Saturday, June 22, 2013

Are the Sun and Earth Insignificant?

Have you ever heard that the Earth is "just" an insignificant planet orbiting around an "average" star? Well, forget that! I'm reading Rare Earth: Why Complex Life is Uncommon in the Universe, by Ward and Brownlee. These are two guys who study astrobiology, the field that looks at requirements for life to exist elsewhere in our universe.

It turns out that our star is far from average. Here's just a few quick facts:
  1. Our Sun is a yellow star. This very fact means that it is bigger than 95% of all the stars in our Milky Way galaxy. The "average" star is a red dwarf. These ruddy fellows are too small and don't put out enough energy to support any intelligent life.
  2. Our Sun is not a blue star. Blue stars are the hottest stars. They release most of their energy in the UV part of the spectrum. You know, the put-your-sunscreen-on-or-you-will-get-a-nasty-sunburn type of UV - same stuff. Living under a permanent tanning bed is not the ideal way to encourage meaningful life.
  3. Our Sun's brightness is quite stable. Some stars are variable stars, which means they, well, vary their brightness. Not good for life. It would be like trying to bake your cake as your oven fluctuates its temperature wildly and frequently.
A ton more things could be said, but I'll leave it there for now. Our Sun is very, very, very unique.

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