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This article is from the Astronomy FAQ, by Joseph Lazio (jlazio@patriot.net) with numerous contributions by others.

64 Has anyone attempted to discern details of the star that went supernova and formed our local group of stars?

By Joseph Lazio <jlazio@patriot.net>

There's one reason, and possibly two, why this cannot be done.

First, our local group of stars is not the group of stars near the Sun
when it formed. All stars have some small random motion, in addition
to their general revolution about the center of the Milky Way Galaxy.
This random motion is typically 10 km/s. Moreover, in the solar
neighborhood, stars tend to have roughly the same velocity (~ 200
km/s), but stars slightly closer to the Galactic center have a smaller
orbit than stars slightly farther away from the Galactic center. The
combination of these factors means that, over the roughly 20 Galactic
orbits that the Sun has completed since it first began fusing hydrogen
in some molecular cloud, its sister stars have dispersed all over the
Galaxy. They are all probably at roughly the same distance from the
Galactic center as the Sun, but some might be on the other side of the
Galaxy by now.

Second, when referring to a supernova and the formation of the Sun,
most people have in mind the hypothesis that the solar system's
formation began as the result of a supernova shock wave impinging on a
molecular cloud. This hypothesis was proposed to account for the
presence of very short-lived isotopes in meteorites. For instance,
the decay products of Aluminum-26 have been found in meteorites. The
half-life of Al-26 is less than 1 million years. Thus, the hypothesis
asserts that, in order for any substantial amount of Al-26 to have
been incorporated into solar system meteorites, there must have been a
supernova (within which Al-26 can be made) quite close to the nascent
solar system.

This hypothesis is being challenged. Recent Chandra X-ray Observatory
observations have shown that young stars may be much more energetic
than the Sun is currently,
<URL:http://chandra.harvard.edu/press/01_releases/press_090601solar.html>.
If so, then it is possible that some of the X-ray flares produced by
the young Sun might have been enough to explain some or all of the
unusual isotopes found in meteorites. Thus, no supernova might be
required to explain the presence of the solar system.

Continue to:

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