Astronomers using the James Webb Space Telescope appear to have made the first-ever direct observation of a star swallowing a planet. 

Clearly the stellar host was the culprit of this gruesome crime. Acts of "planetary engulfment" occur when a star enters its red giant stage — as our own Sun is fated to do — in a period near the end of its stellar evolution in which it slowly cools and puffs outward, dooming any world it eventually touches.

But the astronomer's new study published in The Astrophysical Journal suggests otherwise. They discovered signs that it was actually the ill-fated planet that charged headlong into its own star, in an act of planetary suicide.

"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 lead author Ryan Lau, an astronomer at the NSF NOIRLab in Arizona, in a statement about the work.

Residing some 12,000 light years away, researchers first spotted signs of the star, ZTF SLRN-2020, engulfing a planet in 2023. The telltale was a bright flash of light that betrayed the presence of dust, likely the remains of a disemboweled quondam world. What's more, early evidence suggested that the star was like our Sun, and was entering into its red giant stage.

It was coming together. By all accounts, they had caught ZTF SLRN-2020 red handed, and decided to get a second look with the James Webb. 

"If this was the first directly detected planetary engulfment event, what better target is there to point at?" Lau told Science.

Using the orbital observatory's Mid-Infrared Instrument, though, they made a surprising discovery. The star was simply not bright enough to be a red giant, blowing the case wide open. If it wasn't a red giant, then it couldn't have puffed outward to swallow anything.

Instead, the team believes that the planet was a Jupiter-sized world that orbited close to the star to begin with, perhaps even closer than Mercury orbits our Sun. Disruptions in the tidal forces between the two bodies led the planet to be nudged inward over millions of years.

"The planet eventually started to graze the star's atmosphere," said coauthor Morgan MacLeod, a Harvard astrophysicist, in the statement. "Then it was a runaway process of falling in faster from that moment."

As it met its face, the planet took a chunk out of its star, too, blasting some of its outer layers into space with the impact. Eventually, the ejecta cooled into a ring of cold dust encircling the star. But the bloodstain pattern doesn't quite add up. In another twist, the researchers also found another circumstellar ring of hot molecular gas even closer to the star, resembling a planet-forming region more than it does the vestiges of a vaporized world.

In any case, there's a lot for the astronomers to chew on. Is this what the crime scene of a planetary engulfment typically looks like? And is this a more common form of demise than the red giant hypothesis?

"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," Lau said in the statement. "We hope this is just the start of our sample."

More on Webb discoveries: Fearless James Webb Telescope Stares Down "City Killer" Asteroid That Had Been Feared to Strike Earth


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