2 planets collide 11,000 light-years from Earth in rare sight

Two planets crashed into one another in a violent, chaotic collision that astronomers recently witnessed 11,000 light-years away from Earth.

The rare cosmic event is not one scientists get to see every day.

But thanks to a bit of serendipity, a researcher at the University of Washington looking through old telescope data happened upon the bread crumbs that would lead him to the stunning discovery. A distant star located at a distance equal to nearly halfway from Earth to the galactic center of the Milky Way was displaying short dips in brightness before apparent chaos erupted.

“Right around 2021, it went completely bonkers,” study lead author Anastasios Tzanidakis, a researcher at the University of Washington, said in a statement. “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?’ ”

The phenomenon, which researchers claimed had never before been observed, led them to conclude that what they were seeing was evidence of a planetary collision, according to a study published March 11 in the Astrophysical Journal Letters.

Here’s everything to know about the wild discovery.

Astronomers discover evidence of 2 planets colliding 11,000 light-years away

By reviewing old telescope data from 2020, Tzanidakis discovered that an otherwise unremarkable star had begun acting strangely.

Beginning in about 2016, the star Gaia20ehk in the constellation Puppis in the southern sky underwent three unusual dips in brightness. Investigating further, Tzanidakis concluded that the strange flickering had nothing to do with the star itself.

Instead, “huge quantities of rocks and dust” were passing in front of the distant star while orbiting in the same planetary system – intermittently dimming the star’s light that managed to reach Earth, according to the press release. Even further investigation revealed something remarkable: the source of that debris was likely remnants of two planets crashing into one another.

To reach the conclusion, Tzanidakis and study co-author James Davenport, an astronomer at the University of Washington, used telescopes to examine the fluctuation in not just visible light, but infrared light. That’s how the researchers noticed that the invisible infrared light spiked anytime the visible lights flickered, suggesting the material blocking the star was incredibly hot.

“That could be caused by the two planets spiraling closer and closer to each other,” Tzanidakis said. “At first, they had a series of grazing impacts, which wouldn’t produce a lot of infrared energy. Then, they had their big catastrophic collision.”

How do planets form?

Planetary formation is preceded first by the birth of stars, which form when an accumulation of gas and dust collapses because of gravity. Scientists think that generally what follows is the formation of planets, which emerge from the giant, doughnut-shaped disk of gas and dust that circles young stars, known as protoplanetary discs.

Gravity and other forces cause material like dust, gas, ice or rocky debris to collide in a process that, if gentle enough, binds the matter together so that forming planets – known as planetesimals – can grow like rolling snowballs.

These planetesimals begin to orbit their new star, pushing material out of their way as the star devours nearby gas and pushes more distant material farther away to form additional worlds within the solar system, NASA explains.

As common as a process as this likely is throughout the universe, it’s rare for scientists to have a front row seat to such a collision, according to the researchers.

Crash between planets could shed light on Earth, moon

What’s more, Tzanidakis and Davenport’s research suggests the collision resembles the one that created Earth and its singular moon about four and half billion years ago. That’s because the dust cloud orbiting the distant star is about the same distance from the sun to Earth, which would allow the material to eventually cool down and solidify into something resembling our planet and our only natural satellite.

Even more tantalizing, the researchers posit that the discovery could be the tip of the iceberg if more evidence of planetary collisions are out there – and some could be worlds that are habitable.

“There are only a few other planetary collisions of any kind on record, and none that bear so many similarities to the impact that created the Earth and moon,” Tzanidakis said in the statement. “If we can observe more moments like this elsewhere in the galaxy, it will teach us lots about the formation of our world.”