Lights of universe are fading, British astronomers report

Studies show old stars are dying faster than new ones are forming

August 23, 2003|By KNIGHT RIDDER/TRIBUNE

WASHINGTON - As if we didn't have enough troubles here on Earth, there's disturbing news from outer space. Reports just in from American and European astronomers warn that:

The universe is fading, as old stars burn out faster than new ones are born.

A huge storm of stardust is heading for our solar system.

Fortunately, astronomers say neither of these far-off developments poses any immediate danger to people on Earth. You have time to pay off the mortgage.

The stardust, however, could build up on the solar panels of spaceships, including the International Space Station, causing a gradual loss of power. Telescopes studying other planets will have to peer through a thicker haze of dust.

The warning about the shrinking star population came in a report published by the Royal Astronomical Society of Great Britain this week. Its title: "Dim Future for the Universe as Stellar Lights Go Out."

Astronomers have known for decades that trillions of years from now all the stars will have used up their hydrogen fuel, galaxies will wink out and the universe will go dark.

What's new in the British report is evidence confirming that the star count is already dropping. New data from a survey of 40,000 galaxies show that the heavenly population began to shrink about 6 billion years ago, more than a billion years before Earth took shape.

"The process of galaxy formation had its heyday some time ago," the lead author of the report, the aptly named Alan Heavens, a professor of astronomy at the University of Edinburgh, Scotland, said in an e-mail message.

"The number of new stars being formed in the huge sample of galaxies we studied has been in decline for around 6 billion years, roughly since the time our own sun came into being," he said. "The age of star formation is drawing to a close."

To track the downward trend in the star census, Heavens and a colleague, Raul Jimenez, an astrophysicist at the University of Pennsylvania, studied what they called the "fossil record" of star births and deaths hidden in starlight.

Young stars tend to be hot and shine with a bluish light. Older stars are cool and reddish.

Stars are born from vast clouds of gas, mostly hydrogen and helium. As the universe grows older, however, it's using up its supply of gas, slowing the rate of star formation.

"The universe is running out of gas," Fred Adams, an astrophysicist at the University of Michigan, Ann Arbor, said in an e-mail message.

Adams, who isn't part of the Heavens-Jimenez research team but agrees with its findings, said the Milky Way would deplete its gas reserves in about 10 billion years.

"When the universe is 100 trillion years old, essentially all of the conventional star formation in galaxies will grind to a halt," he predicted in his book The Five Ages of the Universe.

The heads-up about a cosmic dust storm came this week from Markus Landgraf, a physicist at the European Space Agency in Darmstadt, Germany. An American-European spaceship named Ulysses, which has been monitoring the gentle rain of particles from outer space since 1990, provided the evidence.

Stardust consists of tiny grains of elements such as carbon, silicon, oxygen and iron, each about one-hundredth the width of a human hair. The dust is produced when dying stars blow up and fling their ashes into interstellar space.

Normally, the sun's powerful magnetic field keeps most of the dust grains outside the solar system. Only about one grain per cubic kilometer - equal to a box about six-tenths of a mile on each side - slips through.

Starting in 2000, however, a change in the sun's magnetism will let the flow increase to three or four particles per cubic kilometer. Landgraf said another threefold rise was on its way.

"After 2005 we expect a level 10 times above the dust concentration measured in the mid-1990s," he said.

"Interstellar dust is not a hazard to life on Earth," Landgraf added.

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