When the Sun finally swells into a red giant billions of years from now, it may not be kind to its planets. New research using NASA’s Transiting Exoplanet Survey Satellite (TESS) suggests that stars in this aging phase are far more destructive than once believed — swallowing nearby worlds with ruthless efficiency. The findings raise questions about what could happen to Earth when our own star meets this fiery fate.
How Did Scientists Discover These Planetary Casualties?
Astronomers used TESS, a telescope that tracks tiny dips in starlight caused by orbiting planets, to search through nearly half a million stars. From this vast dataset, a team identified about 15,000 possible planetary signals, eventually narrowing them to around 130 planets orbiting stars just beginning their red giant stage. Among these, 33 were newly identified candidates, marking a rare look at systems on the edge of stellar transformation.
Their analysis revealed a striking pattern — close-orbiting planets around red giants are incredibly scarce. This means many planets likely perish as their stars begin to expand. “As stars evolve off their main sequence, they can quickly cause planets to spiral into them and be destroyed,” said Edward Bryant of the University of Warwick, a member of the research team. “We expected this, but we were surprised by how efficient the process is.”
Why Do Red Giants Destroy Their Planets?
When stars like the Sun run out of hydrogen in their cores, fusion slows and the outer layers balloon outward. The star can swell up to 1,000 times its original size, marking the start of the red giant phase. For planets that orbit close by, this expansion can be fatal.
Bryant explained that destruction often results from a gravitational tug-of-war between the star and its planet, known as tidal interaction. “As the star expands, the interaction grows stronger,” he said. “Just like the Moon pulls on Earth’s oceans, planets pull on stars. This slows the planets down, forcing them inward until they break apart or fall in.”
The researchers found that stars which had already started expanding had only a 0.11% chance of hosting a planet — about 3% lower than younger, main-sequence stars. The likelihood of red giants hosting large planets, such as Jupiter or Saturn, also declined as the stars aged.
What Does This Mean for Earth’s Future?
So, could the same fate await our planet when the Sun becomes a red giant? Possibly — but not right away. “Earth is certainly safer than the giant planets in our study, which orbit much closer to their stars,” said Vincent Van Eylen of University College London, a co-author of the study. “Earth might survive the Sun’s red giant phase, but life on it probably would not.”
The researchers now plan to collect more data to understand why some planets survive while others perish. “Once we know their masses, we can understand exactly what causes these planets to spiral in and be destroyed,” Bryant added.
The study, published in the October edition of the Monthly Notices of the Royal Astronomical Society, provides one of the clearest signs yet that red giants can rapidly consume their planets — offering a haunting preview of what might one day happen in our own solar system.