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| [PHOTO: JD Hancock/CC BY 2.0] |
Washington: NASA's Kepler mission has announced the discovery of 461
new planet candidates. Four of the potential new planets are less than twice
the size of Earth and orbit in their sun's "habitable zone," the
region in the planetary system where liquid water might exist on the surface of
a planet.
Based on observations
conducted from May 2009 to March 2011, the findings show a steady increase in
the number of smaller-size planet candidates and the number of stars with more
than one candidate.
"There is no
better way to kickoff the start of the Kepler extended mission than to discover
more possible outposts on the frontier of potentially life bearing
worlds," said Christopher Burke, Kepler scientist at the SETI Institute in
Mountain View, Calif., who is leading the analysis.
Since the last Kepler
catalog was released in February 2012, the number of candidates discovered in
the Kepler data has increased by 20 percent and now totals 2,740 potential
planets orbiting 2,036 stars. The most dramatic increases are seen in the
number of Earth-size and super Earth-size candidates discovered, which grew by
43 and 21 percent respectively.
The new data
increases the number of stars discovered to have more than one planet candidate
from 365 to 467. Today, 43 percent of Kepler's planet candidates are observed
to have neighbor planets.
"The large
number of multi-candidate systems being found by Kepler implies that a
substantial fraction of exoplanets reside in flat multi-planet systems,"
said Jack Lissauer, planetary scientist at NASA's Ames Research Center in
Moffett Field, Calif. "This is consistent with what we know about our own
planetary neighborhood."
The Kepler space
telescope identifies planet candidates by repeatedly measuring the change in
brightness of more than 150,000 stars in search of planets that pass in front,
or "transit," their host star. At least three transits are required
to verify a signal as a potential planet.
Scientists analyzed
more than 13,000 transit-like signals to eliminate known spacecraft
instrumentation and astrophysical false positives, phenomena that masquerade as
planetary candidates, to identify the potential new planets.
Candidates require
additional follow-up observations and analyses to be confirmed as planets. At
the beginning of 2012, 33 candidates in the Kepler data had been confirmed as
planets. Today, there are 105.
"The analysis of
increasingly longer time periods of Kepler data uncovers smaller planets in
longer period orbits-- orbital periods similar to Earth's," said Steve
Howell, Kepler mission project scientist at Ames. "It is no longer a
question of will we find a true Earth analogue, but a question of when."
The complete list of
Kepler planet candidates is available in an interactive table at the NASA
Exoplanet Archive. The archive is funded by NASA's Exoplanet Exploration
Program to collect and make public data to support the search for and
characterization of exoplanets and their host stars.