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17 billion Earth-size planets estimated to be in our galaxy

By Alicia Chang

Associated Press


LOS ANGELES >> Our Milky Way is home to at least 17 billion planets that are similar in size to Earth, a new estimate suggests. That’s more than two Earth-size planets for every person on the globe.

Just how many are located in the sweet spot where water could exist is “simply too early to call,” said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics, who presented his work at an astronomy meeting Monday.

It’s the first reliable tally of the number of worlds outside the solar system that are the size of Earth, but the hunt for our twin is far from over.

Despite the explosion of exoplanet discoveries in recent years, one find remains elusive: a planet that’s not only the right size, but also in the so-called Goldilocks zone where it’s not too hot or too cold for water to be in liquid form on the surface.

The sheer number of Earth-size planets gives astronomers a starting point to narrow down which ones are in the habitable zone.

Fressin and his team came up with their figure by conducting a fresh analysis of data collected by NASA’s Kepler spacecraft, which was launched in 2009 to track down other Earths. They estimated at least 1 in 6 stars in the galaxy hosts a planet the size of ours, translating to at least 17 billion Earth-size worlds.

Using a different method, a team from the University of California, Berkeley, and University of Hawaii separately came up with a similar estimate. They calculated 17 percent of distant stars have planets that are the same size as Earth or slightly larger.

The findings were presented at the American Astronomical Society in Long Beach, Calif.

Meanwhile, the Kepler spacecraft continues to spot planets as they pass between Earth and the star they orbit. It found 461 new candidate planets, bringing the total to 2,740 potential planets, said mission scientist Christopher Burke at the SETI Institute.

Four of the Kepler finds are thought to reside in the Goldilocks zone, but more observations are needed.

Fressin said it’s clear that rocky planets abound outside the solar system.

“If you look up on a starry night, each star you’re looking at — almost each one of them — has a planetary system,” he said.

Kepler mission:
>> www.nasa.gov/kepler

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Nevadan wrote:
On the last sentence, what is new?
on January 8,2013 | 03:54AM
Nevadan wrote:
Sorry, I can't fault readers from making jokes out of your oral presentation at Long Beach. As William S would say - Much Ado About Nothing.
on January 8,2013 | 04:36AM
palani wrote:
Such speculation is an interesting exercise but, keep in mind, the universe beyond our "little" Milky Way galaxy is infinite. Logic therefore dictates that the number of inhabitable planets is also infinite, and that the odds of an infinite number of these hosting intelligent life is 100%.
on January 8,2013 | 04:02AM
F8TH wrote:
I agree that the universe is infinite as the "nothingness" was there before the universe was created however, I disagree that the the number of galaxies, stars, and planets are infinite. Created matter is finite, even if it is still being created, we just cannot count it and for most of us cannot even conceive the enormity of number.
on January 8,2013 | 05:46AM
Nevadan wrote:
Sorry, I can't fault readers from making jokes out of your Long Beach oral presentation. As William S would say "Much Ado about Nothing".
on January 8,2013 | 04:34AM
sailfish1 wrote:
Are we looking for a place to go after we destroy the planet we are on?
on January 8,2013 | 06:06AM
HonoluluHawaii wrote:
Yes. And i am not FHB.
on January 8,2013 | 06:12PM
Maneki_Neko wrote:
Number 11,976,433 is mine. Keep off.
on January 8,2013 | 07:42AM
st1d wrote:
i got 5318008, the best the milky way has to offer.
on January 8,2013 | 04:53PM
HonoluluHawaii wrote:
Nobody is taking number one away from Obama lol, and we all know it is Earth.
on January 8,2013 | 06:12PM
Skyler wrote:
"Gentlemen, we are not alone..."
on January 8,2013 | 09:37AM
loquaciousone wrote:
What about the ladies? Without them, we would truly be alone.
on January 8,2013 | 01:10PM
HonoluluHawaii wrote:
Lmfao. In fact we would only be Amoeba.
on January 8,2013 | 06:10PM
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