Study of 'twin' stars finds some of them are planet-eaters

A new study involving at least 91 pairs of twin stars has revealed that these planetary bodies, possessing matching sizes and chemical compositions, have exhibited signs of ingesting a planet.

According to the scientists, Reuters reported, the event could have occurred after the planet was sent hurtling out of a balanced orbit for any number of different reasons.

In its roughly 4.5 billion years of existence, Earth and its sibling planets, as part of the planetary system revolving around the sun, have remained stable. But this latest discovery shows that other planetary systems are not that lucky.

The study has taken a look at the pairs of stars that formed within the same interstellar cloud of gas and dust — so-called co-natal stars — giving them the same chemical makeup, and were of roughly equal mass and age. These are the "twins." While the pairs move in the same direction within our Milky Way galaxy, they are not binary systems of two stars gravitationally bound to each other.

A star's chemical composition changes when it engulfs a planet because it incorporates the elements that make up the doomed world. The researchers looked for stars that differed from their twin because they had higher amounts of tell-tale elements like iron, nickel or titanium indicating remnants of a rocky planet, relative to certain other elements.

"It's the elemental abundance differences between two stars in a co-natal system," said astronomer Fan Liu of Monash University in Australia, lead author of the study published in the journal Nature.

In seven of the pairs, one of the two stars bore evidence of planetary ingestion.

Possible reasons for a planet making a death plunge into its host star include an orbital disturbance caused by a larger planet, or another star passing uncomfortably close, destabilizing the planetary system, the researchers said.

"This really puts into perspective our fortuitous position in the universe," said astrophysicist and study co-author Yuan-Sen Ting of the Australian National University and Ohio State University. "The stability of a planetary system like the solar system is not a given."