Astronomers Witness Rare Planetary Collision, Offering Clues on Moon's Formation

The dramatic cosmic crash could provide insights into how Earth and its moon were created.

Mar. 12, 2026 at 4:54pm

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Astronomers have observed a rare and violent collision between two planets near the constellation Puppis, about 11,000 light-years from Earth. The event caused the star Gaia20ehk to flicker chaotically, leading researchers to deduce that massive amounts of hot dust and rock debris were blocking the star's light. They believe this debris was formed by the brutal collision, which could offer clues about the formation of Earth and its moon.

Why it matters

Planetary collisions are extremely rare, and this event bears striking similarities to the impact that is believed to have created the Earth-moon system. By studying this cosmic crash, scientists hope to gain valuable insights into how planetary systems form and evolve, as well as what conditions may be necessary for the development of habitable worlds.

The details

Reviewing telescope observations, astronomer Andy Tzanidakis noticed that the star Gaia20ehk, which is similar to our sun, was acting erratically, with its light output flickering chaotically. Further analysis revealed that the dimming was not caused by the star itself, but by massive amounts of hot dust and rock debris drifting in front of it. The team believes this debris was formed by a collision between two planets, which would also explain the initial dip in brightness as the two bodies spiraled closer together before their catastrophic impact.

  • In 2016, the star Gaia20ehk began experiencing three dips in brightness.
  • Around 2021, the star's light output went 'completely bonkers'.

The players

Andy Tzanidakis

A doctoral candidate in astronomy at the University of Washington who noticed the unusual behavior of the star Gaia20ehk.

James Davenport

A UW assistant research professor of astronomy and senior author on the study.

Gaia20ehk

A 'main sequence' star similar to our sun, located about 11,000 light-years from Earth, that began exhibiting erratic behavior.

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What they’re saying

“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. 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?'”

— Andy Tzanidakis, Doctoral candidate in astronomy, University of Washington (The Astrophysical Journal Letters)

“How rare is the event that created the Earth and the moon? That question is fundamental to astrobiology. It seems like the moon is one of the magical ingredients that make the Earth a good place for life. It can help shield Earth from some asteroids, produce ocean tides and weather that allow chemistry and biology to mix globally, and even play a role in driving tectonic plate activity.”

— James Davenport, UW assistant research professor of astronomy (The Astrophysical Journal Letters)

What’s next

The researchers plan to continue studying the Gaia20ehk system to better understand the timeline and details of the planetary collision, as well as its potential implications for the formation of Earth and its moon.

The takeaway

This rare cosmic event provides a unique opportunity to observe a planetary collision similar to the one that is believed to have created the Earth-moon system. By studying the debris and dynamics of this crash, scientists hope to gain valuable insights into the conditions necessary for the formation of habitable worlds.