Planet-eating suns spotted by Aussie scientists

Twin stars should be identical, but sometimes one is hungrier than its sibling.

An international research team led by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (or ‘ASTRO 3D’) – a collaboration between three Australian universities – has found that in 8% of stellar twins that one of the pair eats through nearby planets.

Using the Magellan Telescope and Very Large Telescope in Chile, and the Keck Telescope in Hawaii, the research group expected to find twin stars to have identical composition, given they form from the same material clouds in space.

But about 7 of the 91 pairs monitored have differences. It’s noteworthy because unlikely end-of-life stars that expand and consume planets during this process,  these are ‘prime of life’ main sequence stars.

That means the ASTRO 3D group’s findings are different to similar evidence of planet-eating stars published last month. In that research, a team from the European Southern Observatory spotted metallic ‘scarring’ on the surface of a white dwarf, believed to be from a 500km-wide planet being ripped apart during the star’s expansive red giant stage.

“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,” says Fan Liu, the project lead.

While Liu acknowledges the chemical composition could be the result of a star collecting ‘planetary material’ (building blocks for a planet) his group favours a theory that the whole planet has been consumed by these suns – the final cake, rather than the ingredients.

“It’s complicated,” Liu says.

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

The research is published in the journal Nature.