The fourth potentially habitable planet in our galaxy has just been discovered, 22 light years from Earth. This planet, called GJ 667Cc, is too large to be called Earth's twin. It might more properly be called Earth's Big Brother. GJ 667Cc is 4.5 times the mass of Earth, and it orbits its star in 28.15 days, roughly the equivalent of one Earth month.
An international group of scientists, who published their announcement in Astrophysical Journal Letters, say GJ 667Cc is the best candidate so far "to support liquid water and, perhaps, life as we know it."
In a recent Big Think interview, theoretical physicist Dr. Michio Kaku described the search for Earth's twin as the "Holy Grail of planetary astronomy." In the case of other potentially habitable planets, the next step after discovery, according to Kaku, is for scientists to "discern if we can find out what their atmospheres are like. Do they have oxygen? Do they have H2O?" Then send in SETI with their eavesdropping devices to "see if there are any radio emissions from intelligent beings on these planets."
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