NASA and the International Astronomical Union’s Minor Planet Center have confirmed that a newly detected comet, now designated 3I/ATLAS, is on a hyperbolic trajectory through the solar system, making it only the third known interstellar object after 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019.
The object was first spotted on 1 July by the NASA-funded ATLAS survey telescope in Rio Hurtado, Chile. Subsequent analysis of archival images pushed its observational record back to 14 June, enabling precise orbit calculations and the formal ‘3I’ (third interstellar) designation issued this week.
3I/ATLAS is currently about 670 million kilometres from Earth, travelling roughly 59 kilometres per second—fast enough to escape the Sun’s gravity. Photometric data indicate a nucleus between 20 and 25 kilometres wide surrounded by a faint coma and tail, confirming its cometary nature.
Models show the comet will reach perihelion on or about 30 October, passing just inside Mars’s orbit at 1.4 astronomical units from the Sun. Even at that point it will remain at least 150 million miles from Earth, and astronomers stress that it poses no impact risk.
Because 3I/ATLAS was detected months before its closest approach, observatories worldwide—including Hubble and the James Webb Space Telescope—have time to study material formed around another star. ESA said the event underscores the value of its planned 2029 Comet Interceptor mission and signals that enhanced survey coverage is beginning to reveal the population of interstellar wanderers thought to permeate the Milky Way.
