A planet’s fiery end has taken an unexpected turn, thanks to fresh observations from NASA’s James Webb Space Telescope (JWST). Once believed to have been swallowed by an expanding star, the doomed world now appears to have plunged into its host star on its own — a death spiral millions of years in the making.
This dramatic update revises what astronomers initially thought was the first-ever sighting of a star engulfing a planet. Rather than being consumed by a swelling red giant, the planet gradually spiraled inward, grazing the star’s atmosphere before triggering a catastrophic chain of events.
Star’s Deadly Embrace Reconsidered
Back in May 2020, astronomers caught sight of an unprecedented event: a star seemingly engulfing a planet. It was dubbed ZTF SLRN-2020, named after the Zwicky Transient Facility that spotted a burst of optical light from a star about 12,000 light-years away in the constellation Aquila. The original theory was straightforward — as the star aged and expanded into a red giant, it ballooned outward and swallowed a tightly orbiting planet, likely a gas giant several times the mass of Jupiter. But new observations by JWST have upended that narrative.
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Planet Came to the Star
Rather than the star expanding and reaching the planet, researchers now believe the planet was the one spiraling inward over millions of years. Gravitational interactions and tidal forces caused its orbit to erode until it ultimately plunged into the star.
“It starts grazing through the atmosphere of the star. Then the headwind from the stellar atmosphere takes over, and the planet falls increasingly rapidly,” explained Morgan MacLeod of the Harvard-Smithsonian Center for Astrophysics. As it sank, the planet lost its outer layers and triggered violent ejections of stellar gas — the dramatic final act recorded in 2020.
Webb’s Instruments Reconstruct the Scene
JWST’s two infrared instruments, MIRI (Mid-Infrared Instrument) and NIRSpec (Near-Infrared Spectrograph), provided the forensic evidence. MIRI revealed that the host star lacked the brightness expected from a red giant, contradicting the initial swelling theory. This was key in proving the star hadn’t expanded significantly, and the planet had instead spiraled inward.
JWST’s NIRSpec found something equally compelling: a hot disk of molecular gas — including carbon monoxide — close to the star, and a surrounding halo of cold dust likely formed from the expelled outer layers. This indicated a more complex and prolonged end than previously assumed.
Aftermath and Implications
“This is truly the precipice of studying these events,” said lead author Ryan Lau of NSF’s NOIRLab. “It’s the only one we’ve observed in action, and the best detection of the aftermath.” The event was captured under Webb’s Guaranteed Time Observation program 1240, which aims to investigate short-lived cosmic outbursts.
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This discovery not only rewrites the final chapter of ZTF SLRN-2020, but also offers a cautionary glimpse into our own solar system’s future. While none of our planets are currently close enough to be at risk, the sun is expected to become a red giant in about 5 billion years — likely engulfing Mercury and Venus, and possibly Earth. With upcoming observatories like the Vera C. Rubin Observatory and NASA’s Nancy Grace Roman Space Telescope, astronomers hope to catch more of these rare death dives in real-time.