Further observations will be required to determine which worlds are rocky like Earth and which have thick gaseous atmospheres like Neptune.
Planetary systems with TTVs can be verified without requiring extensive ground-based observations, accelerating confirmation of planet candidates. The TTV detection technique also increases Kepler’s ability to confirm planetary systems around fainter and more distant stars. Five of the systems (Kepler-25, Kepler-27, Kepler-30, Kepler-31, and Kepler-33) contain a pair of planets where the inner world orbits the star twice during each orbit of the outer body. Four of the systems (Kepler-23, Kepler-24, Kepler-28, and Kepler-32) contain a pairing where the outer planet circles the star twice for every three times the inner one completes an orbit. “These configurations help to amplify the gravitational interactions between the planets, similar to how my sons kick their legs on a swing at the right time to go higher,” said Jason Steffen from Fermilab Center for Particle Astrophysics in Batavia, Illinois. Kepler-33, a star that is older and more massive than our Sun, had the most planets. The system hosts five planets, ranging in size from 1.5 to 5 times that of Earth. All of the planets are located closer to their star than any planet is to our Sun. The properties of a star provide clues for planet detection. The decrease in the star’s brightness and duration of a planet transit, combined with the properties of its host star, present a recognizable signature. When astronomers detect planet candidates that exhibit similar signatures around the same star, the likelihood of any of these planet candidates being a false positive is very low. “The approach used to verify the Kepler-33 planets shows the overall reliability is quite high,” said Jack Lissauer from NASA’s Ames Research Center at Moffett Field, California. “This is a validation by multiplicity.” |
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