This artist's concept depicts select planetary discoveries made to date by NASA's Kepler space telescope
Credits: NASA/W. Stenzel
NASA's Kepler mission has verified 1,284 new planets – the single largest finding of planets to date.
“This announcement more than doubles the number of confirmed planets
from Kepler,” said Ellen Stofan, chief scientist at NASA Headquarters in
Washington. “This gives us hope that somewhere out there, around a star
much like ours, we can eventually discover another Earth.”
Analysis was performed on the Kepler space telescope’s July 2015
planet candidate catalog, which identified 4,302 potential planets. For
1,284 of the candidates, the probability of being a planet is greater
than 99 percent – the minimum required to earn the status of “planet.”
An additional 1,327 candidates are more likely than not to be actual
planets, but they do not meet the 99 percent threshold and will require
additional study. The remaining 707 are more likely to be some other
astrophysical phenomena. This analysis also validated 984
candidates previously verified by other techniques.
"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 Headquarters.
"This knowledge informs the future missions that are needed to take us
ever-closer to finding out whether we are alone in the universe."
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. Since the discovery of the first planets outside our solar
system more than two decades ago, researchers have resorted to a
laborious, one-by-one process of verifying suspected planets.
This latest announcement, however, is based on a statistical analysis
method that can be applied to many planet candidates simultaneously.
Timothy Morton, associate research scholar at Princeton University in
New Jersey and lead author of the scientific paper published in The
Astrophysical Journal, employed a technique to assign each Kepler
candidate a planet-hood probability percentage – the first such
automated computation on this scale, as previous statistical techniques
focused only on sub-groups within the greater list of planet candidates
identified by Kepler.
"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."
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 exclusive group.
"They say not to count our chickens before they're hatched, but
that's exactly what these results allow us to do based on probabilities
that each egg (candidate) will hatch into a chick (bona fide planet),"
said Natalie Batalha, co-author of the paper and the Kepler mission
scientist at NASA's Ames Research Center in Moffett Field, California.
“This work will help Kepler reach its full potential by yielding a
deeper understanding of the number of stars that harbor potentially
habitable, Earth-size planets -- a number that's needed to design future
missions to search for habitable environments and living worlds.”
Of the nearly 5,000 total planet candidates found to date, more than
3,200 now have been verified, and 2,325 of these were discovered by
Kepler. Launched in March 2009, Kepler is the first NASA mission to find
potentially habitable Earth-size planets. For four years, Kepler
monitored 150,000 stars in a single patch of sky, measuring the tiny,
telltale dip in the brightness of a star that can be produced by a
transiting planet. In 2018, NASA’s Transiting Exoplanet Survey Satellite
will use the same method to monitor 200,000 bright nearby stars and
search for planets, focusing on Earth and Super-Earth-sized.
Ames manages the Kepler missions for NASA’s Science Mission
Directorate in Washington. The agency’s Jet Propulsion Laboratory in
Pasadena, California, managed Kepler mission development. Ball Aerospace
& Technologies Corporation operates the flight system, with support
from the Laboratory for Atmospheric and Space Physics at the University
of Colorado in Boulder.
For more information about the Kepler mission, visit: http://www.nasa.gov/kepler
For briefing materials from Tuesday’s media teleconference where the new group of planets was announced, visit: http://www.nasa.gov/feature/ames/kepler/briefingmaterials160510
Felicia Chou
Headquarters, Washington
202-358-0257
felicia.chou@nasa.gov
Michele Johnson
Ames Research Center, Moffett Field, Calif.
650-604-6982
michele.johnson@nasa.gov
Editor: Karen Northon
Source: NASA/Kepler and K2
