Astronomers recently found exciting evidence of a major collision between two planets in a distant star system. The first hint came when a steady star called Gaia20ehk began to behave unusually. This event is somewhat similar to the ancient impact that created our moon.
Gaia20ehk is about 11,000 light-years away and usually shines steadily, much like our sun. But starting in 2016, it began to show odd dips in brightness. By 2021, the changes became even more chaotic. Anastasios Tzanidakis from the University of Washington shared, “Stars like our sun don’t typically act this way. We knew something was up!”
As the team investigated, they realized the flickering wasn’t due to the star itself but rather large amounts of dust and rock passing in front of it. This debris came from two colliding planets orbiting Gaia20ehk. Tzanidakis noted, “It’s incredible that telescopes captured this impact in real time. Similar collisions are rare, and understanding them can tell us about Earth’s formation.”
Planetary collisions were common when solar systems first formed. Over millions of years, these chaotic events settle into the stability we see today, like our solar system. Interestingly, recent observations indicate that such collisions might happen more often than we realize, but they’re difficult to spot from such vast distances.
James Davenport, another team member, explained how unusual it is to find such events: “Researchers usually focus on fast events, so we’re uncovering discoveries that others might have missed.” The fluctuations in Gaia20ehk’s brightness were unexpected, signaling something new was happening.
Using different telescopes, researchers studied the star in infrared light, revealing even more. While visible light from the star dimmed, the infrared light spiked, suggesting the debris was extremely hot. Tzanidakis explained that this heat likely came from the two planets colliding, creating enough debris to dim the starlight.
Interestingly, this collision resembles the impact that led to the formation of Earth’s moon about 4.5 billion years ago. The debris now orbits Gaia20ehk at a distance similar to that of the Earth-moon system from the sun. Researchers speculate that as this material cools, it might eventually form a moon and a planet system similar to our own, but that could take millions of years.
Understanding how often such collisions happen is essential. Davenport points out, “The frequency of these events is crucial for studying life elsewhere in the universe. Our moon is vital for Earth’s stability, allowing conditions ideal for life.” If we can monitor more collisions, we may get closer to answering important questions about life’s potential on other planets.
This groundbreaking work was published in The Astrophysical Journal Letters on March 11.
