NASA marks verification of 1,000th planet

From NASA Reports
Using data from NASA's Kepler telescope, researchers have verified more planets. Artist concept: NASA.
Using data from NASA's Kepler telescope, researchers have verified more planets. Artist concept: NASA.
Researchers have verified the 1,000th planet spotted by NASA’s Kepler Space Telescope, the space agency reports.

      The Kepler telescope monitored more than 150,000 stars beyond our solar system and has found more than 4,000 candidate planets for further study. Scientists reached the 1,000th milestone after validating that eight more candidates spotted by the planet-hunting telescope are, in fact, planets.
     The Kepler team has added 554 candidates to the roll of potential planets, six of which are near-Earth-size and orbit in the habitable zone of stars similar to our sun. Three newly validated planets are in their distant suns’ habitable zone, the distance from the host star where liquid water might exist on the surface of an orbiting planet. Of the three, two are likely made of rock, like Earth, according to a space agency news release.
     To determine whether a planet is made of rock, water or gas, scientists must know its size and mass. When its mass can’t be directly determined, scientists can infer what the planet is made of based on its size.
     Two of the newly validated planets, Kepler-438b and Kepler-442b, are less than 1.5 times the diameter of Earth. Kepler-438b, 475 light-years away, is 12 percent bigger than Earth and orbits its star once every 35.2 days. Kepler-442b, 1,100 light-years away, is 33 percent bigger than Earth and orbits its star once every 112 days.
     Kepler-438b and Kepler-442b orbit stars smaller and cooler than our sun, making the habitable zone closer to their parent star, in the direction of the constellation Lyra. The research paper reporting this finding has been accepted for publication in The Astrophysical Journal.
     With the detection of 554 more planet candidates from Kepler observations conducted May 2009 to April 2013, the Kepler team has raised the candidate count to 4,175. Eight of these new candidates are between one to two times the size of Earth, and orbit in their sun's habitable zone. Of these eight, six orbit stars that are similar to our sun in size and temperature. All candidates require follow-up observations and analysis to verify they are actual planets.
     Work is underway to translate these recent discoveries into estimates of how often rocky planets appear in the habitable zones of stars like our sun, a key step toward NASA's goal of understanding our place in the universe.
     Kepler’s camera detects planets by looking for transits -- when a distant star dims slightly as a planet crosses before it. The smaller the planet, the weaker the dimming, so brightness measurements must be precise. To achieve that precision, the spacecraft must hold steady.
     In May 2013, data collection during Kepler's extended prime mission came to an end with the failure of the second of four reaction wheels used to stabilize the spacecraft. Even so, scientists and engineers developed a strategy to use pressure from sunlight as a virtual reaction wheel to help control the spacecraft. As a result, the new mission, called K2, will continue Kepler’s planet hunt.  


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