of stars has dropped by 97 percent since its peak 11 billion years ago.
(Credit: D. Sobral)
“You might say that the universe has been suffering from a long, serious ‘crisis:’ cosmic GDP output is now only 3 percent of what it used to be at the peak in star production!” said David Sobral of the University of Leiden in the Netherlands.
“If the measured decline continues, then no more than 5 percent more stars will form over the remaining history of the cosmos, even if we wait forever. The research suggests that we live in a universe dominated by old stars.”
In the largest ever study of its kind, the international team of astronomers has concluded that the rate of formation of new stars in the Universe is now only 1/30th of its peak. The group, led by Sobral, is reporting its results in the journal
Monthly Notices of the Royal Astronomical Society.
The most accepted model for the evolution of the Universe predicts that stars began to form about 13.4 billion years ago, or around
300 million years after the its birth. Many of these first stars are thought to have been monsters by today’s standards, and were probably hundreds of times more massive than our Sun. Such beasts would have aged very quickly, exhausted their fuel, and exploded within a million years or so. Lighter stars in contrast live much longer, for billions of years.
Much of the dust and gas from stellar explosions was (and is still) recycled to form newer generations of stars, astronomers say. Our Sun, for example, is thought to be a third generation star, and has a typical mass, or weight, by today’s standards. But regardless of their properties, stars are key ingredients of galaxies like our own Milky Way. Scientists say unveiling the history of star formation is fundamental to understanding how galaxies form and evolve.
In the study, astronomers used the U.K. Infrared Telescope, the Very Large Telescope and the Subaru telescope to carry out what they called the most complete survey ever made of star-forming galaxies at different distances, with around ten times the data of any previous effort. With the range of distances, the time taken for the light to reach us means that we see identically selected galaxies at different periods in the history of the universe, they said, so we can really understand how conditions change over time.
By looking at the light from clouds of gas and dust in these galaxies where stars are forming, the team estimated the rate at which stars are being born. They found that the production of stars has been continuously declining over the last 11 billion years, being 30 times lower today than at its likely peak, 11 billion years ago.
“Half of these were born in the ‘boom’ that took place between 11 and 9 billion years ago and it took more than five times as long to produce the rest,” Sobral said. “The future may seem rather dark, but we’re actually quite lucky to be living in a healthy, star-forming galaxy which is going to be a strong contributor to the new stars that will form.
“Moreover, while these measurements provide a sharp picture of the decline of star-formation in the Universe, they also provide ideal samples to unveil an even more fundamental mystery which is yet to be solved: why?”
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While parts of the world undergo economic hardship, astronomers have found an even bigger slump happening on a cosmic scale: formation of new stars has crashed, perhaps permanently. “You might say that the universe has been suffering from a long, serious ‘crisis:’ cosmic GDP output is now only 3% of what it used to be at the peak in star production!” said David Sobral of the University of Leiden in the Netherlands. “If the measured decline continues, then no more than 5% more stars will form over the remaining history of the cosmos, even if we wait forever. The research suggests that we live in a universe dominated by old stars.” In the largest ever study of its kind, the international team of astronomers has concluded that the rate of formation of new stars in the Universe is now only 1/30th of its peak. The group, led by Sobral, is reporting its results in the journal Monthly Notices of the Royal Astronomical Society. The most accepted model for the evolution of the Universe predicts that stars began to form about 13.4 billion years ago, or around three hundred million years after the Big Bang. Many of these first stars are thought to have been monsters by today’s standards, and were probably hundreds of times more massive than our Sun. Such beasts would have aged very quickly, exhausted their fuel, and exploded within a million years or so. Lighter stars in contrast live much longer, for billions of years. Much of the dust and gas from stellar explosions was (and is still) recycled to form newer and newer generations of stars, astronomers say. Our Sun, for example, is thought to be a third generation star, and has a typical mass, or weight, by today’s standards. But regardless of their properties, stars are key ingredients of galaxies like our own Milky Way. Scientists say unveiling the history of star formation is fundamental to understanding how galaxies form and evolve. In the study, astronomers used the U.K. Infrared Telescope, the Very Large Telescope and the Subaru telescope to carry out what they called the most complete survey ever made of star-forming galaxies at different distances, with around ten times the data of any previous effort. With the range of distances, the time taken for the light to reach us means that we see identically selected galaxies at different periods in the history of the universe, they said, so we can really understand how conditions change over time. By looking at the light from clouds of gas and dust in these galaxies where stars are forming, the team estimated the rate at which stars are being born. They found that the production of stars in the universe as a whole has been continuously declining over the last 11 billion years, being 30 times lower today than at its likely peak, 11 billion years ago. “Half of these were born in the ‘boom’ that took place between 11 and 9 billion years ago and it took more than five times as long to produce the rest,” Sobral said. “The future may seem rather dark, but we’re actually quite lucky to be living in a healthy, star-forming galaxy which is going to be a strong contributor to the new stars that will form. ‘Moreover, while these measurements provide a sharp picture of the decline of star-formation in the Universe, they also provide ideal samples to unveil an even more fundamental mystery which is yet to be solved: why?”