The Telescopio Nazionale Galileo observes with NICS the new interstellar visitor, 3I/ATLAS

The Telescopio Nazionale Galileo (TNG), at the Roque de los Muchachos Observatory (La Palma), did not miss the opportunity to observe the new interstellar object whose discovery was announced on July 1, 2025.

This visitor, named 3I/ATLAS, follows in the footsteps of its predecessors, 1I/‘Oumuamua and 2I/Borisov, discovered in 2017 and 2019. Like them, it was detected on its journey toward the Sun, on a hyperbolic orbit at high speed (about 60 km/s) when it was still 3.3 AU from our star (about 495 million km). Shortly after the announcement of its discovery by the ATLAS telescopes, its cometary nature was confirmed thanks to the coma surrounding its bright nucleus.

Excitement quickly grew: telescopes around the world and space missions turned their gaze toward this peculiar visitor. The TNG was no exception. As it did in 2019 with Borisov, it has obtained infrared images and spectra to study the composition and evolution of the coma. “Infrared images will allow us to measure the extent of the dust cloud and analyze its colors, while the spectra could reveal how that suspended dust modifies the sunlight reflected by the nucleus,” said V. Lorenzi astronomer at the TNG.

At this moment, 3I/ATLAS is heading toward its closest approach to the Sun, expected on October 29, 2025, at just 1.36 AU. After perihelion, the object will become visible again at the end of November in the early morning sky, disappearing with sunrise, and its brightness will be about 20 times greater than in July.

The analysis of observations obtained with NICS (Near Infrared Camera Spectrometer) installed at TNG, before and after perihelion will allow close monitoring of how its coma evolves, shaped by the gases escaping from the nucleus and by the pressure of solar radiation. These studies, common for comets in our own system—as well as those carried out by the TNG on Borisov by the same research team—now offer a unique opportunity: to determine whether comet formation processes around other stars are universal, or if they reveal notable differences compared to those we know in our “cosmic neighborhood.”

Time-lapse sequence of near-infrared images of interstellar comet 3I/Atlas, obtained using NICS in the J-band filter (2025 August 07). The comet is seen moving across the field of view against the background stars.