Potentially dangerous comets can be detected many years in advance if we follow the meteoroid trails they leave near Earth.
There are many comets that visit the Solar System quite frequently, at least on a cosmic timescale. Halley’s Comet, for example, passes by our planet every 76 years.
There are others, like the A3 Tsuchinshan-ATLAS, which are much less frequent visitors. Some of these objects, born on the outer fringes of the Solar System, are long period comets (LPCs) which only come closer to the Sun every 200 years or so.
Despite being fascinating to astronomers, LPCs represent a challenge for planetary defense, given that objects of this type are estimated to cause even 6% of impacts on Earth. However, very few of those that reach potentially dangerous distances have been detected.
According to , this is why these comets can represent a large threat. An object approximately one kilometer in diameter, for example, when hitting the Earth at a speed of 50 km/s, would release energy equivalent to 750 thousand megatons of TNT.
To increase the probability of detecting these bodies, a recent one, accepted for publication in The Planetary Science Journal and available on arXiv, proposes observing the meteoroid trailas they follow the orbits of LPCs and remain relatively stable over time.
When Earth crosses these tracks, meteoroids can enter the atmosphere and create meteor showers. Analyzing this trail makes it possible to calculate the direction and speed of meteoroids, which allows identify the orbit of the parent comet.
To test the method, scientists analyzed 17 meteor showers associated with known LPCs. They then created synthetic comets and placed them at distances where they would be visible by the LSST instrument – the world’s largest digital camera installed at the Vera C. Rubin Observatory – and compared the positions of the real comets with the models.
The results were promising, with most real comets were in the predicted areas by the models. The technique therefore makes it possible to identify potentially dangerous comets billions of kilometers away, years in advance.
The next step is to use this technique to hunt for “orphan” LPCs, that is, those that have left meteoroid trails but whose parent comets have not yet been found.
