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Old April 23 2013, 01:24 AM   #9
Christopher
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Re: NASA finds more planets that could support life!

The galactic stellar disk is considered to have a radius of c. 50,000 light years. The Sun is about 27,000 ly from the center. So we're just beyond halfway out. That's what I mean by "the middle of the galactic disk," which was a poor choice of words. I tend to think of the stellar disk (not counting the central bulge) as consisting of three concentric regions, inner, middle, and outer. We're in the middle region, which is often called the "Galactic Habitable Zone" but which I think could more properly be called the temperate zone. As stated, it's likely to have a higher percentage of life-bearing planets than the inner region (with the hazards I mentioned above) or the outer one (where the stellar metallicity is lower and planets may be less common), but again, the number of stars in the inner region is great enough that there would probably still be more habitable worlds there.
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