Anand

Introduction

Kepler-22b is the first confirmed extra solar planet found by NASA’s Kepler Space Telescope to orbit within the habitable zone of a Sun-like star. Kepler-22b, a possible super-Earth, is 600 light years away from Earth, in orbit around Kepler-22, a G-type star.

The discovery was announced December 5, 2011. The planet was originally discovered on Kepler’s third day of science operations in mid-2009. The third transit was detected in late 2010. Additional confirmation data was provided by the Spitzer Space Telescope and ground-based observations.

Kepler-22b’s radius is roughly 2.4 times the radius of Earth, or about 60% that of Neptune. Its mass and surface composition remain unknown, with only some very rough estimates established: It has less than 124 Earth masses at the 3 sigma confidence limit, and less than 36 Earth masses at 1 sigma confidence.

It has been estimated that it is probably a “Neptunian” (i.e. mass similar to Neptune) planet with a mass of ~35 Earth masses. There are the possibilities that it could be an “ocean-like” world with only some 10 Earth masses. It might also be comparable to GJ 1214 b in terms of radius, but Kepler-22b is, unlike that planet, in the habitable zone. If it has an Earth-like density (5.515 g/cm³) then it would contain 13.8 Earth masses, while its surface gravity would be 2.4 times Earth’s.

Since Kepler-22b is substantially larger than our planet, it is likely to have a different composition than Earth, and depending on its actual mass, the planet could be rocky, liquid, or gaseous.

If it is mostly ocean with a small rocky core, Natalie Batalha, one of the scientists on the project, speculated “it’s not beyond the realm of possibility that life could exist in such an ocean.” This possibility of life has spurred SETI to perform research on top candidates for extraterrestrial intelligence. However, if the planet’s carbon cycle has ceased due to lack of oceans and plate tectonics, Kepler-22b may turn out to be a searing, sterile super-Venus.

NASA’s Kepler Team

NASA’s Kepler mission has confirmed its first planet in the “habitable zone,” the region where liquid water could exist on a planet’s surface. Kepler also has discovered more than 1,000 new planet candidates, nearly doubling its previously known count. Ten of these candidates are near-Earth-size and orbit in the habitable zone of their host star. Candidates require follow-up observations to verify they are actual planets.

The newly confirmed planet, Kepler-22b, is the smallest yet found to orbit in the middle of the habitable zone of a star similar to our sun. The planet is about 2.4 times the radius of Earth. Scientists don’t yet know if Kepler-22b has a predominantly rocky, gaseous or liquid composition, but its discovery is a step closer to finding Earth-like planets.

Previous research hinted at the existence of near-Earth-size planets in habitable zones, but clear confirmation proved elusive. Two other small planets orbiting stars smaller and cooler than our sun recently were confirmed on the very edges of the habitable zone, with orbits more closely resembling those of Venus and Mars.

“This is a major milestone on the road to finding Earth’s twin,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. “Kepler’s results continue to demonstrate the importance of NASA’s science missions, which aim to answer some of the biggest questions about our place in the universe.”

Kepler discovers planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets that cross in front, or “transit,” the stars. Kepler requires at least three transits to verify a signal as a planet.

“Fortune smiled upon us with the detection of this planet,” said William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field, Calif., who led the team that discovered Kepler-22b. “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.”

The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

Kepler-22b is located 600 light-years away. While the planet is larger than Earth, its orbit of 290 days around a sun-like star resembles that of our world. The planet’s host star belongs to the same class as our sun, called G-type, although it is slightly smaller and cooler.

Of the 54 habitable zone planet candidates reported in February 2011, Kepler-22b is the first to be confirmed. This milestone will be published in The Astrophysical Journal.

The Kepler team has hosting its inaugural science conference at Ames Dec. 5-9 2011, announcing 1,094 new planet candidate discoveries. Since the last catalog was released in February, the number of planet candidates identified by Kepler has increased by 89 percent and now totals 2,326. Of these, 207 are approximately Earth-size, 680 are super Earth-size, 1,181 are Neptune-size, 203 are Jupiter-size and 55 are larger than Jupiter.

The findings, based on observations conducted May 2009 to September 2010, show a dramatic increase in the numbers of smaller-size planet candidates.

Kepler observed many large planets in small orbits early in its mission, which were reflected in the February data release. Having had more time to observe three transits of planets with longer orbital periods, the new data suggest that planets one to four times the size of Earth may be abundant in the galaxy.

The number of Earth-size and super Earth-size candidates has increased by more than 200 and 140 percent since February, respectively.

There are 48 planet candidates in their star’s habitable zone. While this is a decrease from the 54 reported in February, the Kepler team has applied a stricter definition of what constitutes a habitable zone in the new catalog, to account for the warming effect of atmospheres, which would move the zone away from the star, out to longer orbital periods.

“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,” said Natalie Batalha, Kepler deputy science team lead at San Jose State University in San Jose, Calif. “The more data we collect, the keener our eye for finding the smallest planets out at longer orbital periods.”

NASA’s Ames Research Center manages Kepler’s ground system development, mission operations and science data analysis. NASA’s Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development.

Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data. Kepler is NASA’s 10th Discovery Mission and is funded by NASA’s Science Mission Directorate at the agency’s headquarters.

NASA’s Declaration

In another step toward finding Earth-like planets that may hold life, NASA said on 5^th December 2011 the Kepler space telescope has confirmed its first-ever planet in a habitable zone outside our solar system.

French astronomers earlier this year confirmed the first rocky exoplanet to meet key requirements for sustaining life. But Kepler-22b, initially glimpsed in 2009, is the first the US space agency has been able to confirm.

Confirmation means that astronomers have seen it crossing in front of its star three times. But it doesn’t mean that astronomers know whether life actually exists there, simply that the conditions are right.

Such planets have the right distance from their star to support water, plus a suitable temperature and atmosphere to support life.

“We have now got good planet confirmation with Kepler-22b,” said Bill Borucki, Kepler principal investigator at NASA Ames Research Center.

“We are certain that it is in the habitable zone and if it has a surface, it ought to have a nice temperature,” he told reporters.

Spinning around its star some 600 light years away, Kepler-22b is 2.4 times the size of the Earth, putting it in class known as “super-Earths,” and orbits its Sun-like star every 290 days.

Its near-surface temperature is presumed to be about 72 degrees Fahrenheit (22 Celsius). Scientists do not know, however, whether the planet is rocky, gaseous or liquid.

The planet’s first “transit,” or star crossover, was captured shortly after NASA launched its Kepler spacecraft in March 2009.

NASA also announced that Kepler has uncovered 1,094 more potential planets, twice the number it previously had been tracking, according to research being presented at a conference in California on December 2011.

Kepler is NASA’s first mission in search of Earth-like planets orbiting suns similar to ours, and cost the US space agency about $600 million.

It is equipped with the largest camera ever sent into space — a 95-megapixel array of charge-coupled devices — and is expected to continue sending information back to Earth until at least November 2012.

Kepler is searching for planets as small as Earth, including those orbiting stars in a warm, habitable zone where liquid water could exist on the surface of the planet.

The latest confirmed exoplanet that could support life brings to three the total number confirmed by global astronomers.

In addition to French astronomers’ confirmed finding of Gliese 581d in May, Swiss astronomers reported in August that another planet, HD 85512 b, about 36 light years away seemed to be in the habitable zone of its star.

However, those two planets are “orbiting stars smaller and cooler than our Sun,” NASA said in a statement, noting that Kepler-22b “is the smallest yet found to orbit in the middle of the habitable zone of a star similar to our Sun.”

“The Europeans have also been very active, actively working on confirming our candidates,” said Natalie Batalha, Kepler deputy science team lead at San Jose State University.

“They have already confirmed two that are published and they have got another batch that are on the preprint servers so those will be, I’m sure, in the published literature soon,” she added.

“So we are just thrilled about this. We need all telescopes observing these candidates so we can confirm as many as possible.”

A total of 48 exoplanets and exomoons are potential habitable candidates, among a total of 2,326 possibilities that Kepler has identified so far.

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