NASA’s planet hunting space telescope Kepler added a record 1,284 confirmed planets to its already impressive discoveries of extraterrestrial worlds.
This batch of planets is the largest single account of new planets since Kepler launched in 2009 and more than doubles the number of confirmed planets realized by the space telescope so far to more than 2,300.
"Before the Kepler space telescope launched, we did not know whether exoplanets were rare or common in the galaxy. Thanks to Kepler and the research community, we now know there could be more planets than stars,” said Paul Hertz, Astrophysics Division director at NASA. "This knowledge informs the future missions that are needed to take us ever-closer to finding out whether we are alone in the universe."
The discoveries are a result of a technique developed at Princeton that lets scientists analyze thousands of signals Kepler has identified to determine which are most likely to be caused by planets and which are caused by non-planetary objects such as stars. This automated technique -- reported in The Astrophysical Journal on May 10 and implemented in a publicly available custom software package called Vespa -- computes the chances that the signal is in fact caused by a planet, the researchers said.
Kepler captures the discrete signals of distant planets – decreases in brightness that occur when planets pass in front of, or transit, their stars – much like the May 9 Mercury transit of our sun, NASA said.
“Vespa computed the reliability values for over 7,000 signals identified in the latest Kepler catalog which identified 4,302 potential planets and verified the 1,284 planets with 99% certainty. They also independently verified more than 700 additional planet signals that had already been confirmed as planets by other methods. In addition, the researchers identified 428 candidates as likely “false positives,” or signals generated by something other than a planet,” the Princeton researchers said.
"Planet candidates can be thought of like bread crumbs,” said Morton. “If you drop a few large crumbs on the floor, you can pick them up one by one. But, if you spill a whole bag of tiny crumbs, you're going to need a broom. This statistical analysis is our broom."
According to NASA, in the newly validated batch of planets, nearly 550 could be rocky planets like Earth, based on their size. Nine of these orbit in their sun's habitable zone, which is the distance from a star where orbiting planets can have surface temperatures that allow liquid water to pool. With the addition of these nine, 21 exoplanets now are known to be members of this select group.
The fact that Kepler is still operating is amazing. Kepler you may recall was rendered inoperable after the second of four gyroscope-like reaction wheels, which are used to precisely point the spacecraft for extended periods of time, failed in 2103 ending data collection for the original mission. The spacecraft required three working wheels to maintain the precision pointing necessary to detect the signal of small Earth-sized exoplanets orbiting stars like our sun in habitable zone -- the range of distances from a star where the surface temperature of a planet might be suitable for liquid water, NASA stated.
NASA Kepler and Ball Aerospace engineers say they have developed a way of recovering this pointing stability by maneuvering the spacecraft so that solar pressure - the pressure exerted when the photons of sunlight strike the spacecraft -- is evenly distributed across the surfaces of the spacecraft. NASA says by orienting the spacecraft nearly parallel to its orbital path around the sun, which is slightly offset from the ecliptic, the orbital plane of Earth, it can achieve spacecraft stability. The ecliptic plane defines the band of sky in which lie the constellations of the zodiac.
With a couple glitches – one recently that saw Kepler go into Emergency mode—the K2 system as it is known, has performed well and continues to send back myriad details of the little patch of space it watches.
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