The star blinked once—just a flash in the sky above Palomar Observatory in 2020. To most, it was another transient burst in the cosmos, one among countless. But to these astronomers, it looked like the moment a planet met its end.
It wasn’t until NASA’s James Webb Space Telescope (JWST) turned its eye to the scene that the story took an unexpected turn. The planet had not been swallowed by a swelling red giant, as once thought. It had spiraled inward, drawn by the star’s own gravity, and plunged to its death.
“The planet eventually started to graze the star’s atmosphere,” said Morgan MacLeod, an astrophysicist at Harvard and MIT. “Then it was a runaway process of falling in faster from that moment.”
A Different Kind of Planetary Death
Until not too long ago, astronomers thought that stars only consumed planets after aging into red giants, ballooning outward as they burned through their fuel. In fact, our own Sun is expected to do just that—billow out in a few billion years and consume Mercury, Venus, and even Earth.
But this event, now known as ZTF SLRN-2020, shows this isn’t always the case.
First detected as a burst of optical light by the Zwicky Transient Facility in 2020, the event seemed to fit the mold. The flash was later confirmed by NASA’s NEOWISE mission in the infrared. At first glance, the star looked like a red giant in the act of planetary engulfment.
That version of events, however, didn’t hold up under the gaze of the James Webb Space Telescope.
“With its high-resolution look in the infrared, we are learning valuable insights about the final fates of planetary systems, possibly including our own,” said Ryan Lau, lead author of the new study and astronomer at NSF’s NOIRLab.
Webb’s observations, conducted using its Mid-Infrared Instrument (MIRI) and Near-Infrared Spectrograph (NIRSpec), revealed the star wasn’t as bright as it should have been if it had swelled into a red giant. It had remained compact. That ruled out the traditional engulfment theory.
Instead, Webb found signs of a slowly decaying orbit. Over millions of years, a Jupiter-sized planet had orbited closer and closer to its star, dragged by gravitational tides and atmospheric friction until it disintegrated.
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Reconstructing a Celestial Crime Scene
The dying planet’s final moments were violent. As it plunged inward, it ripped material from the star’s outer layers. That material cooled into dust, forming a faint ring around the star. Closer in, Webb detected a separate, hot disk of gas that looked more like the birthplace of planets than their graveyard.
“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,” said Colette Salyk, an exoplanet researcher at Vassar College and co-author on the paper.
The observation is the first of its kind: a planetary stripping down caught in the act, followed by a detailed look at the wreckage.
Still, questions remain. Could dust along our line of sight be dimming the star and making it appear younger than it is? Might there be other mechanisms nudging planets to spiral into their stars?
“We know we can rule out the initial proposal that the star swelled up, but this is more indirect evidence,” Lau told Science. “This is truly the precipice of studying these events.”
What This Means for Our Cosmic Neighborhood
Scientists have speculated that stars like ours will one day engulf their inner planets. In fact, the Sun is expected to swallow Mercury and Venus — and possibly Earth — in about five billion years. But direct evidence for such events in other systems has been scarce.
ZTF SLRN-2020 changes that. “It’s the most compelling direct detection of a planetary engulfment event,” the team notes.
The James Webb Space Telescope observed ZTF SLRN-2020 as part of a special “Target of Opportunity” program, designed to catch sudden, unpredictable events. New observatories like the Vera C. Rubin Observatory in Chile and NASA’s upcoming Roman Space Telescope will soon begin wide-field surveys of the sky, hunting for more flashes, more spirals, and more planetary endings.
“It may be that this is a fairly common occurrence,” Adam Burgasser, an exoplanet researcher at the University of California San Diego, who was not involved in the study told Futurism.
One death doesn’t tell the whole story. But with Webb leading the charge, astronomers are beginning to write the next chapter in the life cycles of planets. Not every world dies in fire. Some fall slowly, pulled inward by forces they can’t escape.
This one blinked—and was gone.
The findings were published in the Astrophysical Journal.
