Was discovered in the solar system only two days ago, the 1 July 2025 from a telescope in Chile part of the project Atlas of NASA, but has already captured the attention of astronomers from all over the world: it’s called 3i/Atlas And it is the third interstellar object – that is, from another star system – never discovered. And not only that: it is a cometas confirmed by the astronomers who have already identified a hair and a small tail. The abbreviation “3i” in the name indicates precisely this: which is the third (3) Interstellate object (i) sighted in our sun system. Being the second interstellar comet Never discovered, it is a unique opportunity to obtain otherwise inaccessible information on the composition of other star systems. At the moment 3i/Atlas is located inside the orbit of Jupiter (670 million km away from the sun) and is approaching at great speed Sun: according to the calculations of the astronomers, it should reach the minimum distance from the sun (i.e. the perihelion) around the 30 October 2025while the December 19th will be at the point closest to the Earth.
The discovery of interstellar comet 3i/Atlas
The first observation of this object dates back to 1 July 2025when initially it was exchanged for a “normal” asteroid of the Solar System. But subsequent observations revealed two important characteristics of this little celestial body. First of all, the presence of a crown and a tail (3 -second 3 seconds long) has undoubtedly betrayed its comets.
But it was his trajectory that gave the biggest surprise: it was not in fact a orbit closed around the sun, as happens for any other body of the sun system, but one hyperbolic trajectorytherefore open: an unequivocal clue – together with the very high speed of 68 km/s – of the fact that comes from outside our star system. It is therefore an object that somehow has escaped from the gravity of its mother star and traveled into the interstellar space to the fortuitously intercepting the gravity of the sun.
In any case, the 3i/Atlas was not easy to discover: even if bright, in fact, the comet is precisely in the constellation of the Sagittarius, therefore in the direction of the center of the Milky Wayand it was therefore difficult to distinguish also given its weak brightness (the comet had a magnitude of +18 at the time of the discovery).
The trajectory of the 3i/Atlas: when it will approach the earth and how much it will be visible
In its long phase of approaching the sun, which lasts from millions of yearsthe 3i/Atlas has always remained in the constellation of the Sagittariusmoving at a speed of about 68 km/s. Now, however, it has entered theorbit of Jupiterabout 4.4 astronomical units away from the sun and 3.4 from the earth (1 astronomical unit is equal to the average distance between the earth and the sun, that is, about 150 million km).
In the coming months, accelerated by the gravitational attraction of the sun, it will increase its speed until you reach 77 km/sreaching Perdie around 30 October 2025 and reaching the minimum distance from the Earth on December 19, when it came into the constellation of the lion And it will be 240 million km from us (about 1.6 astronomical units).
According to NASA, the Comet 3i/Atlas can be visible for terrestrial telescopes until September, after which it will pass Too close to the sun In order to be observed by our tools. Only at the beginning of December will it reappear from the other side of the sun, allowing us to return to study it. In any case, it will not be possible to observe it naked eyebut it will serve medium power telescopes.
If you want to see it “preview” without moving from home, you can look from midnight on 3 July the direct observation of the new interstellar comet in the YouTube channel of the Italian project Virtual Telescope.
The other interstellar objects: 1i/’Oumuamua and the 2i/Borisov
It is not however the first interstellar object To visit our sun system: in 2017 a strange celestial body in the shape of a cigar was discovered, then called 1i/’Oumuamua. This, however, was not recognized as a comet: the celestial object, in fact, had properties more similar to those of a asteroid and did not show the emissions of gas and dust typical of a comet.
Being then of the first recorded case of an interstellar object, the event created different speculation on its origin: according to scholars, the celestial body could also have been the fragment of a Nano planetwhile the most imaginative even raised the hypothesis on a possible alien origin.
In 2019, however, it was the case of Comet 2i/Borisov: Unlike the previous one, for scholars it was immediately possible to identify the comets that hid the nucleus. Precisely for this reason, the interstellar object mobilized scholars from all over the world, who tried to identify similarities and differences between the comet of our solar system and those originating in a different environment.
