At the end of their main sequence lifetimes, stars of mass similar to our Sun will experience a period of evolution. This stellar evolution is predicted to influence the population of the planets surrounding them. As the star expands during its post-main sequence evolution, astronomers expect that many of the exoplanets discovered so far will be swallowed up by the expanding star.
Artist’s impression of a Sun-like star engulfing a giant exoplanet. Image credit: International Gemini 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 observed 456,941 stars that had just entered the post-main sequence phase.
They used a computer algorithm to look for repeated dips in brightness that indicate an orbiting planet is passing in front of the star, focusing on giant planets with short orbital periods (that is, those that took no more than 12 days to orbit their star).
They identified 130 planets and candidate planets, including 33 previously unknown, in close orbit around these stars.
They found that such planets were less likely to occur around stars that were sufficiently expanded and cooled to be classified as red giants (i.e., that were further along in their post-main-sequence evolution), suggesting that many of these planets may have already been destroyed.
“This is strong evidence that as stars evolve out of their main sequence, they can quickly cause planets to spiral and destroy themselves,” 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 directly and measure it at the level of a large population of stars.”
“We expected to see this effect, but we were still surprised by how efficiently these stars seemed to gobble up their nearby planets.”
“We think the destruction occurs because of the gravitational tug-of-war between the planet and the star, called a tidal interaction.”
“As the star evolves and expands, this interaction becomes stronger.”
“Just as the Moon pulls on Earth’s oceans to create the tides, the planet pulls on the star.”
“These interactions slow the planet down and cause its orbit to shrink, causing it to spiral inward until it breaks up or falls into the star.”
“In a few billion years, our own Sun will expand and become a red giant,” said Dr Van Eylen, an astronomer at University College London.
“When this happens, will the planets in the solar system survive? We see that in some cases, this is not the case.”
“Earth is certainly safer than the giant planets in our study, which are much closer to their star.”
“But we only looked at the first part of the post-main sequence phase, the first one or two million years – the stars still have a long way to go.”
“Unlike the giant planets missing from our study, Earth itself could survive the Sun’s red giant phase. But life on Earth probably would not.”
The team’s article was published on October 15, 2025 in the Monthly Notices of the Royal Astronomical Society.
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Edward M. Bryant and Vincent Van Eylen. 2025. Determining the impact of post-main sequence stellar evolution on the population of transiting giant planets. MRNRA 544 (1): 1186-1214; doi: 10.1093/mnras/staf1771
