Astronomers have recorded a rare collision between two planets

The study was published in The Astrophysical Journal Letters.

The unusual star was discovered by University of Washington graduate student Anastasios Tzanidikas when he studied archival telescope data.

The star Gaia20ehk, located about 11,000 light-years from Earth, had been behaving quite normally for a long time. But starting in 2016, its light began to dim periodically.

And by 2021, the star's brightness began to change dramatically and unpredictably.

Details

This seemed strange to astronomers: stars of this type usually shine evenly and steadily.

The scientists suggested that the cause may not be in the star itself, but in a huge cloud of dust and debris that passes in front of it and partially blocks its light.

In their opinion, this cloud could have formed after the collision of two planets.

When planets collide, huge amounts of hot debris and dust are thrown into space. As they heat up, they start to emit infrared light.

This is exactly what astronomers saw: when the visible light of a star waned, the infrared radiation around it increased dramatically.

The researchers suggest that the planets first hit each other several times, gradually coming closer together in orbit.

Such "glancing" collisions could have caused the first small changes in the brightness of the star.

Then a more powerful collision occurred, which threw a huge cloud of dust into space.

Why it matters

Events like this help scientists understand how planets and their satellites form.

It is thought that the Moon may have arisen after the young Earth collided with a large celestial body about 4.5 billion years ago.

Therefore, observing similar processes in other star systems helps to better understand how our planetary system formed.

Now the debris cloud continues to orbit the star at a distance roughly comparable to the distance between the Earth and the Sun.

Over time, this material may cool and reassemble into new celestial bodies - perhaps even a system similar to Earth and the Moon.

Background

Planetary collisions are considered an important step in the formation of planetary systems, but observing them directly is extremely rare.

Future observations will help scientists better understand how common such events are in the universe.

Source

Anastasios Tzanidakis et al, Gaia-GIC-1: An Evolving Catastrophic Planetesimal Collision Candidate, The Astrophysical Journal Letters (2026)