Top Document: [sci.astro] Solar System (Astronomy Frequently Asked Questions) (5/9) Previous Document: E.01 How did the solar system form? Next Document: E.03 What is the "Solar Neutrino Problem?" See reader questions & answers on this topic! - Help others by sharing your knowledge Author: 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. User Contributions:Top Document: [sci.astro] Solar System (Astronomy Frequently Asked Questions) (5/9) Previous Document: E.01 How did the solar system form? Next Document: E.03 What is the "Solar Neutrino Problem?" Part0 - Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jlazio@patriot.net
Last Update March 27 2014 @ 02:11 PM
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