Astronomers have learned to identify hazardous comets by analyzing meteor showers.

A meteor shower is a "rain" of fragments from comets and asteroids. As they approach the Sun, they begin to lose material due to heating, and this is not limited to the spectacular comet tail. The expelled material from the tail scatters along the "path" behind the comet and remains there. Thus, a diffuse trail of fine "gravel" stretches across the entire orbit of the comet or asteroid.

The Earth's orbit intersects with a considerable number of cometary and asteroidal orbits. This means that each year it passes through various trails left by these small bodies. When this occurs, the planet attracts all these tiny rocks, and we observe them as meteors.

This explains why each meteor shower occurs at the same time each year. Depending on the position of the trail relative to Earth, it enters it in such a way that the "stars" appear to be "falling" from a specific location in the sky. This location is called the radiant. Therefore, meteor showers are named after the constellations from which they appear. For instance, the Orionids occur in October-November. It’s easy to guess which constellation to look for them in. These are fragments of the famous Halley's Comet, which last visited us in 1986 and will return again in 2061.

In total, astronomers have currently identified a "kinship" of 17 comets and asteroids with certain meteor showers. Interestingly, the same celestial body can be responsible for two different meteor showers, because Earth passes through its trail twice. The same Halley's Comet, in addition to the Orionids, also produces the May Eta Aquariids.

The problem is that there are over 500 known meteor showers. This means that the "parents" of most of them have not been established. Almost all of the one and a half dozen identified are short-period comets that we know well and observe every few decades. However, with long-period comets, the significant issue is that they may appear only once every few thousand years. Therefore, it is likely that many of them have gone unnoticed by humanity throughout its existence.

In this scenario, no one can guarantee that the path of any comet currently flying toward us does not lead directly to its impact with Earth. It is worth mentioning that comets smaller than one kilometer are extremely rare, so we are talking about quite substantial chunks. According to rough estimates, if such an average body were to fall, it would result in an explosion equivalent to 750,000 megatons of TNT.

Consequently, a team of astronomers from the USA recently set out to investigate the "lineage" of meteor showers for which "parents" have not yet been found, for the sake of global peace of mind. In an article available on the preprint server arXiv.org, the scientists explained that this is absolutely possible.

The researchers decided to "pretend" that they were unaware of the 17 already identified "culprits" of the meteor showers and attempted to calculate them solely based on the characteristics of the showers themselves. By examining the properties of each meteor shower, they constructed a profile of the cometary or asteroidal trail from which it originates. The "arc" of this trail ultimately allows for the drawing of a complete ellipse of the celestial body's orbit and even, as the astronomers explained, determining its approximate location on this orbit. It turned out that in all 17 cases, the calculations were quite accurate, meaning that the "hosts" of the meteor showers were successfully identified.

Moreover, this method also confirmed the origin of another meteor shower — the Sigma Hydrids. It occurs from November 22 to January 4 and is observed in the constellation Hydra. There were suspicions that this shower is composed of fragments from the recently discovered comet Nishimura C/2023 P1. By the way, it is a long-period comet and will return in 2430.

It was found that the "traces" of the Sigma Hydrids indeed lead to it. Interestingly, this comet was spotted by a Japanese amateur astronomer in 2023 less than a month before it reached perihelion (the closest point to the Sun in its orbit), meaning it was practically "on the eve" of its arrival. The meteor shower could have been used to predict its arrival eight months earlier.