NASA ‘Autopsy’ Reveals Plot Twist in Case of Planet Killed by Star – ryan

NASA’s James Webb Telescope has been investigating the first-ever case of a star caught swallowing a planet—and, in classic crime thriller style, there has been a plot twist.

Instead of the star swelling in size until it engulfed the planet, as was initially suspected, an ‘autopsy’ revealed instead that the planet’s orbit shrank until it fell to its doom in the star.

The pair lay within our own Milky Way galaxy, some 12,000 light-years from Earth—with the flash of light equivalent to the poor planet’s final scream detected back in 2020.

“Because this is such a novel event, we didn’t quite know what to expect when we decided to point this telescope in its direction,” said paper author and astronomer Ryan Lau, of the National Science Foundation’s NOIRLab in Tucson, Arizona, in a statement.

“With its high-resolution look in the infrared, we are learning valuable insights about the final fates of planetary systems, possibly including our own,” Lau added.

Coming in the form of a blast of visible-spectrum light dubbed “ZTF SLRN-2020,” the eyewitness account of the planet’s death (sorry, I’m still running with this metaphor!) was recorded by the Zwicky Transient Facility at the Palomar Observatory in San Diego, California.

Subsequent investigation using data from NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) revealed that the star brightened in the infrared one year before the optical flash, hinting at the presence of dust.

Based on this analysis, published in 2023, researchers proposed that the star was sun-like, and had been aging and swelling into a red giant as it ran out of hydrogen for fuel.

Webb used a two-pronged approach to investigate this stellar crime scene—bringing to bear both its Mid-Infrared Instrument (MIRI) and Near-Infrared Spectrograph (NIRSpec).

Data from MIRI forced researchers to rethink the case—as the star was not found to be as bright as it would have been, had it actually expanded into a red giant.

Instead, the researchers’ crime scene reconstruction suggests that the planet was once Jupiter-sized, but in an orbit close to the host star—one tighter even than Mercury’s orbit around our sun. Over millions of years, the planet’s orbit shrank until doom befell it.

“The planet eventually started to graze the star’s atmosphere. Then it was a runaway process of falling in faster from that moment,” said paper co-author Morgan MacLeod of the Harvard-Smithsonian Center for Astrophysics.

“The planet, as it was falling in, started to sort of smear around the star,” MacLeod added.

As the planet finished its fiery plunge, it would also have blasted gas away from the outer layers of the star—material that would later condense into cool dust over the next year.

The researchers were surprised, however, when NIRSpec also revealed a hot disk of molecular gas circling closer to the star—one that contained molecules including carbon monoxide. Characterizing this gas could help better study this planet’s demise.

“With such a transformative telescope like Webb, it was hard for me to have any expectations of what we’d find in the immediate surroundings of the star,” said paper co-author and exoplanet researcher Colette Salyk of Vassar College in Poughkeepsie, New York, said in a statement.

“I will say, I could not have expected seeing what has the characteristics of a planet-forming region, even though planets are not forming here, in the aftermath of an engulfment,” Salyk added.

Both the upcoming Vera C. Rubin Observatory in Chile and NASA’s Nancy Grace Roman Space Telescope should be able to spot more cases of planets being swallowed by their stars.

“This is truly the precipice of studying these events. This is the only one we’ve observed in action, and this is the best detection of the aftermath after things have settled back down,” said Lau.

He concluded: “We hope this is just the start of our sample.”

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Reference

Lau, R. M., Jencson, J. E., Salyk, C., De, K., Fox, O. D., Hankins, M. J., Kasliwal, M. M., Keyes, C. D., Macleod, M., Ressler, M. E., & Rose, S. (2025). Revealing a Main-sequence Star that Consumed a Planet with JWST. The Astrophysical Journal, 983(2), 87.