Big stars may commit Grand Theft Planet

Young stars more than twice the mass of the Sun generate so much radiation that it is very difficult for planets to collect dust and gas. However, a handful of exoplanets that are more massive than Jupiter and in orbits farther than Pluto have been discovered around these O and B stars. New Research published in Monthly Notices of the Royal Astronomical Society It indicates that these planets may have originally formed around smaller nearby stars, and were later stolen by the more massive planets.

“Basically, this is planetary theft,” co-author Emma Davern Powell said in statement. Daffern-Powell is an astronomer at the University of Sheffield in the United Kingdom. We used computer simulations to show theft or appropriation [planets] It occurs on average once in the first 10 million years of the evolution of the star-forming region.”

planet thieves

Astronomers posit that stars like our sun build planets from a swirling disk of dust and gas. (many notes supports this theory.) The gravitational instability in the disk causes small clumps of planetary material to collapse inward and collect more material. However, intense stellar radiation such as the type produced by O and B stars (at least twice but sometimes more than 20 or 50 times the mass of the Sun) can disrupt accumulation through a process called photoevaporation.

“It’s hard to find planets About stars O and B, which are bright stars,” the lead author said Richard Parker, an astrophysicist at the University of Sheffield in the United Kingdom. “There is nothing at first glance that stops O [and] stars b planet formation… However, extreme ultraviolet and ultraviolet rays are strong enough to evaporate gas from the protoplanetary disks, and if there is no gas, it is impossible to form planets with the mass of Jupiter in the disk. “

This artist’s impression shows a gas giant planet in distant orbit around a massive blue star in a mass similar to the Scorpius-Centaurus association. attributed to him: Mark Garlickpublic domain

This does not mean that massive stars do not host exoplanets. a recent study From a young star cluster, the Scorpius-Centaurus Society (Sco-Cen)which contains dozens of a And the B Stars, confirmed the presence of at least two exoplanets and one candidate planet larger than Jupiter around these inhospitable stars.

In an effort to explain these planets, Parker and Davern Powell explored the possibility of planets forming elsewhere and later making their way into orbits around massive stars. They ran computer simulations that modeled a group of young stars, some of which were given simulations of exoplanets, and tracked the fate of these exoplanets for 10 million years.

Simulations showed that when a less massive star and an exoplanet approached a more massive star, the massive star uprooted the planet from its orbit. Either the more massive star would immediately steal the planet itself, or the planet would be left floating freely within the cluster; This planet may later be captured by a different massive star. After repeating the simulation several times, the researchers found that, on average, O and B stars steal or capture about one exoplanet every 10 million years from a low-mass star.

Formation of planetary systems from the outside

Simulations revealed that the captured planets could have orbits ranging in size from 4 times the distance between Earth and the Sun (astronomical units, or AU) to 10,000 astronomical units. The stolen planets were likely to orbit 200 AU. Two of the three exoplanets discovered so far in Sco-Cen orbit have detected more than 200 AU from their stars, suggesting that they were captured rather than stolen from the stars on which they were born. (Sco-Cen also contains a file Large set of free float or rogue planets, which may eventually be captured).

“Instead of looking inside a planetary system, we should sometimes think about what happened in the outside. “

He commented, “Their scenario seems perfectly plausible.” Sean Raymond, an astronomer at the Astrophysics laboratory de Bordeaux in France and was not involved in the study. “It’s new, interesting and carefully simulated. I just think it’s really cool.”

The researchers acknowledged that due to computational limitations, their simulations did not include Binary stars, which is very common in young constellations. With stronger gravity, two stars are more likely to capture or steal a planet than one star, Parker explained, so it is likely that more planets around O and B stars will be stolen or captured than this simulation suggests. The team plans to include binary stars in future simulations.

“I think the role of star clusters in planetary systems is really understated,” Raymond said. “This work shows that instead of looking inside a planetary system, we should sometimes think about what happened in the outside. “

—Kimberly MS Cartier (Tweet embed), crew writer

the quote: Cartier, KMS (2022), Massive Stars May Commit a Great Robbery of Our Planet, Eos, 103, https://doi.org/10.1029/2022EO220462. Posted on September 23, 2022.
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