It’s old
Initial studies suggest that 3I/ATLAS may be between 3 and 14 billion years old, potentially meaning that it’s older than the Solar System (which is 4.6 billion years old). This would also make it the oldest comet yet seen.
We don’t know where it came from
While astronomers can pinpoint the direction from which 3I/ATLAS came into the Solar System, this doesn’t tell them where in the galaxy it originated. It’s not as simple as tracing a straight line — if this object has been travelling through space for millions of years, its trajectory will have been nudged countless times by stars, molecular clouds, even the spiral arms of the galaxy itself.
What we can deduce is that it likely started off in orbit around a star. Researchers think 3I/ATLAS was likely flung out of its star system by a close encounter with a giant planet or another nearby star. Observations by the space telescopes JWST and SPHEREx have shown that the comet is rich in carbon dioxide, which suggests that it formed far from its parent star, where temperatures are cold enough for carbon dioxide to become a solid.
We do know where it’s going
3I/ATLAS is heading toward the Sun at the time of writing, and will reach perihelion (its closest point to the Sun) around Oct. 29, 2025, at a distance of about 1.4 astronomical units (210 million kilometers, or 130 million miles), just inside the orbit of Mars.
After perihelion, it will pass 0.65 astronomical units (97 million kilometers; 60 million miles) from Venus on Nov. 3, 2025. Soon after that, the European Space Agency’s Juice (Jupiter Icy Moons Explorer) spacecraft that is en route to Jupiter will attempt to observe 3I/ATLAS using its cameras, spectrometers, and a particle sensor.