Andy Tzanidakis
Depiction, by lead author Andy Tzanidakis, of the planetary collision suspected to have occurred around the star Gaia20ehk in 2021.
The discovery documents, for the first time, the collision between two exoplanets in real time, by analyzing the violent fluctuations in the light of their host star — a phenomenon that astronomers have hoped to observe for years.
Or astronomer Anastasios Tzanidakis was reviewing archival telescope data from 2020 when he came across a seemingly unremarkable star that was behaving in an extraordinarily strange way.
The object in question, cataloged as Subject: 20is located about 11 thousand light years from Earth, near the constellation Puppis.
It was a stable starvery similar to our Sun, which would normally imply a constant and predictable light emission. However, records indicated that the star had started to flicker erratically.
In one from the University of Washington, Tzanidakis explains that the star’s light curve remained flat and unchanged until, starting in 2016, three significant drops in its brightness.
The situation became chaotic around 2021when the star, in his words, “went completely crazy”.
The researcher highlights the exceptional nature of the eventremembering that stars like the Sun they just don’t behave this waywhich led the team to wonder what was going on after all.
The origin of this flickering, as revealed after a thorough analysis, had no nothing to do with the star itself. The cause lay in enormous amounts of rocks and dust that seemed to appear out of nowhere and they orbited within the system, passing in front of the distant star and partially and irregularly attenuating the light that reached our instruments.
The most likely source of such a vast amount of debris turned out to be even more surprising: a catastrophic collision between two planets.
Tzanidakis himself expressed his astonishment at the ability of several telescopes to capture this impact at the exact moment in which it occurred, noting that there are very few records of planetary collisions of any kind and none with so many similarities with the impact believed to have given rise to the Earth-Moon system.
The possibility of observing more moments like this in other regions of the galaxy, adds the astronomer, would provide invaluable information about the formation of our own world.
The process of planetary formation involves the gravity aggregating matter — be it dust, gas, ice or rocky debris — orbiting a newly formed star. Solar systems in their early stages are chaotic environments, where planets frequently collide and explode, or are projected into space.
It is through this violent processover the course of about a hundred million years, that systems like ours end up reducing the number of planets and reaching a state of equilibrium.
Despite the presumed frequency of these collisions, observing them directly in a distant solar system requires an unusual combination of patience and luck. Planetary orbits must place bodies exactly between their star and us, so that collision debris partially blocks starlight.
In a previous study, Tzanidakis had already identified a system composed of a binary star and a large dust cloud that produced an eclipse lasting seven years. But Gaia20ehk’s behavior presented a unprecedented enigma.
The star’s specific fluctuation pattern, characterized by brief dips in brightness followed by a chaotic period, had never been observed before. The team had reached an impasse until James Davenport, lead author of the study, suggested that the team use data from another telescope to look for infrared light instead of visible light.
The comparison proved to be enlightening. Tzanidakis observed that the infrared light curve was the complete opposite of the visible light curve. While visible light began to flicker and decrease, infrared emission registered a sudden increase.
This evidence indicated that the material that blocked the star had a extremely high temperatureto the point of shining in the infrared. A planetary collision of a cataclysmic nature would certainly generate enough heat to explain this energy emission.
Furthermore, the right type of collision It could also explain the initial drops in light that had been detected. Tzanidakis advances the hypothesis that this initial behavior could have resulted from the two planets having reached each other agradually get closer to each other in a fatal spiral.
The detailed analysis of the star was on Wednesday at The Astrophysical Journal Letters.
