NASA Says it discovers first planet in habitable zone.

[Crossroads Inc.]

From Yahoo News

MOUNTAIN VIEW, Calif. — NASA's planet-hunting Kepler spacecraft has confirmed the discovery of its first alien world in its host star's habitable zone — that just-right range of distances that could allow liquid water to exist — and found more than 1,000 new explanet candidates, researchers announced today (Dec. 5).

The new finds bring the Kepler space telescope's total haul to 2,326 potential planets in its first 16 months of operation.These discoveries, if confirmed, would quadruple the current tally of worlds known to exist beyond our solar system, which recently topped 700.

The potentially habitable alien world, a first for Kepler, orbits a star very much like our own sun. The discovery brings scientists one step closer to finding a planet like our own — one which could conceivably harbor life, scientists said.

"We're getting closer and closer to discovering the so-called 'Goldilocks planet,'" Pete Worden, director of NASA's Ames Research Center in Moffett Field, Calif., said during a press conference today. [Gallery: The Strangest Alien Planets]

The newfound planet in the habitable zone is called Kepler-22b. It is located about 600 light-years away, orbiting a sun-like star.
Kepler-22b's radius is 2.4 times that of Earth, and the two planets have roughly similar temperatures. If the greenhouse effect operates there similarly to how it does on Earth, the average surface temperature on Kepler-22b would be 72 degrees Fahrenheit (22 degrees Celsius).
Hunting down alien planets

The $600 million Kepler observatory launched in March 2009 to hunt for Earth-size alien planets in the habitable zone of their parent stars, where liquid water, and perhaps even life, might be able to exist.

Kepler detects alien planets using what's called the "transit method." It searches for tiny, telltale dips in a star's brightness caused when a planet transits — or crosses in front of — the star from Earth's perspective, blocking a fraction of the star's light.

The finds graduate from "candidates" to full-fledged planets after follow-up observations confirm that they're not false alarms. This process, which is usually done with large, ground-based telescopes, can take about a year.

The Kepler team released data from its first 13 months of operation back in February, announcing that the instrument had detected 1,235 planet candidates, including 54 in the habitable zone and 68 that are roughly Earth-size.

Of the total 2,326 candidate planets that Kepler has found to date, 207 are approximately Earth-size. More of them, 680, are a bit larger than our planet, falling into the "super-Earth" category. The total number of candidate planets in the habitable zones of their stars is now 48.
To date, just over two dozen of these potential exoplanets have been confirmed, but Kepler scientists have estimated that at least 80 percent of the instrument's discoveries should end up being the real deal.
More discoveries to come

The newfound 1,094 planet candidates are the fruit of Kepler's labors during its first 16 months of science work, from May 2009 to September 2010. And they won't be the last of the prolific instrument's discoveries.

"This is a major milestone on the road to finding Earth's twin," Douglas Hudgins, Kepler program scientist at NASA headquarters in Washington, D.C., said in a statement.

Mission scientists still need to analyze data from the last two years and on into the future. Kepler will be making observations for a while yet to come; its nominal mission is set to end in November 2012, but the Kepler team is preparing a proposal to extend the instrument's operations for another year or more.
Kepler's finds should only get more exciting as time goes on, researchers say.

"We're pushing down to smaller planets and longer orbital periods," said Natalie Batalha, Kepler deputy science team lead at Ames.
To flag a potential planet, the instrument generally needs to witness three transits. Planets that make three transits in just a few months must be pretty close to their parent stars; as a result, many of the alien worlds Kepler spotted early on have been blisteringly hot places that aren't great candidates for harboring life as we know it.

Given more time, however, a wealth of more distantly orbiting — and perhaps more Earth-like — exoplanets should open up to Kepler. If intelligent aliens were studying our solar system with their own version of Kepler, after all, it would take them three years to detect our home planet.
"We are getting very close," Batalha said. "We are homing in on the truly Earth-size, habitable planets."

Kick ass for Keplar, good on for discovering an Earth like planet so soon in its mission.

[Guardsman Bass]

That planet is pretty big, even for a super-earth. I wonder if it's actually a small gas giant (they didn't give its mass - they might not actually know it yet).

[Sute]

Indeed, they don't know its mass yet, as this article confirms. Makes sense, since Kepler finds planets by measuring how much of the parent star's light they block and mass doesn't figure into that.

Edited for clarity.

[Guardsman Bass]

I wouldn't be surprised if it's one of those "ocean planets" they've speculated on, with an atmosphere plus a water ocean thousands of kilometers deep. Not quite a gas giant (Kepler 22b's radius is still quite a bit smaller than that of Neptune, the smallest gas giant in terms of size if not mass), but not exactly habitable or a twin to Earth.

[Surlethe]

What does "habitable" mean? Does it mean "humans can live there," or does it mean "life could possibly have evolved there"?

[starslayer]

It means that life could possibly have evolved there, though it's usually used as shorthand for "probably has Earth-like conditions" or "could have liquid water on its surface." It doesn't necessarily mean humans would like the place (we have no idea what the atmosphere is actually like).

We won't know the mass until radial velocity data is good enough to measure this planet's effect on the star, or we get really, really, REALLY lucky and see a microlensing event involving this thing.

[Crossroads Inc.]

What does "habitable" mean? Does it mean "humans can live there," or does it mean "life could possibly have evolved there"?

Yeah in this case it is pretty much "Life COULD evolve there"
Finding a true 'earth like' planet may still be decades down the road, as we would need to get more and more refined information for such an identifacation. For right now however this is big news

[Eternal_Freedom]

"Habitable" means "in the habitable zone" - the zone around a particular star where a planet can have liquid water on the surface. Fromt aht you get the "life might evolve there" but liquid water is the key - without it chances of life (As We Know It (TM)) are zip.

Around our sun the habitable zone stretches from a bit further out than Venus to a bit further in than Mars.

[Kryten]

Around our sun the habitable zone stretches from a bit further out than Venus to a bit further in than Mars.

It actually includes Mars-which shows how little just being 'in the habitable zone' means for actual habitability.

[Eternal_Freedom]

Well, Mars can reach 20 degrees C on the surface - so liquid water is possible, but with it's very thin atmosphere the water would boil off quickly.

[LaCroix]

As far as I remember, Mars had a hit from a huge asteroid that pretty much removed all the atmosphere rather early in its history. It probably even melted the northern hemisphere, crating a very different landscape from the southern.

Not wanting to be left behind, the southern hemisphere also has some nice craters to show, one of them 2000km wide.

So life never really had a chance there. Mars simply caught some bullets for us.

[starslayer]

Um, what? Mars lost its atmosphere because its core cooled early in its history, leaving it with no magnetic field. The solar wind then slowly stripped off the atmosphere over the course of several million years. The impact that may have created the Borealis Basin (this has not been proven yet, though there is good evidence for it) almost certainly did not strip off the atmosphere, and even if it did, that impact happened extremely early on in Mars' history; there was ample time for the atmosphere to reform.