Hubble Ultra-Deep Field Image

I think the Hubble UDF/XDF is probably one of the most interesting images in astronomy ... in short, every one of those dots/blobs is an entire galaxy, each with (on average) in the order of hundreds of millions of stars ... and the staggering part is that this image shows only an extremely tiny portion of our sky (much smaller than the visual area the Moon occupies). The implication is that the number of galaxies in our 'observable' sliver of the universe alone is probably in the hundreds of billions. So a crude low-ball estimate of the number of stars in the observable universe would probably then be ~15,000,000,000,000,000,000,000, give or take (and based on observations of our own galaxy so far from the Kepler observatory, if our galaxy is representative, it's probable that a large percentage of these stars have planets, though that is 'scientifically speculative').

So when you look at the night sky, consider that in each roughly Moon-sized area, you're looking at millions of galaxies. We're inconceivably tiny. (I suspect each of these galaxies probably teems with life.)




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