>From: Tom Coulter <email@example.com>
>Subject: dicklit: A Violent Blast Of Radiation Spawned The Planets (fwd)
>Claire Bowles, firstname.lastname@example.org, 44-171-331-2751
>New Scientist Washington office, email@example.com, 202-452-1178
>EMBARGOED FOR RELEASE: September 8, 1999, 2 p.m. EDT
>A violent blast of radiation spawned the planets
>The formation of the Solar System was hurried along by a nearby gamma-
>ray burst, two astrophysicists in Ireland suspect. Rather than aborting
>the birth of planets, the flood of energy may have melted primordial
>dust grains, seeded the formation of meteorites and helped form the
>rocky planets, including Earth.
>For over a century, astronomers have tried to understand what made
>clumps of dust circling the young Sun melt into chondrules-rocky
>beads rich in iron and silicon minerals that make up the bulk of stony
>meteorites. Suggestions included shock waves and gigantic flashes of
>Now Brian McBreen and Lorraine Hanlon of University College Dublin
>suggest that all the chondrules in the Solar System formed in a matter
>of minutes 4.5 billion years ago when a gamma-ray burst-one of the
>most powerful explosions in the Universe-seared the dust and gas
>circling the Sun with intense X-rays and gamma rays. Astronomers
>aren't sure what causes gamma-ray bursts, but they may occur when
>supermassive stars explode at the end of their lives (New Scientist,
>3 April, p 5).
>In a paper that will appear in a future issue of Astronomy and
>Astrophysics, McBreen and Hanlon calculate that a gamma-ray burst
>within 300 light years would have flooded the dusty disc circling the
>young Sun with enough energy to fuse up to 100 Earth masses of material
>into droplets that cooled into chondrules. These, and the dust from which
>they formed, are rich in iron, which would have soaked up X-rays and
>gamma rays very efficiently. "It explains the key role played by iron,
>which dominates the X-ray and gamma-ray absorption," says McBreen.
>If the theory is right, it makes the Solar System more unique than many
>scientists would like. McBreen and Hanlon believe that only one Sun-like
>star in a thousand would have been close enough to a gamma-ray burst
>to form chondrules. Because they also think that the dense chondrules
>settle quickly into the plane of a protoplanetary disc and speed the
>formation of planets, their theory implies that solar systems such as
>ours are rare.
>"Forming chondrules really is a long-standing problem, so if this
>mechanism accounts for them, that would be pretty fantastic," says
>Alan Boss, an astrophysicist at the Carnegie Institution in Washington
>DC. Still, he is reluctant to rely on an unlikely event as a crucial factor
>in the formation of the Solar System, and wonders whether the idea can
>explain other features of chondrules, such as their size and abundance.
>"I don't think you'd want to invoke it unless it takes care of everything,"
>Specialists in meteorites are intrigued by McBreen's idea. "Chondrule
>formation remains a thorny subject, so it's good to see a new idea in
>the area," says Ian Wright, a meteoriticist at the Open University in
>London. He notes that most of the researchers studying meteorites
>believe chondrules did not form all at once, although the case is not
>closed. "It will certainly cause debate, and it's an interesting idea
>that can be tested in our labs."
>Author: Robert Adler
>New Scientist issue 11th September 99
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