Astronomers have observed a rare cosmic event: the collision of two planets orbiting a star approximately 11,000 light-years from Earth. The dramatic event was detected near the star Gaia20ehk, located in the constellation Puppis. This discovery offers a unique glimpse into the violent processes that can shape planetary systems and potentially contribute to the formation of fresh worlds.
The initial observation came from University of Washington doctoral candidate Anastasios Tzanidakis, who was reviewing telescope data from 2020 when he noticed unusual light patterns emanating from the star.
Gaia20ehk is a stable, sun-like star, typically expected to emit a consistent level of brightness. However, data revealed unusual fluctuations in its light output over several years.
Caption: Astronomers have observed a rare cosmic event: the collision of two planets approximately 11,000 light-years from Earth. The event was detected around the star Gaia20ehk, near the constellation Puppis.
“The star’s light output was nice and flat, but starting in 2016 it had these three dips in brightness. And then, right around 2021, it went completely bonkers,” said Tzanidakis.
He explained that the situation became even more peculiar in subsequent years, with drastic changes in brightness levels prompting researchers to investigate the cause of the phenomenon.
“I can’t emphasize enough that stars like our sun don’t do that. So when we saw this one, we were like ‘Hello, what’s going on here?’” Tzanidakis stated.
Further analysis revealed that the source of the disturbance wasn’t the star itself. Instead, the light reaching Earth was being obscured by debris orbiting the star.
This material, believed to be rocks and dust, is thought to originate from a massive collision between two planets. As the debris passed in front of the star, it caused the light reaching Earth to dim.
“It’s incredible that various telescopes caught this impact in real time,” Tzanidakis said.
He noted that observed planetary collisions are rare, and events resembling the impact that may have created Earth and the Moon are almost never directly detected.
The team’s research was published on March 11 in The Astrophysical Journal Letters. The article is titled “Gaia-GIC-1: An Evolving Catastrophic Planetesimal Collision Candidate”.
Another researcher from the University of Washington, James Davenport, suggested the team review data from infrared observations. This approach yielded surprising new findings.
“The infrared light curve was completely opposite to the visible light,” Tzanidakis explained.
He clarified that as the visible light began to dim, the infrared light sharply increased, indicating that the material obscuring the star was extremely hot.
