Star swallowed planet

The engulfment of a planet by its host star. Gabi Perez / IAC

Swiss astronomers, working as part of an international team, have found evidence that Sun-like stars can devour or swallow the planets in orbit around them.

The scientists have detected an isotope, lithium-6, in the atmosphere of a star, which is destroyed in the early stages of stellar evolution but is preserved in planets.

“The most credible explanation is that some planet or at least some planetary material fell into the star at some time in its history,” said Nuno Santos of the Geneva Observatory.

The star (HD82943) lies about 90 light-years away. It is very similar to the Sun, but slightly larger and brighter.

HD82943 has two planets in orbit around it. Extrasolar planets – that’s to say planets outside our solar system – have puzzled astronomers because they orbit very close to their parent stars in regions of space where they could not possibly have formed.

“They were formed further away from the star and then they migrated inwards,” said Santos. “During this process, we believe the planet may eventually fall into the star and we are finding evidence to this effect.”

Some 63 extrasolar planetary systems have so far been discovered. Santos said it was too early to say if our solar system was unusual but the new planets differed in key respects from similar giant planets like Jupiter.

“Not only are they very close to the star or relatively close compared to Jupiter’s distance from the sun but they also tend to have eccentric orbits unlike solar system planets which have almost circular orbits around the sun.

“We are seeing that the processes which lead to the formation of planets are much more complicated than we thought.”

by Vincent Landon