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Latest Kepler find more than doubles number of known exoplanets

This artist's concept depicts select planetary discoveries made to date by NASA's Kepler space telescope. Image Credit: NASA/W. Stenzel

This artist’s concept depicts select planetary discoveries made to date by NASA’s Kepler space telescope. (Click for full view) Image Credit: W. Stenzel / NASA

Scientists with NASA’s planet-hunting Kepler mission announced on Tuesday, May 10 that they have verified 1,284 new exoplanets—the largest single finding to date. The newly-verified worlds were among 4,302 candidates in the Kepler space telescope’s July 2015 catalog. 

“This announcement more than doubles the number of confirmed planets from Kepler,” Ellen Stofan, chief scientist at NASA Headquarters in Washington, said in a news release. “This gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth.”


The new statistical validation technique enables researchers to quantify the probability any given candidate signal is caused by a planet, without any follow-up observations. Image & Caption Credit: NASA Ames

The researchers published the results of their analysis in the May 10, 2016, issue of The Astrophysical Journal. 

For an object detected by Kepler to be confirmed as a planet, the probability of it being one had to be over 99 percent. In addition to the 1,284 confirmed by the analysis, 1,327 candidates were considered likely to be planets but did not meet the 99 percent threshold and 707 were more likely to be some other kind of astrophysical phenomena.

“Before the Kepler space telescope launched, we did not know whether exoplanets were rare or common in the galaxy,” said Paul Hertz, Astrophysics Division director at NASA Headquarters. “Thanks to Kepler and the research community, we now know there could be more planets than stars.”

Hertz said this knowledge will inform the future missions that are needed get closer to finding out whether or not humanity is alone in the universe.

The way Kepler finds stars is by watching for decreases in brightness. This occurs when a planet passes in front of its host star—much like the recent May 9 Mercury transit across the Sun.

The new planets are not from the ongoing K2 extended mission, however. This latest batch of verified worlds are the result of a statistical analysis method that is applied to many planet candidates simultaneously, as opposed to the process of verifying each candidate one-by-one.


Kepler has discovered 21 planets less than twice the size of Earth orbiting inside a star’s habitable zone. The orange spheres represent the nine newly validated planets, whereas the blue discs represent the 12 previously known. Image Credit: NASA Ames

Timothy Morton, an associate research scholar at Princeton University in New Jersey as well as the lead author of the paper published in The Astrophysical Journal, assigned each candidate a “planet-hood probability percentage”. According to the report, it is the first automated computation on this scale. Previous techniques focused only on sub-groups within a greater list of candidates found by Kepler.

“Planet candidates can be thought of like bread crumbs,” Morton said. “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.”

Of the more than 1,200 newly-validated planets, nearly 550 of them are thought to be terrestrial worlds like Earth, based on their size. Only nine of them orbit in the star’s habitable zone—a distance where liquid water could be expected to pool on the surface—bringing the total known exoplanets in this group to 21.

Natalie Batalha, co-author of the paper and Kepler mission scientist at NASA’s Ames Research Center in California, said the results of the analysis allow scientists to do probabilities on how many candidate planets will actually be verified as one.

“This work will help Kepler reach its full potential by yielding a deeper understanding of the number of stars that harbor potentially habitable, Earth-sized planets—a number that’s needed to design future missions to search for habitable environments and living worlds,” Batalha said.

Kepler was launched in March 2009. It is the first NASA mission dedicated to finding potentially habitable Earth-sized planets. For the first number of years of operation, the telescope was pointed toward a small patch of sky to monitor about 150,000 stars at once.

In 2018, NASA plans to launch the Transiting Exoplanet Survey Satellite (TESS). It will use the same transiting method to monitor 200,000 nearby stars—looking for the tiny dip in brightness. TESS will be focused on searching for Earth and Super-Earth-size planets.

Video courtesy of NASA


Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.

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