It is the third interstellar object detected in our Solar System and one of the most sought-after celestial bodies by astronomers around the world these days. And this is how it appears in the mirror of the JAST80 telescope at the Javalambre Astrophysical Observatory: a comet speeding through a dense field of stars. The animation is the result of combining 20 images taken on the night of 14 to 15 July. The observations were made by a team consisting of David Morate, Héctor Vives-Arias, Héctor Vázquez Ramió, Alessandro Ederoclite and Alejandro Lumbreras-Calle. Most of them belong to the Javalambre Variability Survey (J-VAR) project for the detection of variable objects.

3I/ATLAS was detected on 1 July by the telescope belonging to the ATLAS network located in Río Hurtado, Chile. Together with 1I/Oumuamua (2017) and 2I/Borisov (2019), it is one of the few objects discovered in our Solar System that originated elsewhere in the Milky Way. According to experts, there are many more interstellar objects crossing our Solar System, but it is very difficult to capture an image of them. They are only visible if they are close enough and if the telescopes are pointed at the right place at the right time.

This comet, 3I/ATLAS, differs from the previous ones in that it is larger, with a diameter of approximately 20 kilometres (Oumuamua measured 200 metres), and faster, travelling at around 220,000 kilometres per hour. It poses no danger to Earth; when it comes closest, on 19 December, it will be 270 million kilometres away from us. And on 30 October, it will be at its closest approach to the Sun. Observations of its trajectory indicate that the comet does not revolve around the Sun, confirming that it comes from a star system other than our own. It could be a leftover fragment from the formation of a planetary system. The CEFCA is developing the J-VAR project, which observes regions of the sky already characterised by J-PLUS and revisits them up to 11 times, with a frequency that can vary from a few days to a year. Among the more than 6,500 objects observed, 17 near-Earth asteroids, two comets and five possible objects that had not been previously recorded have been detected. The results demonstrate the project's and the infrastructure's ability to detect minor bodies. In fact, CEFCA is already working on launching a project at the observatory with new capabilities focused on planetary defence and space debris.

3I/ATLAS located by JAST80, one of the telescopes of Javalambre Astrophysical Observatory. CREDIT: CEFCA/Alejandro Lumbreras.