In the same way that an archaeologist can never give us the name of the potter who made a vessel, but can say that the clay came from a certain valley and that it was fired with a technique specific to a certain region, experts in galactic archeology They cannot point to a solar system as the precise origin of an object, but they can analyze its chemistry to locate possible candidates and rule out others. This is possible thanks to the presence of certain elements. The good thing is that the candidates are reduced as the object reveals the amount of each of these elements. It is as if it shows us an astronomical fingerprint. And that is what a team of NASA scientists are doing who have published a new study in Nature.
Just a few years ago, an object like 3I/ATLAS would have been little more than an astronomical curiosity: a visitor from another star that briefly crossed the solar system before being lost forever in the vastness of space. In fact, his two “putative brothers”: 1I/Oumuamua and 2I/Borisov, were little more than that. And now, more than 50 times the distance that separates us from the Sunare practically impossible to study in detail. 3I/ATLAS, however…
not only It can be confirmed that it comes from another planetary system, and also reconstruct the place in the galaxy where it was born.. The authors of the study, led by Martin Cordiner, analyzed the chemical composition of this comet and point out that it comes from a planetary system formed about 12 billion years ago, very close (in astronomical terms) to the origin of the universe.
Comets are true time capsules. They form during the birth of a planetary system and remain frozen for billions of years, preserving practically intact the composition of the gas and dust from which its star and its planets were born. Most of the comets that we know of belong to the solar system. However, 3I/ATLAS was expelled from its home system by gravitational interactions and has traveled through interstellar space until it crossed paths, by pure chance, with our cosmic neighborhood.
To find out where it came from, Cordiner’s team turned to a well-known tool in astronomy: spectroscopy. When the Sun heats the comet’s nucleus, part of its ice sublimates and forms a gas envelope known as a coma. The molecules present in that cloud absorb and emit light at very specific wavelengths, creating a kind of chemical barcode.
By analyzing this pattern, scientists can identify what substances the comet contains and in what proportions. The results reveal that 3I/ATLAS has a different composition than that observed in most comets in the solar system. Among other characteristics, it appears to be extraordinarily rich in water ice, to the point that the authors consider it one of the most abundant interstellar objects detected so far.
The Milky Way does not have the same chemical composition in all its regions. Near the galactic center, where more stars have been born and died over billions of years, certain heavy elements are abundant. In the outer regions, the chemistry is different. When a planetary system forms, comets incorporate that chemical composition and keep it frozen for billions of years. That means that each comet carries with it a kind of chemical DNA from the place where it was born. Thanks to models of the chemical evolution of the galaxy, the authors conclude that 3I/ATLAS probably originated in a region other than that of the Sun, possibly closer to the center of the Milky Way, where the chemistry of the interstellar medium was different.
“These signatures indicate formation at temperatures in a relatively metal-poor environment – notes the study -. When interpreted using galactic chemical evolution models, carbon isotopic composition implies that 3I/ATLAS may have accumulated 12 billion years agoafter a period of early and intense star formation. 3I/ATLAS thus represents a preserved fragment of an ancient planetary system.”
Cordiner’s team does not yet know the exact star from which it came, but is already reconstructing its “galactic neighborhood”, just as an archaeologist can point out a culture and even a city, analyzing the minerals used and the style. And this is fundamental to our knowledge: Until now, interstellar objects only demonstrated that other planetary systems existed. Now they are beginning to reveal what they were like.