What happens when exoplanets collide

The tragic idea of ​​the consequences of a collision of two exoplanets gives scientists an idea of ​​what can happen when the planets collide with each other. A similar event could form our moon.

The two-star system BD +20 307 is located at a distance of more than 300 light-years from Earth, its stars are at least one billion years old. Yet this mature system showed signs of swirling, dusty, non-cold debris, as might be expected from stars of this age. The warmth of the debris confirms that it appeared relatively recently under the influence of two bodies the size of a planet.

Ten years ago, observations of this system by ground-based observatories and the Spitzer space telescope received the first hints of this collision when warm debris was first discovered. Now, the stratospheric observatory of IR astronomy SOFIA has found that the brightness of infrared radiation from debris has increased by more than 10% – this is a sign of an increase in the amount of warm dust.

Results published in the Astrophysical Journal confirm that a collision between rocky exoplanets could have occurred relatively recently. Such collisions can change planetary systems. It is believed that a collision between bodies the size of Mars and the Earth 4.5 billion years ago created the debris that eventually formed the moon.

“The warm dust around BD +20 307 gives an idea of ​​the catastrophic effects between rocky exoplanets,” said Maggie Thompson, a graduate student at the University of California at Santa Cruz, and lead author of the article. “We want to know how this system develops after extreme exposure.”

Planets form when dust particles around a young star stick together and increase over time. Residual debris remains after the formation of the planetary system, often in remote, cold regions, such as the Kuiper belt, located beyond Neptune in our solar system. Astronomers expect to find warm dust around young solar systems. As they evolve, dust particles continue to collide and eventually become large enough to either fly out of the system or become drawn into a star. The warm dust around old stars, such as the Sun and two stars in BD +20 307, should have disappeared long ago. Studying dusty debris around stars not only helps astronomers find out how exoplanet systems are evolving, but it also gives a more complete picture of the history of our own solar system.

“This is a rare opportunity to study the catastrophic collisions that occurred in the later stages of the history of the planetary system,” said Alicia Weinberger of the Carnegie Institute and lead researcher of the project. “SOFIA observations show changes in the dust disk over several years.”

SOFIA infrared surveillance cameras called FORCAST are critical for detecting evidence hidden in cosmic dust. When observed in infrared light, this system is much brighter than expected from some stars. Extra energy comes from dusty debris that cannot be seen at other wavelengths.

There are several mechanisms that can make dust shine brighter – it can absorb more heat from stars or approach stars – but it’s unlikely to happen in just 10 years, which is too lightning fast for cosmic changes. When planets collide, a large amount of dust is generated very quickly. This is consistent with the theory of the collision of two exoplanets. The team analyzes subsequent observations to see if there are further changes in the system.