Washington, Sept 05 (ANI): Researchers at The University of Texas at Austin have discovered an unusual multiple-planet system containing a super-Earth and two Neptune-sized planets orbiting in resonance with each other using NASA's planet hunting Kepler Space Telescope.
Lead researcher Bill Cochran and his team are announcing three planets orbiting Kepler-18, a star similar to the Sun. The planets are designated b, c, and d.
All three planets orbit much closer to Kepler-18 than Mercury does to the Sun.
Orbiting closest to Kepler-18 with a 3.5-day period, planet b weighs in at about 6.9 times the mass of Earth, and twice Earth's size. Planet b is considered a "super-Earth." Planet c has a mass of about 17 Earths, is about 5.5 times Earth's size, and orbits Kepler-18 in 7.6 days. Planet d weighs in at 16 Earths, at 7 times Earth's size, and has a 14.9-day orbit.
The masses and sizes of c and d qualify them as low-density "Neptune-class" planets.
Planet c orbits the star twice for every one orbit d makes. But the times that each of these planets transit the face of Kepler-18 "are not staying exactly on that orbital period," Cochran says.
"One is slightly early when the other one is slightly late, [then] both are onime at the same time, and then vice-versa," he added.
Scientifically speaking, c and d are orbiting in a 2:1 resonance.
"It means they're interacting with each other," Cochran explains.
"When they are close to each other they exchange energy, pull and tug on each other," he added.
Cochran said his team used a technique called "validation," instead of "verification", to figure out the probability that it could be something other than a planet.
They calculated that the likelihood the object is a planet is 700 times more likely than the likelihood that it's a background object.
Cochran said that it's important to understand the difference - not only for this system, but also for future discoveries from Kepler and other missions.
The research will be published in a special Kepler issue of The Astrophysical Journal Supplement Series in November. (ANI)
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