Astronomers have observed an unprecedented sequence of events involving a distant star, Gaia20ehk, marked by regular dimming followed by chaotic fluctuations. Such behavior is unusual for sun-like stars, prompting a deeper investigation into the system’s dynamics. The findings offer a rare glimpse into the violent processes of planet formation and potential collisions, shedding light on the origins of planetary systems – including our own.
Two Planets on a Collision Course
Researchers revisited archival data from multiple optical telescopes and the Wide-field Infrared Survey Explorer (WISE) satellite to analyze observations of the star during the period in question. The data revealed that the system began to brighten in infrared light starting in 2021. “The infrared curve behaved in the opposite way to that of visible light,” explained one of the astronomers. “As the visible light began to flicker and dim, the infrared radiation became brighter.”
This allowed the team to reconstruct the events behind Gaia20ehk’s unusual behavior. It began with two large planetesimals or protoplanets drawing closer and entering increasingly tight orbits. This created the regular dimming of the star detectable in visible light.
Hot Debris Cloud Reveals Impact
The pattern abruptly changed in 2021 when the two planets collided. “This catastrophic collision caused the system to light up brightly in the infrared range,” the researcher reported. The resulting debris formed a massive cloud approximately one astronomical unit from the star, intermittently blocking its light and causing Gaia20ehk to appear to flicker chaotically.
However, infrared observations revealed that this flickering was caused by the debris cloud. “The material is so hot that it glows in the infrared range,” the astronomer explained. This phase is ongoing, but over time, the debris will cool. It could then coalesce into fresh celestial bodies – similar to how the remnants of the Earth-Theia collision formed approximately 4.5 billion years ago.
Similar to the Earth-Theia Collision
“So far, Notice very few observations of planet collisions of any kind – and none that have so many similarities to the collision that once created the Moon,” the researcher stated. “By observing such events elsewhere in the universe, we can also learn a lot about the formation of our own world.” Such observations could reveal how frequently these collisions occur and how many of them create systems like that of Earth and the Moon.
“The Moon is one of the ingredients that make Earth such a habitable place,” explained another researcher. “It shields Earth from some asteroid impacts, creates the tides and weather patterns that drive chemical and biological cycles. The Moon may even play a role in plate tectonics.” Knowing how often such dual systems arise in other planetary systems could therefore aid in the search for extraterrestrial life. (doi: 10.3847/2041-8213/ae3ddc)
Source: University of Washington
March 17, 2026 – Nadja Podbregar
