Stellar Drama: The Death Of Two Exoplanets
Graphical sketch of the Kepler-56 system.
Daniel Huber / NASA Ames
(Inside Science) -- In 130 to 155 million years, Earthlings might get a front-row seat to the death of not one, but two planets.
Gongji Li, a researcher at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, reported that she and her team found two exoplanets orbiting the star Kepler-56 that will soon be consumed by the expanding star.
“In terms of astrophysical time scales, this is very short. We are very fortunate to observe a system where two of its planets are going to die,” Li said on Monday during a press conference at a meeting of the American Astronomical Society in Boston.
The two planets were discovered in 2012 as part of NASA’s exoplanet-searching Kepler Mission . The planets, named Kepler 56B and Kepler 56C are about the sizes of Neptune and Saturn, respectively. But these gas giants both orbit closer to their star than Mercury orbits to the sun. Their home star is slightly larger than the sun and is part of the Cygnus constellation , 2,800 light years from our solar system.
Additionally, the star is in a late stage of life where it’s slowly expanding outward and will soon engulf the two planets.
As this star expands and devours Kepler 56B and C, it will give us some sense of what will become of the Earth when the sun expands and surrounds our planet in about 5 billion years.
Li and her team estimated the death of these two planets in 130-155 million years by calculating the rate of the star’s expansion and the point at which the star’s tidal force (gravitational pull) on the planets will overwhelm them, drawing them into the star’s mass.
Li also said in the press conference that — assuming life on Earth is still around to see the planets die — it will be exciting to see what, if anything, is left behind. Li wondered if the planet’s core might remain after the star dies, and if it will then become a rogue planet – doomed to wander the galaxy without a host star forevermore.
Cynthia McKelvey is a science writer based in Santa Cruz, California. She tweets @NotesofRanvier
