Astronomers Have Observed A Planet-Devouring Star

Gabi Perez / Instituto de Astrofísica de Canarias

Studying the Sun has allowed us to understand a lot about how stars work, but other stars also can provide clues about our hot companion. To help with that, astronomers have been studying solar twins, stars that look like our Sun.

Among these, an international team of scientists discovered a gruesome example: a planet-eating star. The object, known as HIP 68468, is orbited by two planets and is 6 billion years old, making it 20 percent older than our own Solar System. This find is reported in Astronomy & Astrophysics, and is available on arXiv.

But don’t let this star fool you. Observations show the remains of one or more planets are spread out through the star's atmosphere. The team saw refractory metals and lithium, but both – especially the lithium – should have been consumed over the star’s lifetime.

The fact that it’s still there suggests that, like a gigantic Pacman gobbling up white dots, HIP 68468 has eaten some of its planets. Based on the lithium, six Earth's worth of rocky materials were consumed. 

"This study of HIP68468 is a post-mortem of this process happening around another star similar to our sun. The discovery deepens our understanding of the evolution of planetary systems," senior author Professor Debra Fischer from Yale University said in a statement.

The system, located 300 light-years from Earth, still has two surviving exoplanets. The first one is three times the mass of Earth, and the second one is 50 percent heavier than Neptune. But while the large planets in our Solar System are located further away, these two orbit very close to their star.

The super-Earth orbits HIP 68468 in just three days, and the hot Neptune is at a Venus-like distance. These being so close, coupled with the planets already eaten by the star, indicates that a cosmic game of tug-of-war ended badly for the planets, and they have been pulled closer and closer to the star.

“These two planets most likely didn’t form where we see them today,” said Megan Bedell, a University of Chicago doctoral student, who is a co-author of the research and the lead planet finder for the collaboration.

While a planet-eating star is interesting, it doesn’t mean it will happen to our Solar System. At the same time, this is a reminder that stars are truly terrifying.

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