Planet-eating star shows us the future of our solar system

An international team of astronomers announced a particularly timely discovery: A star that ate one of its planets.

According to details published in the journal Astronomy & Astrophysics, the team made its conclusion based on the unusual composition of the star’s atmosphere.

The star, known as HIP68468’s, was found to contain four times more lithium than might be predicted in a star that is 6 billion years old, along with an excess of refractory elements, or metals resistant to heat and that are very common in rocky planets.

Inside stars like HIP68468 and our Sun, lithium is used up over time. Planets, conversely, preserve lithium because their internal temperatures are not sufficient to destroy the element. Consequently, when a star absorbed a planet, the lithium from the planet in the stellar atmosphere becomes very apparent to scientists.

Massive Planet Absorbed

The study team said the amount of lithium seen in HIP68468 is equivalent to the mass of six Earths.

“It can be very hard to know the history of a particular star, but once in a while we get lucky and find stars with chemical compositions that likely came from in-falling planets,” Debra Fischer, a professor of astronomy at Yale University who was not involved in the research, said in a news release. “That’s the case with HD68468. The chemical remains of one or more planets are smeared in its atmosphere.

“It’s as if we saw a cat sitting next to a bird cage,” she added. “If there are yellow feathers sticking out of the cat’s mouth, it’s a good bet that the cat swallowed a canary.”

Using the 3.6-meter telescope at La Silla Observatory in Chile, researchers found the first exoplanet orbiting HIP68468 in 2015. More recently, scientists have also found evidence of two more planets orbiting the star: a super Neptune and a super Earth. Their orbits are remarkably close to their host star, with one 50 percent bigger than Neptune and situated at a Venus-like range from its star. The other is thought to have triple the Earth’s mass and an orbit so close, it takes just three days to circle its host.

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Image credit: Gabi Perez / Instituto de Astrofísica de Canarias

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