Kepler's mission is to detect minute changes in the light curve of a star as a possible indication of a transiting planet. Below is an example of a recorded light curve from the earliest detected transits.
Examples of Kepler light curves from early detected planetary transits. View larger image.
(Courtesy of NASA)
To be a candidate, at least three transits must be detected. This also gives a precise measure of the orbital period of the planet. From the star's absolute luminosity, its mass can be inferred, and from the modulation depth of the light curve, the orbital distance and size of the planet can be estimated. The planet's mass can be estimated from independent ground-based spectroscopic measurements of the radial motion of the host star.
Each year, as more data is analyzed, more planets, of smaller size and longer orbital periods, are detected. After three years of analyzed data, 3,538 planet candidates have been identified. These range from huge gas giants bigger than Jupiter to tiny planets much smaller than Earth. This image shows the current distribution of planet sizes and orbital periods including the latest data released on November 4, 2014.
"There is a wide variety of systems out there," Jason Rowe, research scientist, SETI Institute, Mountain View, Calif., said during the press conference. "If you can imagine it, there is probably a system like that out there. We are finding more and more earth like planets."
The loss of Kepler
Sadly, as of May, 2013, the Kepler spacecraft is unable to continue its primary mission. The second reaction wheel failed. A minimum of three are required to enable the precision pointing accuracy needed for these high-precision photometric measurements. Even so, the data collection period lasted more than a year longer than the planned three and a half year mission.
The results reported on November 4 include analysis of only the first three years of observations. Though Kepler is resting in safe mode in its orbit around the sun, Earth-based scientists will continue to analyze the last year and a half of recorded data extending the list of transiting planet candidates.
If you want to participate in the hunt for new planets, join the citizen science project underway at www.PlanetHunters.org.
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