“It’s a bit like when you take Play-Doh and you squeeze it continuously at some point it gets warm,” Benneke said. As it gets closer, a gravitational squeeze deforms the planet, creating internal friction and heating things up from the inside, a process called tidal heating. As it travels along its elliptical orbit, which takes an average of 66 hours, its distance to the star varies slightly. LP 791-18 d is a rocky planet with a mass and density similar to those of Earth. The researchers reported their findings in Nature. Every rendezvous, planet c gives its smaller sibling a gravitational tug that further elongates its orbit, scrambling the timing of the smaller planet’s transits in the process. At their closest approach, the planets are only 1.5 million kilometers apart, about 4 times the distance between the Earth and the Moon. LP 791-18 d is nestled between the system’s two other planets and has an elliptical orbit that takes it very close to the outer and larger planet (LP 791-18 c). Get the most fascinating science news stories of the week in your inbox every Friday.Įventually, they unraveled the mystery. “There were several months we were worried that we couldn’t confirm that the planet was even real.” This newsletter rocks. “One of the challenges, and this is why we can also now say that there is volcanism, is that we couldn’t find the planet at the time that we predicted,” Benneke said. But subsequent transits never arrived on time. “There were several months we were worried that we couldn’t confirm that the planet was even real.”Īt least two transits are necessary to determine a planet’s orbital period and gauge its mass and density, so Benneke and his colleagues monitored the planet with several ground-based observatories. After staring at it for five consecutive days, Spitzer detected a new Earth-sized planet crossing in front of the star-transiting, in astronomical lingo. The finding comes after a group of researchers led by astrophysicist Björn Benneke of the Université de Montréal in Canada used NASA’s recently retired Spitzer Space Telescope to take a closer look at the system. The exoplanet, known as LP 791-18 d, orbits a red dwarf already known to host two other planets: LP 791-18 b, a scorched, rocky world orbiting extremely close to the star, and LP 791-18 c, a sub-Neptune 7 times more massive than Earth made of gas or icy material. An unusual planetary dance has produced an Earth-sized exoplanet brimming with volcanoes, likely furnished with an atmosphere, and maybe even containing water on its surface.Īstronomers discovered this odd world orbiting a red dwarf star right in our galactic neighborhood-just 90 light-years away.
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