Artist's conception of Kepler 22-b. Credit: NASA/Ames/JPL-Caltech

Kepler Confirms First Planet in Habitable Zone of Sun-Like Star

Article Updated: 24 Dec , 2015

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Scientists from the Kepler mission announced this morning the first confirmed exoplanet orbiting in the habitable zone of a Sun-like star, the region where liquid water could exist on the surface of a rocky planet like Earth. Evidence for others has already been found by Kepler, but this is the first confirmation. The planet, Kepler-22b, is also only about 2.4 times the radius of Earth — the smallest planet found in a habitable zone so far — and orbits its star, Kepler-22, in 290 days. It is about 600 light-years away from Earth, and Kepler-22 is only slightly smaller and cooler than our own Sun. Not only is the planet in the habitable zone, but astronomers have determined its surface temperature averages a comfortable 22 degrees C (72 degrees F). Since the planet’s mass is not yet known, astronomers haven’t determined if it is a rocky or gaseous planet. But this discovery is a major step toward finding Earth-like worlds around other stars. A very exciting discovery, but there’s more…

It was also announced that Kepler has found 1,094 more planetary candidates, increasing the number now to 2,326! That’s an increase of 89% since the last update this past February. Of these, 207 are near Earth size, 680 are super-Earth size, 1,181 are Neptune size, 203 are Jupiter size and 55 are larger than Jupiter. These findings continue the observational trend seen before, where smaller planets are apparently more numerous than larger gas giant planets. The number of Earth size candidates has increased by more than 200 percent and the number of super-Earth size candidates has increased by 140 percent.

According to Natalie Batalha, Kepler deputy science team lead at San Jose State University in San Jose, California, “The tremendous growth in the number of Earth-size candidates tells us that we’re honing in on the planets Kepler was designed to detect: those that are not only Earth-size, but also are potentially habitable. The more data we collect, the keener our eye for finding the smallest planets out at longer orbital periods.”

Regarding Kepler-22b, William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field, California stated: “Fortune smiled upon us with the detection of this planet. The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season.”

Comparison of the Kepler-22 system with our own inner solar system. Credit: NASA/Ames/JPL-Caltech

Previously there were 54 planetary candidates in habitable zones, but this was changed to 48, after the Kepler team redefined the definition of what constitutes a habitable zone in order to account for the warming effects of atmospheres which could shift the zone farther out from a star.

The announcements were made at the inaugural Kepler science conference which runs from December 5-9 at Ames Research Center.

See also the press release from the Carnegie Institution for Science here.

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Michael Currie
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Michael Currie
December 5, 2011 7:48 PM

Fantastic!

Damos Kalaitzidis
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December 5, 2011 7:49 PM

Great news!

Andrew Pierce
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Andrew Pierce
December 6, 2011 4:10 PM

Is it wrong I read that in Professor Farnsworth voice?

burkedc
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burkedc
December 5, 2011 7:50 PM

Wow, great work by the Kepler team!

Kawarthajon
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Kawarthajon
December 5, 2011 8:10 PM

Awesome! When can I visit the new planet?

HeadAroundU
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HeadAroundU
December 6, 2011 12:22 AM

We haven’t destroyed this one yet. grin

Anyway, fantabulous news. I think I should go back to planethunting…

Jim Conditt
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Jim Conditt
December 5, 2011 9:13 PM

So…if we can create a ship that travels at the speed of light, and we drive it for a little over 600 years, we can start mining, clear cutting, and over populating Kepler 22b. Sweet!

Chad Fenwick
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Chad Fenwick
December 5, 2011 9:40 PM

Awesome! Saving up for my tickets.

hunterz85
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December 5, 2011 9:46 PM

The planet, Kepler-22b, is also only about 2.4 times the radius of Earth

Sweet…!!! More space less Rent…

Donald Kines
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Donald Kines
December 5, 2011 10:16 PM

I’m guessing that when the Kepler mission is complete the estimate for the number of planets in our galaxy will be at least 500 billion and the number of earth-like planets in the habitable zone will be at least 10 billion, far more than most people’s expectation. Yet again, the Copernican principle holds up; we are not unique.

henk
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henk
December 5, 2011 10:41 PM

how old is that star ?

Peter
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Peter
December 5, 2011 11:06 PM

How far is Kepler looking? How many stars are within 100 light years of Sol? Is there a plan now to train telescopes and spectrometers on this planet to see if we can detect an atmosphere or any radio signals? 600 light years is a little far to get excited about. I’m thinking anything within a radius of 30-50 light years would be more likely to promote a probe shot. At least our kids would know if it’s really as nice as it sounds!

Torbjorn Larsson OM
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Torbjorn Larsson OM
December 6, 2011 8:46 PM
Kepler has a good telescope, it is the detection method of transits obscuring the stars that is limiting. IIRC it will be best between 1000 – 3000 ly away. The point of the mission is not to locate nearby habitables but to survey a good sample, so missions that look at nearby stars can be designed. Those missions will look for more of planetary characteristics, including signs of life. (Say, oxygen atmosphere on a habitable zone terrestrial.) I don’t think anyone is pondering probes, which are unrealistic, they will always be too expensive. But we can answer a long standing question of culture: “are we alone?” And we can do better science: study how planetary systems and planets… Read more »
Harry
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Harry
December 5, 2011 11:39 PM

Man Nasa is doing good im glad to see they have made this discovery but it would be cool to send a machine that can record a video to Kepler-22b.But that would take a extremely long time.We should try making life on mars or one of Jupiter moons.

Symbol
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Symbol
December 6, 2011 12:51 AM

If there is an advanced civilization there we would totally kick there butts in a war.

Franco J. Torres
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December 6, 2011 2:36 AM

What would the gravity feel like on a planet that size?

James Jenkins
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James Jenkins
December 6, 2011 5:26 AM

It depends on the density of the planet as well the size. Densities can vary significantly.

magnus.nyborg
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magnus.nyborg
December 6, 2011 8:05 AM

If the planet is saturn-like (gaseous) the gravity might be similar to earth, maybe alittle higher. That seems unlikely though.

If it is a rocky planet, it would probably weigh in at something like 40-80Mearth, with a gravity around 6-12x earths. Highly unlikely.

Neptune type seems more plausible, with a large rocky core and a very thick and dense atmosphere. Gravity somewhere near 2-3x earth.

(gravity as in what we call surface gravity, g=9.82m/s^2)

William928
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William928
December 7, 2011 12:49 AM

How did you arrive at these figures, mere speculation? Why don’t we wait for more data to come in before condemning the possibility that Kepler 22b MAY be earthlike…….

squidgeny
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squidgeny
December 7, 2011 1:41 PM

The figures can be calculated from GM/(r^2).

We don’t know the mass M, but we know the size, so given a density D, the surface gravity is given by DG(4/3)(pi)r

All those are known values, except D. So we can plug in different Ds (earth-density, saturn-density, neptune-density etc) and arrive at a surface gravity for each speculation.

It’s worth pointing out that if the planet doesn’t have a solid surface, the prospect for complex life is grim…

William928
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William928
December 7, 2011 11:46 PM

Thanks, but I wasn’t asking about potential surface gravity. LC answered my question above.

magnus.nyborg
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magnus.nyborg
December 8, 2011 10:18 AM

Im not condemning the possibility for being a rocky planet, or actually any possibility

But if it is a rocky planet, with a radius of 2.4Rearth, then the core will be heavily crushed almost bordering to degenerate, and the surface gravity will be very large. It would also be very unlikely that its just rock and metals, and almost no gases or volatiles, making the case for something inbetween. And the inbetween cases dont look like exactly an earthlike planet.

Although i didnt provide the guesswork and calculations, it still is possible to limit off the possibilities. None of that limits off the possibilities for life though

bdlaacmm
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bdlaacmm
December 6, 2011 12:59 PM

Don’t anyone get your hopes up over this being an “Earthlike” planet. The relatively large diameter almost certainly means that if it does have an atmosphere, its surface density would be crushingly great. Also note that it lies on the extreme inner edge of the Habitable Zone. If anything, this might be a “Venuslike” world; certainly no place we’d care to visit!

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
December 6, 2011 8:35 PM

Not so crushing as life goes. Deep sea multicellulars manage ~ 1000’s of atmospheres pressure. As a comparison, Venus has ~ 100 atmospheres pressure at the surface.

You will have to look again at the HZ figures: Borucki made a huge point that this planet is as much or little marginal as Earth relatively seen, while earlier potential habitables have been marginal.

Dark Gnat
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Dark Gnat
December 6, 2011 1:37 PM

Probably a very hot, smoggy, high pressure world. Worse than L.A.

I wonder if this could be a water planet, though.

Robert O'Coillean
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Robert O'Coillean
December 6, 2011 2:32 PM

so, this planet is 2.4 times the size of Earth … what would that mean in population capacity? More than 2.4 times Earth’s capacity, I’m sure, but I get lost in calculations beyond that. Anybody got an educated guess?

Anonymous
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Anonymous
December 6, 2011 4:10 PM

It really is anyone’s guess at this point. However if I was a betting man I’d say it’s likely 0.

This planet is large enough to be either a super Earth or Neptunian, and likely to have a more dense atmosphere then Earth. Given it’s proximity to the star it could very well could share similar characteristics as Venus, especially if it has a dense atmosphere. A gas giant would be uninhabitable.

squidgeny
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squidgeny
December 7, 2011 1:47 PM

The surface area of a sphere is given by 4(pi)(r^2). If the radius is 2.4 times greater, the surface area is nearly 6 times greater.

Of course, the human population capacity of a planet depends on a hell of a lot more than space… as it stands there’s a good chance it’s uninhabitable by humans. Even if inhabited by alien life, it might very well still be uninhabitable to us.

Abu bakar Siddique
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December 6, 2011 2:42 PM

Somebody will go there in future.

Anonymous
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Anonymous
December 6, 2011 4:21 PM
Unlikely. The fastest human vehicle sent to date is Voyager 1, which is traveling at 17.46 km/s. It would take Voyager 1 about 74,000 years to travel the 4.3 light years to Alpha Centauri (nearest start system). That’s probably about the best we’d be able to do with chemical rockets. We may be able to develop faster propulsion technologies this century, including Nuclear Pulse Propulsion, the Fresnel Lens Sail or fusion. However, none of these offer a viable technology that could get us 600 light years out. A Earth-Analog >10 light years is reachable within most of our lifetimes, with some major technological upgrades. 20-50 light years may also be reachable in the very long term. As long… Read more »
aerandir
Member
December 6, 2011 10:21 PM

He said future, not near future. Who knows what the human civilization will be like 10,000, or 100,000 or even a million years from now. We may be non-existent, or we may be ubiquitous in our galaxy. I’m almost positive that at some point way ahead in time, Earth may not even be a ‘headquarters’ to return telemetry to. Earth will just be one of many sites of human (or human-like) colonization. Its heritage as our birthplace, our cradle, will be long forgotten by those descendants who dwell amongst the various celestial objects out there.

wjwbudro
Member
wjwbudro
December 6, 2011 11:19 PM

Very poetic and sci-fi however, the hurdle is EM and relativity. Unless those hurdles can be cleared, traveling and communicating in a space network environment even in our galactic back yard will be next to impossible. It would be comparable to going from the era Lewis and Clark or even the pony express to today’s technology. Sorry had to throw that in.

aerandir
Member
December 6, 2011 11:50 PM

Well if its comparable to that, then clearly by your analogy it’s possible, as manifested by this technological development that actually happened. No one 500 years ago would have believed that we can now talk to anyone on the planet instantaneously (practically speaking) or that people walked on the moon or a number of amazing things. When it comes to the distant future, it’s nice to dream a little.

wjwbudro
Member
wjwbudro
December 7, 2011 12:48 AM

Your right. I shouldn’t have analogized but, the hurdle(s) still remain.

squidgeny
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squidgeny
December 7, 2011 1:52 PM

I really do dislike the appeal to technological miracles. Sure, we might develop faster-than-light travel, but by the same token we might develop a way to focus quantum fluctuations and have whole new habitable planets blink into existence right in our own solar system, doing away with the need for FTL anyway.

Who’s to say which is likelier?

Anonymous
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Anonymous
December 6, 2011 4:21 PM
Unlikely. The fastest human vehicle sent to date is Voyager 1, which is traveling at 17.46 km/s. It would take Voyager 1 about 74,000 years to travel the 4.3 light years to Alpha Centauri (nearest start system). That’s probably about the best we’d be able to do with chemical rockets. We may be able to develop faster propulsion technologies this century, including Nuclear Pulse Propulsion, the Fresnel Lens Sail or fusion. However, none of these offer a viable technology that could get us 600 light years out. A Earth-Analog >10 light years is reachable within most of our lifetimes, with some major technological upgrades. 20-50 light years may also be reachable in the very long term. As long… Read more »
Anonymous
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Anonymous
December 6, 2011 4:25 PM

So… Jim Conditt, let Kepler 22b, and any other other planet to foound, free from stupid humans, especiallly if there are Americans… You’re destroying the Earth, it’s more that enough…

Anonymous
Guest
Anonymous
December 6, 2011 4:25 PM

So… Jim Conditt, let Kepler 22b, and any other other planet to foound, free from stupid humans, especiallly if there are Americans… You’re destroying the Earth, it’s more that enough…

Anonymous
Guest
Anonymous
December 6, 2011 4:25 PM

So… Jim Conditt, let Kepler 22b, and any other other planet to foound, free from stupid humans, especiallly if there are Americans… You’re destroying the Earth, it’s more that enough…

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