A research published in Nature today indicates that at least one in a dozen stars exhibit signs of planetary swallowing.

The multinational research team looked at twin stars with similar compositions. However, they differ in roughly 8% of situations, which confuses astronomers.

The team, under the direction of ASTRO 3D scientists, has discovered that one of the twins’ consumption of planets or planetary debris is the cause of the discrepancy.

The results are the result of a substantial dataset obtained with the 10-meter Keck Telescope in Hawaii, United States, and the 6.5-meter Magellan Telescope and the Very Large Telescope of the European Southern Observatory, both in Chile.

“We looked at twin stars traveling together. They are born of the same molecular clouds and so should be identical,” according to ASTRO 3D researcher and report main author Dr. Fan Liu of Monash University.

“Thanks to this very high precision analysis, we can see chemical differences between the twins. This provides very strong evidence that one of the stars has swallowed planets or planetary material and changed its composition.”

Approximately 8% of the 91 pairs of twin stars that the scientists examined exhibited the phenomena. The fact that the stars in this study were so-called main sequence stars, as opposed to stars in their terminal stages like red giants, is what makes it so interesting.

“This is different from previous studies where late-stage stars can engulf nearby planets when the star becomes a very giant ball,” Dr. Liu explains.

Although it’s unclear if the stars are consuming protoplanetary material or entire planets, Dr. Liu believes both scenarios are plausible.

“It’s complicated. The ingestion of the whole planet is our favored scenario but of course we can also not rule out that these stars have ingested a lot of material from a protoplanetary disk,” he says.

The results have broad implications for the investigation of planetary systems’ long-term evolution.

“Astronomers used to believe that these kinds of events were not possible. But from the observations in our study, we can see that, while the occurrence is not high, it is actually possible. This opens a new window for planet evolution theorists to study,” adds co-author and Australian National University (ANU) Associate Professor Yuan-Sen Ting, an ASTRO 3D researcher.

The study is a component of a larger effort led by Liu, Ting, and Associate Professor David Yong (also with ASTRO 3D at ANU), called the Complete Census of Co-moving Pairs of Objects (C3PO) initiative, which aims to spectroscopically observe a complete sample of all bright co-moving stars identified by the Gaia astrometric satellite.

“The findings presented here contribute to the big picture of a key ASTRO 3D research theme: the chemical evolution of the universe. Specifically, they shed light on the distribution of chemical elements and their subsequent journey, which includes being consumed by stars,” according to Professor Emma Ryan-Weber, Director of ASTRO 3D.

Participating in the study were scientists from the Max Planck Institute for Astronomy, Ohio State University, Ohio State University, Hungarian Konkoly Observatory, Swinburne University of Technology in Australia, and University College Cork in Ireland.

When twin stars are carried in the same molecular clouds and move together, they are referred to be co-natal twins. Although several pairs of them were, they are not invariably binary stars.