Astronomers have observed traces of planetary collisions.
Massachusetts Institute of Technology (MIT)
The star HD 172555 is about 95 light-years away from Earth. In recent years, astronomers have found traces of high-speed collisions around this star that formed about 23 million years ago.
Astronomers initially found large amounts of silica gas around the young star. The presence of silica gas, also known as vaporized rocks, means that some kind of extreme event has occurred there. Later, the researchers found that there was still a lot of dust around the star, and the particles of this dust were unusually small.
Now scientists from the Massachusetts Institute of Technology, Galway National University in Ireland, the University of Cambridge and other places have published in the journal Nature that they have found a ring of gas around the star, which is mainly composed of carbon monoxide.
The carbon monoxide content in this gas ring is equivalent to about 20% of the carbon monoxide in The atmosphere of Venus. But even more puzzling is the fact that these carbon monoxide are only about 10 astronomical units away from the host star (1 astronomical unit is equivalent to an average of the distance between the Earth and the Sun). In protoplanetary disks, gas and dust are often distributed at distances of tens or even hundreds of astronomical units from the host star. And because carbon monoxide is a gas that breaks down easily under light, it's hard to imagine that it's possible to retain it around stars that have been around stars that have been around for 23 million years to this day.
To explain these doubts, the researchers enumerated a number of possibilities. For example, is there an unknown companion star around this star, or does it change the shape of the protoplanetary disk and make carbon monoxide appear close to the host star? Could it be that shock waves in the nebula caused the rocks to vaporize into silica gas? Is it possible that there have been chain impacts of asteroids and comets there? Wait a minute.
But after putting all the data together, the researchers believe the most likely scenario is that two planet-like objects collided at high speeds at least about 200,000 years ago on the outer edge of the terrestrial planet-forming region of the planetary system. The carbon monoxide rings we observe are scattered from the atmosphere of the colliding planets.
This conclusion is consistent with the predictions of the theory of planet formation. Theoretically, such planetary impacts are a common phenomenon in planetary systems of this age. Even our Moon, Earth's moon, was condensed about 4.5 billion years ago by the debris from the collision of a giant planetary object with the primordial Earth.
reference
Astronomers detect signs of an atmosphere stripped from a planet during giant impact
https://news.mit.edu/2021/astronomers-detect-atmosphere-stripped-planet-giant-impact-1020
Carbon monoxide gas produced by a giant impact in the inner region of a young system
https://www.nature.com/articles/s41586-021-03872-x