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UC: Life May Be Possible on Billions of Planets in Our Galaxy, Scientists Say

When E.T. tries to call home, he may get a busy signal. There are tens of billions of planets in the Milky Way Galaxy that are potentially able to support life, according new findings by researchers at UC Berkeley and the University of Hawaii.

Ever wonder how many planets outside our solar system could harbor life?

Astronomers at UC Berkeley and the University of Hawaii say it could be many billions – just in our galaxy alone.

New findings using data from the Kepler space telescope and the Keck telescopes in Hawaii indicate that there are "several tens of billions of potentially habitable, Earth-size planets in the Milky Way Galaxy," UC Berkeley announced in a press release today, Monday.

"When you look up at the thousands of stars in the night sky, the nearest sun-like star with an Earth-size planet in its habitable zone is probably only 12 light years away and can be seen with the naked eye. That is amazing," said UC Berkeley graduate student Erik Petigura. Petigura, who was quoted in the news release, led the Kepler data analysis.

The researchers looked for planets around stars similar to the Sun and that are comparable to Earth in surface temperature and size. Eligible planets couldn't be too close or too far from their stars, and the light they receive must be between four times and one-quarter the amount that Earth receives from the Sun. 

Planets like hard-baked Mercury or gas giants like Jupiter didn't make the cut.

UC Berkeley astronomy professor Geoffrey Marcy was quoted saying the results provide an answer to the key question behind the Kepler mission:

"The primary goal of the Kepler mission was to answer the question, ‘When you look up in the night sky, what fraction of the stars that you see have Earth-size planets at lukewarm temperatures so that water would not be frozen into ice or vaporized into steam, but remain a liquid, because liquid water is now understood to be the prerequisite for life? Until now, no one knew exactly how common potentially habitable planets were around sun-like stars in the galaxy."

Marcy, Petigura and Andrew Howard, a former Cal post-doc now on the faculty at the University of Hawaii, will publish their results this week in the online edition of the journal Proceedings of the National Academy of Sciences.

Funding for the research was provided by UC Berkeley and the National Science Foundation, with assistance of the W. M. Keck Observatory and NASA, the campus said.


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