The Kepler Space Telescope's primary mission has ended, NASA announced on Wednesday, but that doesn't mean that it's being shut off.
Launched in 2009, the $591 million telescope was designed to keep constant surveillance on a small patch of sky containing 150,000 stars to measure changes in light from those stars. Regular, minute dips in the stars' brightnesss would be evidence of orbiting planets blocking the stars' light.
The plan was to keep the telescope going for at least three years or so before funding for the program would run out. However, NASA decided back in April to keep the program going through fiscal year 2016.
Since it's been in operation, researchers using the telescope have identified more than 2,300 possible planets orbiting stars other than our own, 100 of which have been confirmed, according to NASA. Of the planet candidates, hundreds are the size of Earth, orbit distances from their host stars where water can exist as a liquid, or both. Liquid water is essential for life as we know it.
Based on Kepler's findings, researchers estimate that at least one-third of stars in our galaxy have orbiting planets. The telescope's extended mission will help scientists identify those planets that could possibly harbor life, Kepler Principle Investigator William Borucki said, according to a NASA press release.
Below are some highlights of Kepler's discoveries, ending with an animation produced in August by Alex Parker, a postdoctoral researcher in planetary science at the Harvard-Smithsonian Center for Astrophysics, showing all 2,299 Kepler planets and planet candidates discovered through Feb. 2012, represented to scale, as if they all orbited one star. The animation was posted online to Vimeo and YouTube.
This artist's conception illustrates Kepler-47, the first transiting circumbinary system — multiple planets orbiting two suns — located 4,900 light-years from Earth. The inner planet, Kepler-47b, which has a radius three times that of Earth's, orbits the pair of stars in less than 50 days. The outer planet, Kepler-47c, orbits its stars every 303 days, placing it in the habitable zone. The planet itself, however, is probably a gas giant a little larger than Neptune.(NASA/JPL-Caltech/T. Pyle)
An image showing the Milky Way region where the Kepler telescope points. Each rectangle indicates the specific region of the sky covered by each of Kepler's camera elements.(NASA/Carter Roberts-Eastbay Astronomical Society)
Artist's conception of planet Kepler-22b, a planet that orbits in the habitable-zone of its star.(NASA/Ames/JPL-Caltech)
NASA's Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet's surface, but they are relative small worlds orbiting a star like our sun.(Image credit: NASA/Ames/JPL-Caltech)
This artist's conception depicts the Kepler-10 star system, located about 560 light-years away near the Cygnus and Lyra constellations. One of it's planets, Kepler-10b, is a small, rocky planet (depicted as a dark spot against yellow sun). This planet, which has a radius of 1.4 times that of Earth's, whips around its star every 0.8 days.(NASA/Ames/JPL-Caltech)
Kepler-11 is a sun-like star around which six planets orbit. At times, two or more planets pass in front of the star at once, as shown in this artist's conception of a simultaneous transit of three planets.(NASA/Tim Pyle)
Kepler-10b is a scorched world orbiting it's sun at a distance that’s more than 20 times closer to its star than Mercury is to our sun. The daytime temperatures on the planet exceed 2,500 degrees. Intense radiation from the star has kept the planet from holding onto an atmosphere.(NASA/Kepler Mission/Dana Berry)
NASA said its orbiting Kepler telescope has spotted two planets the size of Earth orbiting another star, although both are far too hot to sustain life.
Kepler-10b orbits a star that is very similar to the sun, but is about twice as old. It’s located about 560 light years from our solar system.(NASA/Kepler Mission/Dana Berry)
Based on Kepler's measurements, scientists concluded that the planet TrES-2b reflects less than one percent of the sunlight falling on it, making it blacker than coal or any planet or moon in our solar system.(NASA/JPL-Caltech/T. Pyle)
Animation of all Kepler planets as if they orbited one star.