November 18th, 2012 by James Ayre
NASA’s Kepler Space Telescope just finished its three-and-a-half-year primary mission, searching for Earth-like planets in the cosmos. NASA is now planning to begin its extended mission, lasting for up to four more years.
So far, data from Kepler has led to the identification of more than 2,300 new planet candidates, 100 of which have already been confirmed to be planets. Kepler has clearly shown that the galaxy is filled with planetary systems, many of which could potentially host life as we know it.
Of these planetary candidates, hundreds of them appear to be somewhat Earth-like, many orbiting within the ‘habitable zone’.
“The initial discoveries of the Kepler mission indicate at least a third of the stars have planets and the number of planets in our galaxy must number in the billions,” said William Borucki, Kepler principal investigator at NASA’s Ames Research Center in Moffett Field, Calif. “The planets of greatest interest are other Earths, and these could already be in the data awaiting analysis. Kepler’s most exciting results are yet to come.”
“NASA’s Kepler Space Telescope searches for planet candidates orbiting distant suns, or exoplanets, by continuously measuring the brightness of more than 150,000 stars. When a planet candidate passes, or transits, in front of the star from the spacecraft’s vantage point, light from the star is blocked. Different-sized planets block different amounts of starlight. The amount of starlight blocked by a planet reveals its size relative to its star.”
Launched back on March 6, 2009, Kepler’s mission was to investigate a specific portion of the galaxy, then determining what fraction of the stars that finds may potentially be habitable. The planets of primary interest were those that orbited in or near habitable zones.
“Kepler began the search for small worlds like our own on May 12, 2009, after two months of commissioning. Within months, five exoplanets, known as hot Jupiters because of their enormous size and orbits close to their stars, were confirmed.”
Kepler has greatly expanded the knowledge that humans have of planets and planetary systems throughout the galaxy. Some highlights from the prime mission are outlined below:
— In August 2010, scientists confirmed the discovery of the first planetary system with more than one planet transiting the same star. The Kepler-9 system opened the door to measurement of gravitational interactions between planets as observed by the variations in their transit timing. This powerful new technique enables astronomers, in many cases, to calculate the mass of planets directly from Kepler data, without the need for follow-up observations from the ground.
— In January 2011, the Kepler team announced the discovery of the first unquestionably rocky planet outside the solar system. Kepler-10b, measuring 1.4 times the size of Earth, is the smallest confirmed planet with both a radius and mass measurement. Kepler has continued to uncover smaller and smaller planets, some almost as small as Mars, which tells us small rocky worlds may be common in the galaxy.
— “In February 2011, scientists announced Kepler had found a very crowded and compact planetary system — a star with multiple transiting planets. Kepler-11 has six planets larger than Earth, all orbiting closer to their star than Venus orbits our sun. This and other subsequently identified compact, multi-planet systems have orbital spacing relative to their host sun and neighboring planets unlike anything envisioned prior to the mission.”
— “In September 2011, Kepler data confirmed the existence of a world with a double sunset like the one famously portrayed in the film ‘Star Wars’ more than 35 years ago. The discovery of Kepler-16b turned science fiction into science fact. Since then, the discoveries of six additional worlds orbiting double stars further demonstrated planets can form and persist in the environs of a double-star system.”
— “In December 2011, NASA announced Kepler’s discovery of the mission’s first planet in a habitable zone. Kepler-22b, about 2.4 times the size of Earth, is the smallest-radius planet yet found to orbit a sun-like star in the habitable zone. This discovery confirmed that we are getting continually closer to finding planets like our own.”
— “In February 2012, the Kepler team announced more than 1,000 new transiting planet candidates for a cumulative total of 2,321. The data continue the trend toward identifying smaller planets at longer orbital periods, similar to Earth. The results include hundreds of planetary systems.”
— “Recently, citizen scientists participating in Planet Hunters, a program led by Yale University, New Haven, Conn., that enlists the public to comb through Kepler data for signs of transiting planets, made their first planet discovery. The joint effort of amateur astronomers and scientists led to the first reported case of a planet orbiting a double star. The three bodies are, in turn, being orbited by a second distant pair of stars.”
“Kepler’s bounty of new planet discoveries, many quite different from anything found previously, will continue to astound,” said Jack Lissauer, planetary scientist at Ames. “But to me, the most wonderful discovery of the mission has not been individual planets, but the systems of two, three, even six planets crowded close to their stars, and, like the planets orbiting about our sun, moving in nearly the same plane. Like people, planets interact with their neighbors and can be greatly affected by them. What are the neighborhoods of Earth-size exoplanets like? This is the question I most hope Kepler will answer in the years to come.”
It was decided back in April that Kepler could continue on an extended mission at least as late as 2016.
Source: NASA/Jet Propulsion Laboratory
Image Credits: NASA/JPL-Caltech
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