When Planets Collide: Evidence of a Massive Exoplanetary Collision Found

The dust cloud orbiting BD +20°307 contains about 1 million times more dust than is orbiting the Sun. Furthermore, the dust is made up of extremely tiny particles, and its temperature is over 100 K, which is surprisingly high. 

In a solar system far, far away, two exoplanets crashed into each other. Although we didn’t see the massive collision take place, studying the solar system has revealed tell-tale signs of the cosmic collision. 

Astronomical observations of a double star system located around 300 light-years from Earth has revealed evidence of a relatively recent extreme collision between two rocky exoplanets.

The star system known as BD +20 307 is at least 2 billion years old. And instead of showing debris of dust that are cold as expected in a solar system of that age, astronomers have found debris that are extremely hot, suggesting that a massive cosmic collision took place between two rocky bodies not long ago.

The first signs of the cosmic collision in BD +20 307 were discovered a decade ago by ground observations and NASA’s Spitzer Space Telescope.

Now, astronomers using the Stratospheric Observatory for Infrared Astronomy, SOFIA, revealed the infrared brightness from the debris has increased by more than ten percent, a sign that suggests there’s even more warm dust now.

It’s as if Earth and Venus collided,” said Prof. Benjamin Zuckerman, UCLA professor of physics and astronomy.

“Astronomers have never seen anything like this before. Apparently, major catastrophic collisions can take place in a fully mature planetary system.”

The new data obtained by astronomers has been published in the Astrophysical Journal and directly supports the idea that a catastrophic collision took place relatively recently between two rocky worlds. Astronomers argue that such cosmic collisions have the ability to completely alter a planetary system.

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In fact, scientists maintain that some 4.5 billion years ago, a Mars-sized body and the early Earth collided and its debris eventually formed Earth’s Moon.

“The warm dust around BD +20 307 gives us a glimpse into what catastrophic impacts between rocky exoplanets might be like,” explained Maggie Thompson, a graduate student at the University of California, Santa Cruz, and the lead author on the paper.

“We want to know how this system subsequently evolves after the extreme impact.”

Planets in the universe are believed to form when dust particles around young stars unite and grow larger over time.

The leftover remains tend to prevail after a planetary system is formed, often in distant and cold regions such as the Kuiper Belt, an area of space within our solar system located beyond Neptune.

Astronomers expect to find warm dust around young solar systems. As they evolve, the dust particles continue to collide and eventually become small enough to be ejected from a system or pushed towards the star where the material is devoured by the star.

This is why warm dust around older stars, such as our Sun and at BD +20 307, should have disappeared a long time ago.

Studying the dusty remains around the stars not only helps astronomers learn how exoplanet systems evolve but also produces a more comprehensive picture of the history of our own solar system and solar system formation.

“This is a rare opportunity to study catastrophic collisions occurring late in a planetary system’s history,” explained Alycia Weinberger lead investigator on the project.

“The SOFIA observations show changes in the dusty disk on a timescale of only a few years.”