At the end of their main sequence lives, stars similar in mass to our Sun will undergo a period of evolution. This stellar evolution is predicted to affect the populations of the planets around them. Because a star expands during its post-main sequence evolution, astronomers expect that most of the exoplanets discovered so far will be absorbed by the expanding star.
Artist's impression of a Sun-like star engulfing a giant exoplanet. Image credit: Gemini International Observatory/NOIRLab/NSF/AURA/M. Garlick/M. Zamani.
Using data from NASA's Transiting Exoplanet Survey Satellite (TESS), astronomers Edward Bryant and Vincent Van Eylen studied 456,941 stars that have just entered the post-main sequence phase.
They used a computer algorithm to look for repeating dips in brightness that indicate an orbiting planet passing in front of a star, focusing on giant planets with short orbital periods (that is, that took no more than 12 days to orbit their star).
They identified 130 planets and planet candidates, including 33 previously unknown ones, orbiting these stars.
They found that such planets were less likely to occur around stars that had expanded and cooled enough to be classified as red giants (i.e., that were further along in their evolution after the main sequence), suggesting that many of these planets may have already been destroyed.
“This is compelling evidence that when stars deviate from their main sequence, they can rapidly cause planets to spiral into them and be destroyed,” said Dr Bryant, an astronomer at University College London and the University of Warwick.
“This has been the subject of debate and theory for some time, but now we can see the impact of this directly and measure it at the level of a large number of stars.”
“We expected to see this effect, but we were still surprised by how efficiently these stars gobbled up their nearby planets.”
“We think the disruption is due to a gravitational tug-of-war between the planet and star, called tidal interaction.”
“As the star evolves and expands, this interaction becomes stronger.”
“Just as the moon pulls on Earth’s oceans, creating tides, a planet pulls on a star.”
“These interactions slow down the planet and cause its orbit to contract, causing it to spiral inward until it either breaks apart or falls into a star.”
“In a few billion years, our sun will expand and become a red giant,” said Dr Van Eylen, an astronomer at University College London.
“When that happens, will the solar system's planets survive? We're finding that in some cases the planets don't.”
“Earth is certainly safer than the giant planets in our study, which are much closer to their star.”
“But we only looked at the earliest part of the post-main sequence phase, the first one or two million years—stars have much more evolution to go through.”
“Unlike the missing giant planets in our study, Earth itself may survive the red giant phase of the Sun. But life on Earth probably will not.”
teams paper was published on October 15, 2025 in the magazine Monthly Notices of the Royal Astronomical Society.
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Edward M. Bryant and Vincent Van Uylen. 2025. Determining the impact of post-main sequence stellar evolution on the population of a transiting giant planet. MNRAS 544(1):1186-1214; doi: 10.1093/mnras/staf1771
