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The Holy Grail of Planetary Astronomy
As noted in a prior post, not only are planets numerous, there are more planets than stars in the Milky Way and presumably in other galaxies. NASA’s Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. Previously Gliese 581g was discovered as a potential earth-like planet in the habitable zone.
Michio Kaku on The Holy Grail of Planetary Astronomy: The Search for Earth's Twin Dr. Kaku addresses the following question: A recently discovered planet named Kepler 22b apparently has a very, very similar composition to Earth, although I don't think they have it exactly figured out yet. What do discoveries like this mean and what is the possibility of many other earth-like planets being out there?
Gliese 581 System
Planets More Common in Milky Way than Stars: Planets Everywhere
Kepler Discovers First Earth-Sized Planets Outside Solar System
Exoplanet Gliese 581g Might Support Life