Astronomers Identify Sun-Like Stars that Eat Earth-Like Planets

Astronomers have found that some sun-like stars have the ability to consume Earth-like planets. During their developmental stages, these sun-like stars swallow large amounts of rocky material, from which small, rocky planets such as Earth, Venus and Mars are formed.

A graduate student in astronomy from Vanderbilt University, Trey Mack, has developed a model that has the capability to estimate the effects of huge diet on the chemical composition of the star. To analyse this, he used a pair of twin stars that have their own planets.

"Trey has shown that we can actually model the chemical signature of a star in detail, element by element, and determine how that signature is changed by the ingestion of Earthlike planets. We can actually see the signature predicted by our model, in detail, element by element," said Keivan Stassun, Vanderbilt Professor of Astronomy, who supervised the study.

This ability will help astronomers' to understand the planet formation process, along with the current search for Earth-like planets, according to the astronomers.

Since long, astronomers have been detecting extrasolar planets in huge numbers. Since planets are proportionally richer in elements heavier than helium as compared to stars, absorbtion increases the metallicity of the stars and according to some theories, high metallicity stars are likely to have planets.

Mack chose stars, HD 20781 and 20782, unique in wide binary pair and both have planets in orbits. Both stars are of G-class like that of the sun. HD 20781 has two planets, the mass of which is similar to that of Neptune. One has a similar orbit like that of Mercury and the other much close than it. On the other hand, HD 20782 has a planet that is almost twice the Jupiter's mass.

"Imagine that the star originally formed rocky planets like Earth. Furthermore, imagine that it also formed gas giant planets like Jupiter. The rocky planets form in the region close to the star where it is hot and the gas giants form in the outer part of the planetary system where it is cold. However, once the gas giants are fully formed, they begin to migrate inward and, as they do, their gravity begins to pull and tug on the inner rocky planets. With the right amount of pulling and tugging, a gas giant can easily force a rocky planet to plunge into the star. If enough rocky planets fall into the star, they will stamp it with a particular chemical signature that we can detect," noted Mack.

However, Mack and Stassun are still uncertain if the star still hosts Earth-like planets. "When we find stars with similar chemical signatures, we will be able to conclude that their planetary systems must be very different from our own and that they most likely lack inner rocky planets," Mack explained.

The details of the study were published in the Astrophysical Journal.