Great Filter Material

Eliezer S. Yudkowsky (
Thu, 24 Jun 1999 04:31:29 -0500

What makes the Sun special? [Edited a bit...]

> The Sun is a single star whereas most stars are in
> multiple systems. It is among the most massive 10 per
> cent of stars in its neighbourhood. It also has 50 per
> cent more heavy elements than other stars of its age
> and type, and about a third of the variation in
> brightness.
> Its orbit is significantly less elliptical than that of
> other stars of its age and type, and hardly inclined at
> all to the Galactic plane. What's more, the Sun is
> orbiting very close to the "corotation radius" for the
> Galaxy-the place at which the angular speed of the
> spiral pattern matches that of the stars.
> Stable planetary orbits such as the Earth's are much more
> likely around single stars like the Sun. For a massive
> star with inhabitable planets that are relatively far
> away, stellar flare-ups would be little threat to the
> planets. Heavy elements are essential to make
> planets like Earth, and a star with a stable light
> output is essential for life.
> As for the orbit of the Sun, its circularity prevents
> it plunging into the inner Galaxy where
> life-threatening supernovae are more common. And
> its small inclination to the Galactic plane prevents
> abrupt crossings of the plane that would stir up the
> Sun's Oort Cloud and bombard the Earth with comets.

> By being near the Galaxy's corotation radius, the Sun
> avoids crossing the spiral arms too often, an event
> that would expose it to supernovae, which are more
> common there.
> Because life-bearing stars have to be close to the
> corotation radius, that rules out more than 95 per
> cent of stars in the Galaxy in one fell swoop.

           Eliezer S. Yudkowsky
Running on BeOS           Typing in Dvorak          Programming with Patterns
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