World seen plunging into its star for the first time

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Astronomers spot a planetary ‘suicide’

11 Apr 2025

A few billion years from now, the Sun will begin to burn out and swell to hundreds of times its current size, consuming Earth and the other inner planets in a fiery haze of plasma.

Astrophysicists had originally thought this was the only way for a star to consume its planets, but now, astronomers working with NASA’s JWST spacecraft have uncovered a new way for a planet to meet its end: plunging itself into its host star, as they report this month in The Astrophysical Journal.

“This is a very compelling story they’ve put together,” says Adam Burgasser, an exoplanet researcher at the University of California San Diego who was not involved in the research. “The star wasn’t actually swelling; the planet was falling.”

The star, which lies 12,000 light-years away in our own Milky Way Galaxy, first caught researchers’ attention in 2023 when it flashed brightly. This original observation, captured by the Zwicky Transient Facility on a 1.2-meter telescope at the Palomar Observatory, suggested the star had absorbed a planet during its end-of-life expansion called the red giant stage. It was the first time astronomers had witnessed such an act of celestial infanticide.

When proposing objects to observe with the much bigger JWST, the same researchers knew they had to revisit the crime scene. “If this was the first directly detected planetary engulfment event, what better target is there to point at?” says Ryan Lau, astronomer at the National Science Foundation’s NOIRLab and lead author of the new study.

But, like a plot twist in a Dashiell Hammett crime novel, the new observations scramble the neat original narrative. The star’s luminosity shows it’s too young to have matured to its red giant stage, meaning it couldn’t have puffed up to envelop the planet.

Instead, Lau and colleagues now think the Jupiter-size planet likely orbited the star at about the same distance that Mercury orbits our Sun. Over millions of years, the planet crept closer and closer to the star, with its orbit gradually shrinking until the two orbs suddenly merged. The resulting cataclysm was less an instance of infanticide and more an act of astrophysical suicide. The impact left the star spewing its outer layers of gas, which would eventually chill to a cool dust.

The planet’s long, winding death spiral probably started as the star’s gravitational pull deformed it in the same way the Moon creates the tides in Earth’s oceans, the researchers think.

The constant stretching of such tidal deformation would create friction within the planet that would soak up some of its orbital energy, causing it to edge closer to the star. Eventually, the planet would graze the star’s atmosphere, experience tremendous drag, and plunge into the star even as it disintegrated.

The new analysis is still preliminary, however. “We know we can rule out the initial proposal that the star swelled up, but this is more indirect evidence,” Lau says. So far, the JWST observations have been made in a narrow band of infrared light, he notes.

By tapping into JWST’s full observational bandwidth and looking at longer infrared wavelengths, the team might learn more about those surrounding dust clouds to test the new narrative, Lau says.

Burgasser also wonders how these results will hold up with time. Because intervening dust may block light from the star, it could appear dimmer than it truly is, disguised as a younger version of itself.

More measurements will likely be needed to probe that possibility. If such observations confirm the reported luminosity “that would really seal the deal” for the new explanation, Burgasser says.

He is also curious how often planets die this way. With the Vera C. Rubin Observatory in Chile set to begin observations later this year, astronomers will soon have the highest definition snapshots of the cosmos yet; Burgasser thinks they might find more planets similarly spiraling to their doom. “It may be that this is a fairly common occurrence.”

doi: 10.1126/science.zneqgmu


An artist’s rendering of a planet spiraling into its host star, albeit in far fewer than the millions of orbits requiredNASA; ESA; CSA; R. Crawford/STScI