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 BBC NEWS
Meteorite gives clues to Sun birth
*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.

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.

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/4205227.stm

Published: 2005/01/25 13:13:04 GMT