[UPDATED! Jan. 9, 2013; “First habitable zone super Earth may have been found”, see note below] Today marked the commencement of the 221st American Astronomical Society meeting, and members of the Kepler Space Telescope team had an exciting number to share: 461. That’s the number of new candidate exoplanets found by the Kepler telescope in the past year — bringing the total number of exoplanet candidates identified by Kepler to 2,740 since its mission began in March of 2009 (note: only 105 of these have been confirmed, but scientists anticipate more than 90% will eventually be confirmed)
What is even more exciting is that, of this total, 351 are Earth-size planets.Most of these are “super Earths” (planets that are more than twice the size of Earth), but four of them are less than twice the size of Earth and also orbit within the habitable (“Goldilocks”) zone where liquid water is possible.
In February of 2012, Kepler’s catalog of potential planets numbered 2,192. This new tally is an increase of 20%, with the largest increase being discoveries of Earth-size and Super Earth-size candidates (43% and 21% respectively).
A majority of the found exoplanets were solitary ones (so far) orbiting a total of 2,036 stars. However, detecting small planets can be tricky (and there are many false signals), so sometimes additional planets are found around formerly surveyed stars — proving the value of always taking a second (or third) look.
Indeed, the new tally of planets increases the number of stars with more than one planet orbiting them from 365 to 467. Of Kepler’s planet total, 43% are believed to have neighboring planets.
“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.”
Kepler finds planets using the transit method, that is, by detecting the slight dimming of a star’s brightness due to a planet transiting between the star and us. That alone is not sufficient to claim a discovery; at least three such possible transits must be observed before scientists take a closer look and conduct further analysis.
In this most recent tally, astronomers had to sort through some 13,000 potential transit signals in order to eliminate false signals caused by spacecraft instrumentation or other space phenomena. In a process much like panning for gold, over150,000 stars were surveyed to find those 13,000 possible transits, to yield just 461 likely new candidates
“The large number of multi-candidate systems being found by Kepler implies that a substantial fraction of exoplanets reside in flat multi-planet systems. This is consistent with what we know about our own planetary neighborhood.” stated Jack Lissauer, planetary scientist at NASA’s Ames Research Center, also in Mountainview (at Moffett Field), California.
This all adds up to hopeful prospects for future Kepler discoveries. As Kepler data accumulates, more potential candidates — including smaller planets like ours –– could be identified hiding in all that data.
According to Steve Howell, Kepler mission project scientist at Ames, “The analysis of increasingly longer time periods of Kepler data uncovers smaller planets in longer period orbits– orbital periods similar to Earth’s. It is no longer a question of will we find a true Earth analogue, but a question of when.”
The volume of space encompassed by Kepler’s search mission is actually quite small (see diagram, above) and its discoveries represent but a tiny fraction of what is probably out there waiting to be discovered by other telescopes — just in our galaxy.
UPDATE (Jan. 9, 2013) – Amongst the 461 new candidate planets found by the Kepler mission last year and announced at this week’s AAS meeting was the candidate planet KOI 172.02 (KOI stands for Kepler Object of Interest). If confirmed, this will be the first habitable-zone super Earth found (at 1.5 Earth masses) around a sun-type star. The discovery was announced at the meeting Monday (Jan. 7) by Christopher Burke of the SETI Institute.
If you would like to learn more about Kepler’s and/or view its complete catalog of exoplanets, an interactive table is available at the NASA Exoplanet Archive.The archive is 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.
More information about the hunt for exoplanets and the agencies/orgs that support it (courtesy of the Citizens in Space blog):
Ames manages Kepler’s ground system development, mission operations and science data analysis. NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., managed Kepler mission development. Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with JPL at the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.
The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data. Kepler is NASA’s 10th Discovery Mission and is funded by NASA’s Science Mission Directorate at the agency’s headquarters in Washington.
JPL manages NASA’s Exoplanet Exploration Program. The NASA Exoplanet Archive is hosted at the Infrared Processing and Analysis Center at the California Institute of Technology.
Source:material for this post came from the Citizens in Space blog post Kepler Has Discovered 2740 Possible Planets
Top Image: (Artist’s impression of the Kepler telescope); NASA/Ames/JPL-Caltech