'Completely bonkers': Astronomers spot a planetary collision 11,000 light-years away
Astronomers at the University of Washington have observed something rare: a planetary collision as it happens. The star Gaia20ehk, located roughly 11,000 light-years from Earth near the constellation Pupis, started behaving strangely in 2021.
Astronomers at the University of Washington have observed something rare: a planetary collision as it happens.
The star Gaia20ehk, located roughly 11,000 light-years from Earth near the constellation Pupis, started behaving strangely in 2021. Its brightness fluctuated unpredictably. "Completely bonkers," said Anastasios (Andy) Tzanidakis, a UW doctoral candidate and lead author of the study, in an interview with UW News.
The cause, according to research published March 11, 2026 in the Astrophysical Journal Letters, is debris from a collision between two planets. The evidence came from infrared data showing a pattern opposite to what was visible in optical light — a signature of a expanding dust cloud, not intrinsic stellar variation.
The dust cloud now orbits the star at approximately one astronomical unit (the Earth-sun distance), with a temperature around 900 Kelvin and a mass of roughly 4×10²⁰ kilograms. That puts it in the same ballpark as the debris field astronomers believe surrounded the early Earth after the giant impact that formed the moon.
Whether this system will eventually coalesce into a moon-forming configuration remains uncertain. "It could happen," the researchers noted, but the process would take tens of millions of years — if it happens at all.
The discovery is significant because planetary collisions are thought to be common in young solar systems, but actually catching one in progress is exceedingly rare. Most known examples involve indirect evidence. This one offered astronomers a front-row seat.
James Davenport, UW assistant professor and senior author on the paper, said the find underscores how dynamic planetary systems can be — even over human observational timescales.
This article synthesizes reporting from UW News with verification against the original Astrophysical Journal Letters paper. The 'completely bonkers' quote and specific dust measurements come directly from the university press release and paper.
