Bertram Bitsch, Professor of Astrophysics at at University College Cork who has co-authored a paper that suggests that differences in stars once thought to be identical may be explained by one of the stars ingesting entire planets. Photo: Ruben Tapia/UCCTV.

Stars in their eyes!

One of these things is not like the other! Details of a new study, which UCC was involved in, were released yesterday, Wednesday, showing how an international team of astrophysicists uncovered that co-moving stars thought to be identical to their twins have differences.

These differences might have occurred already during their birth when the stars accumulate material from their surrounding discs, but it seems more likely that one star of the pair ingested planets, challenging the understanding of planetary systems.

The study, the cover story on this week's issue of academic journal Nature, with a Cork connection delves into the findings derived from data collected with the 6.5 metre Magellan Telescopes in Chile and the WM Keck Observatory. The data was also collected from the European Southern Observatory’s Very Large Telescope.

The research sheds light on a celestial phenomenon where binary co-moving stars, once thought to be identical twins due to their shared molecular origins, show subtle compositional differences, hinting at the absorption of planets.

Stars can ingest planets when gravitational interactions with other celestial bodies cause the planets to be pulled into the star's vicinity. The star's gravitational forces then lead to the ingestion of the planets, influencing the star's composition.

Bertram Bitsch, Professor of Astrophysics at the College of Science, Engineering and Food Science at UCC, is co-author of the paper along with colleagues based in Australia, Germany, Hungary and the US.

Prof. Bitsch said: “Co-moving stars come from the same molecular cloud, indicating that they should have the same composition, similar to identical twins. Stars consist mostly of hydrogen and helium; they also contain all other elements like iron, silicate, magnesium, oxygen, and carbon, which are the materials that form terrestrial planets like our own Earth.

“However, detailed new high-precision observations of these stars have revealed small compositional differences between co-moving pairs, indicating that another effect is at play. The measured compositional differences in the different elements could be attributed to differences in their accretion history during the protoplanetary disc phase of the first few millions of years of their life, but this is unlikely considering that the star evolved for billions of years afterwards, wiping out these differences.

“It seems more likely that one of the components of the co-moving pair ingested planets, giving important constraints on the stability of planetary systems around stars,” he said.

Dr Fan Liu, from Monash University is lead author of the paper and member of the ASTRO 3D research centre in Australia. The research focused on 91 pairs of stars with a shared origin and a well-defined selection function. It identified at least seven instances of planetary ingestion, leading to an occurrence rate of 8%. This discovery challenges previous assumptions about the stability of planetary systems around stars.