Astronomers using NASA’s James Webb Space Telescope just gave a cosmic mystery a serious plot twist.
The event in question—a sudden brightening from a star about 12,000 light-years away—was initially chalked up to the star swelling into a red giant and engulfing a nearby planet, a typical tale in some star systems.
But not this time. Webb’s perceptive infrared gaze, courtesy of its MIRI and NIRSpec instruments, peered deep into the dusty aftermath with its Mid-Infrared Instrument (MIRI) and Near-Infrared Spectrograph (NIRSpec) and found otherwise. The star, ZTF SLRN-2020, wasn’t puffing up like a balloon—it appeared calm. Which means the planet didn’t get accidentally gobbled up in explosive stellar behavior. Instead, the distant world was doomed by a slow orbital death spiral.
The new research, published today in The Astrophysical Journal, revealed that the unfortunate, roughly-Jupiter-sized planet was orbiting way too close for comfort—closer to its host star than Mercury is to our Sun. Over millions of years, that orbit shrank until the planet skimmed the star’s atmosphere. The planet’s material began to “smear around the star,” according to study co-author Morgan MacLeod, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and MIT, in a Webb Space Telescope release. The planet’s story then ended with a fiery faceplant into the star.
“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 Ryan Lau, lead author of the paper and an astronomer at the National Science Foundation’s NOIRLab, in the same release. “With its high-resolution look in the infrared, we are learning valuable insights about the final fates of planetary systems, possibly including our own.”
When the planet’s material smeared onto ZTF SLRN-2020 it likely caused the dramatic brightening that caught astronomers’ attention. In fact, it’s revising astronomers’ account of the first star seen actively swallowing a planet.
The gnarly observation was part of one of Webb’s Target of Opportunity programs—reserved for sudden cosmic weirdness, like supernovas or, apparently, planetary doom spirals. With next-gen telescopes like the Vera Rubin Observatory and Nancy Grace Roman Space Telescope gearing up, we’re likely to catch a lot more of these macabre stories of planetary ends.