The discovery, co-authored by Dr Rosemary Mardling, is rare because “BEBOP-1c” is one of two planets in a single system orbiting two suns, a phenomenon known as a circumbinary system.
“We are aware of 12 circumbinary systems so far, and this is only the second one that has more than one planet,” said Dr David Martin, a co-author of the paper who is a former student of Dr Mardling’s.
The first planet in the system, TOI-1338b, was discovered in 2020 as it passed in front of the larger of the two stars several times, and the team tried to measure its mass by installing cutting-edge equipment on two telescopes in Chile.
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While they were not successful, they instead found a second planet, BEBOP-1c.
“The orbital period of BEBOP-1c is 215 days, and its mass is 65 times that of Earth, which is about five times less than Jupiter’s mass,” said Monash University.
“This was a challenging system to confirm because telescopes in Chile were closed for six months because of the COVID pandemic during a crucial part of the planet’s journey around its two parent stars. This particular section of the orbit could only be observed again last year, enabling the research team to confirm their discovery.
“While only two planets are currently known to orbit the TOI-1338/BEBOP-1 binary system, future observations by the team may reveal more. Even though they are rare, circumbinary planets are important for learning about how planets form.”
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Dr Mardling said that with an orbital period around 6.5 times that of the binary, BEBOP-1c is almost as close as it can be to the two stars. Any closer, and it would be kicked out of the system by the binary’s intense gravitational field.
“And with a period only twice that of BEBOP-1c, TOI-1338b is also perilously close to being thrown out of the nest,” she said.
“This tells us much about the conditions in which such planets form.”
The new planet was named BEBOP-1c because the project that discovered it is called BEBOP, or Binaries Escorted By Orbiting Planets. The system is known as BEBOP-1 or TOI-1338.
“Two stars act like a giant paddle, stirring up and stopping planets from forming anywhere but in quiet places far from the binary,” said Monash University.
“But the TOI-1338/BEBOP-1 planets are close to their binary, as are all known circumbinary planets. In fact, the disc pushes them inwards as they form, stopping them just before they are evicted from the system.
“While the radial velocity method has allowed the research team to measure the mass of BEBOP-1c, it will now try to measure its size using the transit method.”
Adam Thorn
Adam is a journalist who has worked for more than 40 prestigious media brands in the UK and Australia. Since 2005, his varied career has included stints as a reporter, copy editor, feature writer and editor for publications as diverse as Fleet Street newspaper The Sunday Times, fashion bible Jones, media and marketing website Mumbrella as well as lifestyle magazines such as GQ, Woman’s Weekly, Men’s Health and Loaded. He joined Momentum Media in early 2020 and currently writes for Australian Aviation and World of Aviation.
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