A new analysis of data collected during the Kepler space telescope's prime planet-hunting mission shows that 1,284 candidate planets are indeed confirmed exoplanets, boosting the current tally of worlds beyond the solar system to 3,264.
Kepler, which was launched in 2009, is responsible for the bulk of the sightings, but confirmation of its detections with ground-based observatories has been a time-consuming, tedious and difficult process.
Now, a team of astronomers, led by Princeton University's Tim Morton, has developed a new type of statistical analysis that can assess many planet candidates simultaneously.
"Imagine planet candidates as bread crumbs," Morton told reporters on a conference call Tuesday.
"If you drop a few large pieces of bread on the ground, you can pick them up individually one by one ... But, if you spill a whole bucketful of small crumbs, you're going to need a broom to clean them up.
"Our broom here is a new analysis technique that enables us to quantify the probability that any given signal is in fact caused by planet, without requiring any follow-up observations," Morton said.
Kepler spent more than four years staring at the light coming from about 150,000 target stars. Scientists then combed the data searching for slight changes in the amount of light that may be caused by orbiting planets passing by, relatively to the telescope's line of sight.
Since binary stars and other phenomena also can temporarily and repeatedly dim starlight, scientists have had to get time on ground-based telescopes for follow-on observations.
The new technique uses detailed simulations of what starlight dimmed by transiting planets looks like and what starlight dimmed by other phenomena looks light. It then combines that analysis with how likely it is that another condition, such as a binary star, is present and then rates the candidates on a scale of zero to one.
Candidates with a score of more than 99 percent are considered validated planets, Morton said.
Astronomers practiced using the technique on 984 Kepler planets that were previously confirmed by other methods and found it matched, he added.
Nine of the newly classified planets are believed to be rocky worlds orbiting their parent stars at the right distances for liquid surface water, a condition that scientists believe bolsters the chance for life.
The analysis technique showed that an additional 1,327 candidates are more likely than not to be actual planets, but they did not meet the 99 percent threshold and will require additional study, NASA said.
The remaining 707 Kepler planet candidates are more likely to be some other astrophysical phenomena.
The research is published in the current edition of The Astrophysical Journal.