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GOURDHEAD
2005-Mar-02, 03:17 PM
Here (http://www.spitzer.caltech.edu/Media/releases/ssc2005-08/release.shtml) is a story about early galaxy sizes and contents. If that much silicate was present, there must have been lotsa CHON, so earthlike planets must have been around much longer than I have previously thought. When stars form out of material that rich in "metals", do they behave differently from those formed from only hydrogen and helium?

Here (http://story.news.yahoo.com/news?tmpl=story&cid=96&ncid=96&e=2&u=/space/20050301/sc_space/unknownforcetriggersstarformation) is a story about star formation.

Erimus
2005-Mar-02, 06:26 PM
<<When stars form out of material that rich in "metals", do they behave differently from those formed from only hydrogen and helium?>>

Though I&#39;m no expert, my understanding of star formation is that it does, in two ways:

1.) Metal-rich clouds radiate their heat more efficiently, making it easier for them to collapse to form stars.

2.) Metal-rich stars are cooler and larger for a given mass than metal-poor ones. Metals increase the "opacity" of a star&#39;s outer layers, making it less transparent to its own radiation, thus causing it to reach equilibrium at a larger size and cooler temperature--but at the same luminosity as a metal-poor star of the same mass. If our Sun were very metal-poor, it would probably have a spectral well into the F range, but it would be no more brighter.

There&#39;s a lot of material out there on stars like this (metal-poor stars that are "too dim" for their spectral type), which are known as subdwarfs.