Scientists are searching for Earth-like planets with the Kepler space telescope. It works by detecting periodic variations in the brightness of stars caused by orbiting exoplanets passing in front of them.
In February 2011 the Kepler team announced they had found 54 planets thought to be suitable for life because they lie in their stars' habitable zones. Five of these planets are Earth-sized.
Image: An illustration of Kepler (credit: NASA/Kepler mission/Wendy Stenzel)
A mission hunts for exoplanets similar to the Earth.
NASA's William Borucki explains Kepler's mission.
Launched in 2009, the Kepler space telescope's mission is to find Earth-like worlds orbiting distant stars. In this clip, NASA's William Borucki explains how it will work.
Kepler is a space observatory launched by NASA to discover Earth-like planets orbiting other stars. The spacecraft, named after the Renaissance astronomer Johannes Kepler, was launched on March 7, 2009.
Designed to survey a portion of our region of the Milky Way to discover dozens of Earth-size extrasolar planets in or near the habitable zone and estimate how many of the billions of stars in our galaxy have such planets,Kepler's sole instrument is a photometer that continually monitors the brightness of over 145,000 main sequence stars in a fixed field of view. These data are transmitted to Earth, then analyzed to detect periodic dimming caused by extrasolar planets that cross in front of their host star.
Kepler is part of NASA's Discovery Program of relatively low-cost, focused primary science missions. The telescope's construction and initial operation were managed by NASA's Jet Propulsion Laboratory, with Ball Aerospace responsible for developing the Kepler flight system. The Ames Research Center is responsible for the ground system development, mission operations since December 2009, and science data analysis. The initial planned lifetime was 3.5 years, but greater than expected noise in the data, from both the stars and the spacecraft, meant additional time was needed to fulfill all mission goals. Initially, in 2012, the mission was expected to last until 2016, but this would only be possible if all remaining reaction wheels used for pointing the spacecraft remained reliable. On May 11, 2013, a second of four reaction wheels failed, disabling the collection of science data and threatening the continuation of the mission.
As of July 2013[update], Kepler had found 134 confirmed exoplanets in 76 stellar systems, along with a further 3,277 unconfirmed planet candidates. In November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy. 11 billion of these estimated planets may be orbiting sun-like stars. The nearest such planet may be 12 light-years away, according to the scientists.
On August 15, 2013, NASA announced that they have given up trying to fix the two failed reaction wheels. This means the current mission needs to be modified, but it does not necessarily mean the end of planet-hunting. NASA has asked the community to propose alternative mission plans "potentially including an exoplanet search, using the remaining two good reaction wheels and thrusters". On November 18, 2013, the K2 (also named "Second Light") plan proposal, which may include utilizing the disabled Kepler in a way that could detect habitable planets around smaller, dimmer red dwarf stars, was reported and, later, presented in more detail.
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