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What happens when exoplanets crash into each other?

More than 300 light-years from Earth, there’s a double star system where evidence exists that two exoplanets, or planets outside of our solar system, recently collided.

Astronomers used NASA’s Stratospheric Observatory for Infrared Astronomy to spot a warm dust and debris trail within the system, according to a release by NASA. SOFIA is a flying observatory consisting of a Boeing 747 modified to carry a telescope.

The binary star system, where the stars are around a billion years old, is known as BD + 20 307. It was observed with NASA’s Spitzer Space Telescope a decade ago, Those observations hinted at the presence of warm debris. In a system with stars this old, astronomers expected the debris would be cold.

But the follow-up observations by SOFIA suggest that two rocky exoplanets collided. SOFIA was able to see the warm glow of the dust in infrared that other wavelengths of light wouldn’t reveal. A study of the collision published this week in The Astrophysical Journal.

“The warm dust around BD +20 307 gives us a glimpse into what catastrophic impacts between rocky exoplanets might be like,” said Maggie Thompson, lead study author and graduate student at the University of California, Santa Cruz. “We want to know how this system subsequently evolves after the extreme impact.”

Some scientists think that Earth’s moon formed after Earth collided with a planetary body the size of Mars 4.5 billion years ago. These kinds of collisions can restructure a solar system.

The current understanding for planet formation follows a specific order. Stars form from clouds of collapsing gas and dust. Then, a protoplanetary disk of leftover gas and dust surrounds the star. Planets form from this disk, using the leftover gas and dust that created the star to pull together solid material for planets.

Any dust leftover from this process is either pulled back into the star or ejected from the system. So the presence of the warm dust around these stars was a strong indicator of an enormous collision between planets.

“This is a rare opportunity to study catastrophic collisions occurring late in a planetary system’s history,” said Alycia Weinberger, lead investigator and staff scientist at the Carnegie Institution for Science’s Department of Terrestrial Magnetism. “The SOFIA observations show changes in the dusty disk on a timescale of only a few years.”

CNN