3I/ATLAS, the third confirmed interstellar visitor, recently passed its closest approach to the Sun and is currently on the Sun's far side from Earth, expected to reappear in December. Discovered by ATLAS in July, it was moving about 137,000 mph and will not come closer than ~170 million miles to Earth. Space telescopes (including Hubble) and spacecraft are collecting data; ESA’s JUICE will observe the object in November. While fringe theories about alien technology circulated, scientists say it is almost certainly natural and poses no threat.
Interstellar Comet 3I/ATLAS Just Passed Perihelion — What We Know Now
3I/ATLAS, the third confirmed interstellar visitor, recently passed its closest approach to the Sun and is currently on the Sun's far side from Earth, expected to reappear in December. Discovered by ATLAS in July, it was moving about 137,000 mph and will not come closer than ~170 million miles to Earth. Space telescopes (including Hubble) and spacecraft are collecting data; ESA’s JUICE will observe the object in November. While fringe theories about alien technology circulated, scientists say it is almost certainly natural and poses no threat.
01:01, 04.11.2025Science
3I/ATLAS: The latest on the interstellar visitor
3I/ATLAS, the third confirmed object known to have come from another star system, recently passed its closest approach to the Sun (perihelion) and is currently on the far side of the Sun from Earth. While hidden from ground-based telescopes for several weeks, space telescopes and spacecraft continue to gather data that scientists hope will reveal details about material formed around a different star.
Discovery and trajectory
The object was first detected in July by an ATLAS telescope in Chile (part of the NASA-funded Asteroid Terrestrial-impact Last Alert System) and reported to the Minor Planet Center. Follow-up observations established that 3I/ATLAS is almost certainly cometary in nature and originates from interstellar space. At discovery it was traveling about 137,000 miles per hour and is moving on a hyperbolic trajectory that will carry it back out of the solar system.
Closest approaches
- Closest approach to the Sun (perihelion): occurred around Oct. 30, at roughly 130 million miles from the Sun (for comparison, Earth is ~93 million miles from the Sun).
- Closest approach to Earth: about 170 million miles, so the object posed no threat to our planet.
Activity and observations
As it neared perihelion, astronomers expected 3I/ATLAS to shed mass as frozen surface gases sublimated, producing gas and dust in its coma and tail. A fleet of observatories — including NASA telescopes, ESA instruments and several Mars orbiters — have returned images and measurements. Hubble data helped constrain the nucleus size to a broad range of roughly 1,000 feet to 3.5 miles.
The European Space Agency’s JUICE spacecraft is scheduled to observe the comet between Nov. 2 and Nov. 25, a period when the object is expected to be especially active following perihelion. Because JUICE was observing from the opposite side of the Sun, the agency expected to receive those data some weeks later.
Public reaction and hypotheses
3I/ATLAS has attracted wide public interest, partly because Harvard astrophysicist Avi Loeb suggested the possibility — however unlikely — that the object could be artificial. Loeb has also stated that the object is “most likely a comet of natural origin,” but he argues that extraordinary possibilities warrant careful study.
Public figures have amplified interest: for example, Kim Kardashian asked NASA’s acting administrator about the object on social media; NASA replied that there is no evidence of aliens and that the comet poses no threat to life on Earth.
Why scientists care
Because 3I/ATLAS originated around another star, it offers a rare opportunity to study material that formed under different conditions than our own solar system. Astronomers are racing to collect spectra, images and other measurements while the comet is accessible.
In short: the comet has passed perihelion and is temporarily hidden from Earth, but continued observations from space promise new insights into interstellar material.