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Milky Way Awash in Planets

Since the last Kepler catalog was released in February 2012, the number of candidates discovered in the Kepler data has increased by 20 percent and now totals 2,740 potential planets orbiting 2,036 stars. Image by NASA.

In case you missed it, a recap on last week’s major exoplanet news. At the American Astronomical Society meeting, scientists presented the first reliable tally of the number of Earth-sized exoplanets in our Milky Way. And the number is a staggering 17 billion. That’s one in six stars hosting an Earth-sized planet in a tight orbit, NASA reports.

How many of them could host water — a key to life — is unknown. An Earth-sized planet doesn’t necessarily mean life. Far from from it. But the possibility is there. And it’s an exciting one. It’s up to astronomers now to narrow down which ones are in the habitable zone — that sweet spot where they’re not too far or close to their host stars that they’d either freeze or be too hot to be habitable. (Astronomers also call it the Goldilocks zone.)

Researchers for NASA’s planet-hunting space telescope, Kepler also announced that they had discovered 461 new planet candidates — four of which are less than twice the size of Earth and located in the habitable zone. This brings the number of Kepler discoveries to 2,740 potential planets orbiting 2,036 stars. Of those, 105 have been confirmed.

Rebecca J. Rosen describes it well in this Atlantic story:

“So, in just two decades (i.e. since yesterday in astronomical terms), we’ve gone from no certainty that there was even one planet beyond our solar system, to knowing that there are at least 105 and having pretty good reason to believe there are billions and billions more, a galaxy just crawling with them, like ants on a picnic’s discarded strawberry.”

As seen in the NASA graph above, discoveries of Earth-size and super Earth-size planet candidates account for the most dramatic increases. They grew by 43 and 21 percent respectively, according to NASA.

In an earlier interview with the NewsHour, Geoff Marcy, a University of California, Berkeley astronomer and a co-investigator on the Kepler team, explained an Earthlike planet to the NewsHour this way: “The darn thing better be solid so that life can form in the ooze and puddles and gook on the surface of the planet,” Marcy said. “So you need a surface. Second…it must have conditions that make it suitable for life. It can’t be scorching hot and it can’t be frigid cold.”


  • In this Nature paper published on Jan. 13, scientists provide detailed computer reconstructions of the prehistoric tetrapods and find that their skeletal structure is totally different than our traditional understanding.

  • Might it be possible to improve your memory while you sleep? Miles O’Brien poses the question for the National Science Foundation’s* latest Science Nation piece.

  • Astronomers have discovered the largest known structure in the universe, Space.com reports, “a clump of active galactic cores that stretches 4 billion light-years from end to end.”

  • A window into the writing process of the brilliant John McPhee, by John McPhee. Including an unusual piece of office furniture that aided his writing — a sheet of plywood resting on two sawhorses, covered with three-by-five organizing note cards. His essay is in the Jan. 14 issue of the New Yorker.

  • This giant squid was filmed in the wild by a Japanese camera crew.

  • An international team of climate researchers has written and published an open letter in the journal Nature Climate Change, describing wind and wave pattern changes expected to come about due to global warming.


*For the record, the National Science Foundation is an underwriter of the NewsHour.

Tom Kennedy and Patti Parson contributed to this report.

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