February 26, 2014
Today, NASA's Kepler mission announced that 715 previous exoplanet candidates are now confirmed planets. This brings the number of confirmed exoplanets to almost 1,700. Most of the new exoplanets are smaller than Neptune and closer to Earth in size. These new worlds orbit 305 stars, which means that many of them are part of solar systems with multiple planets.
Artist impression of multiple-planet systems. Credit: NASA
"The Kepler team continues to amaze and excite us with their planet hunting results," said John Grunsfeld, who is associate administrator for NASA's Science Mission Directorate in Washington, USA. "That these new planets and solar systems look somewhat like our own, portends a great future when we have the James Webb Space Telescope in space to characterize the new worlds."
First extrasolar, or exoplanets, were discovered two decades ago and since then we had less than 1,000 confirmed planets. During its operation 2009-2013, Kepler Space Observatory had spotted over 3,500 exoplanet candidates and less than 1,000 had been confirmed until today.
So, what changed?
Instead of searching for and confirming individual planets, researchers used a technique called verification by multiplicity. They concentrated their efforts on stars with multiple candidates and relied on the presumption that if the star has multiple candidates, they are probably planets and if there's only one candidate, it could be nothing or it could be a stellar partner in a binary system. This way, they could focus on 305 stars which led to confirmation of 715 new exoplanets.
"Four years ago, Kepler began a string of announcements of first hundreds, then thousands, of planet candidates – but they were only candidate worlds," said Jack Lissauer of Ames Research Center in Moffett Field, California, USA. He is the co-leader of the team. "We've now developed a process to verify multiple planet candidates in bulk to deliver planets wholesale, and have used it to unveil a veritable bonanza of new worlds."
Four of these exoplanets stand out because they are less than 2.5 times the size of Earth and orbit their host stars at distances where water is able to remain liquid and support life – so-called habitable zone. One of these planets is named Kepler-296f and it orbits a star that has 5% of Sun's brightess and half of its mass. Sounds promising!
"From this study we learn planets in these multi-systems are small and their orbits are flat and circular – resembling pancakes – not your classical view of an atom," said Jason Rowe, another co-leader of the research, of SETI Institute in Mountain View, California, USA. "The more we explore the more we find familiar traces of ourselves amongst the stars that remind us of home."
With each new discovery such as this one, we realize that our solar system is not unique and gives us hope that there are many planets on which are similar to Earth and which we could colonize one day in the distant future.