Explanation:
How common are Earth-sized planets?
Quite common,
according to
extrapolations from new data taken by NASA's orbiting
Kepler spacecraft.
Current computer
models
are indicating that at least one in ten stars are orbited by an
Earth-sized planet, making our Milky Way Galaxy the home to over ten
billion Earths.
Unfortunately, this estimate applies only to planets effectively inside
the orbit of Mercury, making these hot-Earths
poor vacation opportunities for humans.
This histogram depicts the
estimated fraction of stars that have close
orbiting planets of various sizes.
The number of Sun-like stars with Earth-like planets in Earth-like
orbits is surely much less, but even so, Kepler has also just announced
the discovery of
four more of those.
