The first exoplanet to be discovered by the Kepler Space Telescope is doomed to be ripped apart and incinerated by its host star.
Astronomers will not be treated to a light show anytime soon, since the planet’s orbit is decaying at a rate of 131 milliseconds per year. But the planet’s slow demise gives astronomers a look into a process that is not well understood.
“We’ve previously detected evidence for exoplanets inspiraling toward their stars, but we have never before seen such a planet around an evolved star,” said Shreyas Vissapragada, a planetary astrophysicist at the Harvard and Smithsonian Center for Astrophysics, in a statement. His findings can be found in The Astrophysical Journal Letters.
“Theory predicts that evolved stars are very effective at sapping energy from their planets’ orbits, and now we can test those theories with observations,” he said.
The exoplanet is a gas giant called Kepler-1658b and is nearly six times larger than Jupiter. Astronomers call the planet a “hot Jupiter” because it has a mass and size similar to Jupiter, but much hotter. Its orbit is an eighth of the space between our Sun and Mercury, and takes less than four days to complete an orbit around the star.
Kepler-1658b’s star was first observed in 2009, but astronomers did not confirm the exoplanet’s existence until 2019. The planet orbits a star that is 2,571 light years away.
The planet’s doom is found in the same tidal forces responsible for the daily rise and fall of Earth’s oceans. Tides are the clashing gravitational forces between two orbiting bodies, such as Earth and the Moon or Kepler-1658b and its star.
This tidal force distorts each other’s shapes and releases energy. This force may also explain why Kepler-1658b is brighter than expected. This can also cause stellar bodies to be pushed away or towards each other. The Earth and Moon are slowly moving away from each other, for instance, while Kepler-1658b is slowly moving towards its star.
The star has also reached a point in its life cycle where it has started expanding into a red giant. This fate awaits our own Sun billions of years from now.
“Now that we have evidence of inspiraling of a planet around an evolved star, we can really start to refine our models of tidal physics,” said Vissapragada. “The Kepler-1658 system can serve as a celestial laboratory in this way for years to come, and with any luck, there will soon be many more of these labs.”