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Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone of a Sun-like Star

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Read also: Kepler 22-b: Earth-like planet confirmed

William J. Borucki et al

Folded light curve with model fit in red. Black dots represent individual observations. Dark blue points represent 30-minute binned data, and cyan points represent residuals after fitting. Red asterisk represents the mid-transit times based on the model fit with eccentricity value allowed to float

A search of the time-series photometry from NASA’s Kepler spacecraft reveals a transiting planet candidate orbiting the 11th magnitude G5 dwarf KIC 10593626 with a period of 290 days. The characteristics of the host star are well constrained by high-resolution spectroscopy combined with an asteroseismic analysis of the Kepler photometry, leading to an estimated mass and radius of 0.970 +/- 0.060 MSun and 0.979 +/- 0.020 RSun. The depth of 492 +/- 10ppm for the three observed transits yields a radius of 2.38 +/- 0.13 REarth for the planet.
The system passes a battery of tests for false positives, including reconnaissance spectroscopy, high-resolution imaging, and centroid motion.
A full BLENDER analysis provides further validation of the planet interpretation by showing that contamination of the target by an eclipsing system would rarely mimic the observed shape of the transits.

Image of the star field near Kepler-22

The final validation of the planet is provided by 16 radial velocities obtained with HIRES on Keck 1 over a one year span.
Although the velocities do not lead to a reliable orbit and mass determination, they are able to constrain the mass to a 3{\sigma} upper limit of 124 MEarth, safely in the regime of planetary masses, thus earning the designation Kepler-22b.
The radiative equilibrium temperature is 262K for a planet in Kepler-22b’s orbit.
Although there is no evidence that Kepler-22b is a rocky planet, it is the first confirmed planet with a measured radius to orbit in the Habitable Zone of any star other than the Sun.

Characteristics of Kepler-22 and -22b

Read more: ttp://arxiv.org/pdf

Written by physicsgg

December 8, 2011 at 7:11 am

Posted in ASTRONOMY, ASTROPHYSICS

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Kepler 22-b: Earth-like planet confirmed

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Astronomers have confirmed the existence of an Earth-like planet in the “habitable zone” around a star not unlike our own.

The planet, Kepler 22-b, lies about 600 light-years away and is about 2.4 times the size of Earth, and has a temperature of about 22C.

It is the closest confirmed planet yet to one like ours – an “Earth 2.0”.

However, the team does not yet know if Kepler 22-b is made mostly of rock, gas or liquid.

During the conference at which the result was announced, the Kepler team said that it had spotted some 1,094 new candidate planets.

The Kepler space telescope was designed to look at a fixed swathe of the night sky, staring intently at about 150,000 stars. The telescope is sensitive enough to see when a planet passes in front of its host star, dimming the star’s light by a minuscule amount.

Kepler identifies these slight changes in starlight as candidate planets, which are then confirmed by further observations by Kepler and other telescopes in orbit and on Earth.
Kepler 22-b was one of 54 candidates reported by the Kepler team in February, and is just the first to be formally confirmed using other telescopes.

More of these “Earth 2.0” candidates are likely to be confirmed in the near future, though a redefinition of the habitable zone’s boundaries has brought that number down to 48.

Kepler 22-b lies at a distance from its sun about 15% less than the distance from the Earth to the Sun, and its year takes about 290 days. However, its sun puts out about 25% less light, keeping the planet at its balmy temperature that would support the existence of liquid water.

The Kepler team had to wait for three passes of the planet before upping its status from “candidate” to “confirmed”.

“Fortune smiled upon us with the detection of this planet,” said William Borucki, Kepler principal investigator at Nasa’s Ames Research Center.

“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 results were announced at the Kepler telescope’s first science conference, alongside the staggering number of new candidate planets. The total number of candidates spotted by the telescope is now 2,326 – of which 207 are approximately Earth-sized.

In total, the results suggest that planets ranging from Earth-sized to about four times Earth’s size – so-called “super-Earths” – may be more common than previously thought.

http://www.bbc.co.uk

Written by physicsgg

December 5, 2011 at 7:59 pm

Posted in ASTRONOMY, ASTROPHYSICS

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