2023-07-10 09:01:36
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The planet Halla (black small celestial body) orbits the giant star Baekdu far too close to survive. Nevertheless, he still exists. (Artist’s rendering) © WM Keck Observatory/Adam Makarenko
Stars bloating and eating their planets is not new. However, researchers are surprised that a planet cannot be swallowed up.
Hawaii – Stars in the Milky Way are eating up the planetsthat orbit them. In the distant future, Earth faces the same fate, as the Sun will inflate in about five billion years after running out of hydrogen. Then it will become so large that it will swallow up at least the planets Mercury, Venus and Earth. However, a team of researchers led by University of Hawaii astronomer Marc Hon has discovered a planet that appears to have escaped that fate. The results of this study were in the renowned journal Nature published.
The planet Halla (8 UMi b) orbits the star Baekdu (8 UMi) at a distance of about 69 million kilometers, which is about half the distance between Earth and the Sun (150 million kilometers). The research team noted that the star is already burning helium at its core, indicating that it has ballooned into a red giant star in the past. The question of why the planet Halla escaped this enormous change in size occupied the research team, who then tried to find an explanation.
Exoplanet Halla is apparently an ‘extraordinary survivor’
Marc Hon, the lead author of the study, explains in a communication: “The devour of a planet has catastrophic consequences, either for the planet or for the star itself – or for both.” He continues: “The fact that Halla has managed to survive in close proximity to a giant star that would otherwise would have devoured makes the planet an exceptional survivor.”
Baekdu (8 Ursa Minoris)Roter RiesensternKleiner Bär1,8 Sonnenmassen9,9 Sonnenradien4574,25 Grad CelsiusHalla (8 Ursa Minoris b)
Halla is an exoplanet classified as “Hot Jupiter”. This planet has at least the mass of Jupiter, but its surface temperature is significantly higher than that of Jupiter (-108 degrees Celsius). The common assumption in research is that hot Jupiters once existed in distant orbits around their stars and then migrated inward. However, the researchers consider this to be unlikely in the case of Halla.
Exoplanet Halla: Has its star merged with another star?
The research team’s guess is that the star Baekdu may have once been part of a binary star system. If the two stars had merged, it could have prevented one of them from expanding to swallow the planet. Daniel Huber, co-author of the study, explains in one articles on the platform The Conversation: “If a star had become a red giant on its own, it would have engulfed Halla – but if it had merged with a companion star, it would have gone straight into the helium combustion phase without growing large enough to reach the planet.”
An alternative explanation for the persistence of the planet Halla could be that the planet formed only recently. This theory suggests that the violent collision of two stars could have created a cloud of gas and dust within which the planet Halla formed. Daniel Huber adds: “In other words, the planet Halla could be a recently born ‘second generation’ planet.”
Exoplanet Halla is ‘some kind of forbidden planet’
Study leader Hon adds: “Most stars are in binary systems, but we don’t yet fully understand how planets can form around them. Therefore, it is plausible that there could be more planets around advanced stars thanks to the interactions between the binary star systems.”
Regardless of how the planet Halla has managed to survive, one thing is certain: it is like Marc Hon to it the New York Times puts it, “a sort of forbidden planet.” Hon further explains, “The star itself may have a very unusual history that has allowed the planet to survive at such a close range from an otherwise rather inhospitable host star.”
Machine assistance was used for this editorial-written article. The article was carefully checked by editor Tanja Banner before publication.
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