The number of exoplanets, planets orbiting distant stars, significantly exceeds the number of stars themselves, black holes, galaxies and other space objects of larger scales. And if astronomers manage to find traces of collisions of very rare types of stars and black holes, then collisions of exoplanets, leaving behind trails of dusty ruins, should be even more common in the universe. And just recently, astronomers managed to witness such a cataclysm that occurred in the relatively recent past.
The scene in which the space “accident” occurred is a system called BD +20 307, located 200 light-years from Earth. There are two stars in this system, about one billion years old, and the evidence of an exoplanet collision is a cloud of debris that has not even had time to cool down.
Clouds of debris in stellar systems is a rather ordinary phenomenon, even in the solar system there is something similar – the Kuiper belt. But these things are of a completely different nature, they, as astronomers believe, are the remains of material that was not fully used up at the time of the formation of the planets of the system. But the asteroid belt of the Solar System may well be the result of a collision of two planets, but in 4.5 billion years in space all this has already managed to cool to a very low temperature.
Given the presence of two stars in the BD +20 307 system and the age of these stars, any accumulations of matter remaining after the formation of the system should have had time to cool by now. However, the data obtained 10 years ago using the Spitzer Space Telescope infrared telescope showed that the dust clouds in this system are still quite warm. This, in turn, indicates a large-scale collision of exoplanets that occurred relatively recently in the system.
The fact of the collision of the planets received additional evidence after analyzing the data collected by the flying observatory SOFIA (Stratospheric Observatory for Infrared Astronomy). An analysis of the data showed that the temperature of the clouds in reality is 10% higher than the results of previous observations.
However, the presence of warm dust clouds in the BD +20 307 system can be explained by other factors. It is likely that these clouds drift along a complex path, approaching the stars and absorbing the energy emitted by them in the form of ordinary, infrared and ultraviolet light. But this scenario is very unlikely, because such a process could not lead to 10 percent heating over a 10-year period of time, which is less than flickering with an eye on the cosmic time scale.
Therefore, the collision of the planets is the most likely explanation for what happened in the BD +20 307 system. The increased amount of dust and debris in the clouds of this system also speaks in favor of this. And astronomers plan to make further periodic observations of the BD +20 307 system, which will allow them not to miss any sharp changes in this area of outer space.