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Last Updated: Tuesday, 25 January, 2005, 13:13 GMT
Meteorite gives clues to Sun birth
Triffid Nebula, Nasa/HST/Jeff Hester
Our Solar System could have formed in a violent nebula
New meteorite data lends support to a controversial theory that the violent explosion of a star was involved in the creation of the Sun and its planets.

The primitive space rock contains signs that a short-lived, radioactive form of the element chlorine may have been present in the early Solar System.

A US-Chinese team claims the most likely source of this isotope was a supernova - or exploding star.

The findings appear in Proceedings of the National Academy of Sciences.

For years, astronomers have believed that the Solar System formed inconspicuously, from a slowly condensing cloud of dust and gas; but this traditional view is now being challenged.

The new theory proposes that our star and its planetary system were born in a dense interstellar cloud, or nebula, filled with short-lived, massive stars that exploded with immense energy and an intense release of radiation.

Supernovae occur at the end of a star's lifetime, when its nuclear fuel is exhausted and it is no longer supported by the release of nuclear energy.

Ancient relic

Researchers from Arizona State University and the Chinese Academy of Sciences studied a primitive meteorite from China known as the Ningqiang carbonaceous chondrite.

This space relic formed shortly after the creation of the Solar System. The team found a rare isotope of sulphur - sulphur-36 - in the meteorite, which can be produced through the radioactive decay of a form of chlorine called chlorine-36.

Because the sulphur isotope was found in an ancient mineral "inclusion" in the meteorite called sodalite, the researchers believe chlorine-36 could have been present in the early Solar System.

Supernova 1987A   Nasa/P. Challis/r. Kirshner/B. Sugerman
Supernovae can occur when stars reach the end of their lives
Chlorine-36 can form in two ways: by a supernova explosion, or by a nebular cloud being bombarded by radiation near the forming Sun.

The researchers consider the latter explanation is unlikely since sodalite must have formed some distance away from our star.

"There is no ancient live chlorine-36 in the Solar System now," said co-author Laurie Leshin, director of Arizona State's Center for Meteorite Studies. But this is direct evidence that it was here in the early Solar System."

Dr Leshin and others had previously found evidence for another radioactive isotope (or radionuclide) in the early Solar System called iron-60, which could also have been formed in a supernova.

"It's producing a really strong argument that these radionuclides were produced in a supernova that exploded near the forming Solar System and seeded [it] with these isotopes," Dr Leshin added.

If the controversial theory is supported by future work, it may have implications for understanding properties such as the size and shape of the Solar System, the physical make-up of the Earth and the chemistry that led to life.

Swift catches first cosmic blasts
07 Jan 05 |  Science/Nature
Supernova produces cosmic rays
04 Nov 04 |  Science/Nature
Hubble chases exploding stars
01 Oct 03 |  Science/Nature
Exploding star hunters make history
16 Sep 03 |  Science/Nature
Astronomers predict stellar explosion
16 Apr 03 |  Science/Nature

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