Massive stars could 'steal' gas giants from their planetary systems

a planet with rings
An artist's depiction of a ringed exoplanet. (Image credit: Lev Savitskiy via Getty Images)

Jupiter-size planets may be snatched from their home planetary systems by massive young stars in a bold 'planetary heist.'

The findings could explain the existence of huge gas giant exoplanets — or "super-Jovian planets" — around massive, hot, young stars, which has been a mystery until now. The two recently discovered B-star Exoplanet Abundance Study (BEAST) planets are Jupiter-like planets that orbit their massive stars at great distances, hundreds of times the separation between Earth and the sun.

"The BEAST planets are a new addition to the myriad of exoplanetary systems, which display incredible diversity, from planetary systems around sun-like stars that are very different to our solar system, to planets orbiting evolved or dead stars," Richard Parker, an astrophysicist at the University of Sheffield in the U.K. and a co-author on the new research, said in a statement

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The formation of 'BEASTies' has problematic because huge stars blast out tremendous amounts of ultraviolet radiation. Scientists thought that this radiation should prevent growing planets forming around them from reaching the size of Jupiter, the largest planet in our solar system.

"Whilst planets can form around massive stars, it is hard to envisage gas giant planets like Jupiter and Saturn being able to form in such hostile environments, where radiation from the stars can evaporate the planets before they fully form," Parker added.

The new research posits that these massive BEASTies didn't form in their current systems at all but instead were snatched from around smaller stars in a stellar nursery, a region where rates of star formation are particularly high. The pair of scientists behind the work reached this conclusion by simulating the conditions in stellar nurseries, which showed that planets captured from these regions can settle into orbits similar to those of observed BEASTies.

The duo's previous research had already shown that massive stars within stellar nurseries could ensnare planets from other stars or rogue free-floating planets that do not orbit a star. But this research makes it clear these snatched worlds can become 'BEASTies.'

"Essentially, this is a planetary heist," Emma Daffern-Powell, an astronomer also at the University of Sheffield, said in the same statement. "We know that massive stars have more influence in these nurseries than sun-like stars, and we found that these massive stars can capture or steal planets — which we call 'BEASTies.'"

Daffern-Powell explains that the team's computer simulations show that the theft or capture of these BEASTies occurs on average once in the first 10 million years of the evolution of a star-forming region.

"Our results lend further credence to the idea that planets on more distant orbits more than 100 times the distance from Earth to sun may not be orbiting their parent star," Parker concluded. 

The team's research is part of a wider astronomy program that aims to discover how common arrangements like the solar system throughout the thousands of planetary systems found in our galaxy, the Milky Way

The duo's research was published Wednesday (Sept. 7) in the journal Monthly Notices of the Royal Astronomical Society.

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Robert Lea
Senior Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.