Planetary scientists have announced the first discovery of a system in which an exoplanet is spiraling towards its star. "Hot Jupiter" Kepler-1658b, 2,600 light years from Earth, is being affected by tidal forces and will be destroyed by a collision with a star, scientists believe.
Measuring the orbital decay of exoplanets is a very difficult task, scientists say. The process is very slow and gradual. For example, the orbital period of Kepler-1658b is decreasing at a rate of only about 131 ms per year.
"If it continues spiralling towards its star at the observed rate, the planet will collide with its star in less than three million years," said Shreyas Vissapragada, a postdoc at the Harvard-Smithsonian Center for Astrophysics and the study's lead author. "This is the first time we've observed direct evidence for a planet spiralling towards its evolved star."
Detecting this decrease took 13 years of careful observation with three telescopes. The researchers used the Kepler Space Telescope, instruments from the Palomar Observatory in Southern California, and the Transiting Exoplanet Survey Satellite (TESS) to record the transit of the planet.
Although researchers do not yet fully understand all the processes occurring in this system, the primary cause of the orbital decay experienced by Kepler-1658b is tide - the gravitational interaction between two rotating bodies (a planet and a star in this case).
A star has evolved to the point in its life cycle known as the "subgiant" phase when it starts expanding and becoming brighter. This accelerates the process of orbital decay, making it easier to study on a human time scale, the scientists note. A similar fate awaits the Sun at a certain stage in its evolution, they add:
"In five billion years or so, the Sun will evolve into a red giant star."
The fate of Earth remains unclear, since the tidally-driven processes on it might be balanced by the loss of mass from the Sun, which will save Earth from colliding with the Sun.