The ATLAS (short for Asteroid Terrestrial-impact Last Alert System) is a NASA-funded program developed by the University of Hawaii. It incorporates data from four ground-based telescopes, two in Hawaii, one in Chile, and one in South Africa, to scan the entire sky twice a night, looking for asteroids and other impactors.
In the course of their search for near-Earth objects, astronomers recently discovered a comet visiting from interstellar space. This is only the third interstellar object ever discovered, following ‘Oumuamua and Comet 2I/Borisov. Each of these interstellar visitors offers a chance to learn about another star system without having to go there ourselves, like the ill-fated crew of SYFY‘s The Ark (streaming now on Peacock).
An interstellar comet called 3I/ATLAS is visiting our solar system
The newly discovered comet, dubbed 3I/ATLAS, is coming from the direction of the constellation Sagittarius and was about 420 miles away from the Sun when it was spotted on July 1. Following the discovery, astronomers looked through historical telescope images and found pre-discovery observations going back to June 14, 2025.
Those observations, and others in the days since, helped to figure out the object’s orbit and confirm its interstellar origin. We know 3I/ATLAS is interstellar because it has a highly eccentric orbit. Eccentricity refers to how close an object’s orbit is to a perfect circle. A perfectly circular orbit would have an eccentricity of 0, and the more elliptical or squashed it is, the closer its eccentricity is to 1. An eccentricity beyond 1 means the orbit is hyperbolic and not bound to the Sun. The eccentricity of 3I/ATLAS is about 6, clearly demonstrating that it came from interstellar space and, after a short visit to our solar system, will soon return to it.
Where 3I/ATLAS came from and where it’s headed
The interstellar comet 3I/ATLAS is currently inside the orbit of Jupiter (although on the other side of the solar system from the massive gas giant) and headed toward the inner solar system. It will make its closest approach to the Sun in October, passing between the orbits of Earth and Mars, before heading back out of the solar system and into interstellar space once more.
Don’t worry though, it’s no threat to Earth. It will stay a cozy 150 million miles away from our planet as it passes through our solar system. It’s still early days and astronomers are busily observing 3I/ATLAS while it’s in town. It will remain visible to ground telescopes through September of this year, before getting too close to the Sun to be seen. It will come around the other side in Early December, when astronomers will be able to observe it again until it gets too far away to see.
At present, astronomers estimate it’s a comet between 6 and 19 miles wide. Either way, it’s the largest interstellar object we’ve seen so far. It’s also absolutely cruising and getting faster. Astronomers calculated its speed at about 137,000 miles per hour when it was discovered. As it approaches the Sun, gravity will accelerate it to an estimated 152,000 miles per hour.
The discovery is a valuable opportunity for astronomers to learn more about other star systems. While we won’t be able to catch up with 3I/ATLAS and study it directly, astronomers can learn about its chemical composition from a distance. If we ever do have to hop an ark to another star system, we might actually know a little more about them, thanks to objects like 31/ATLAS.
In the meantime, you can catch up with the first two seasons of The Ark, streaming now on Peacock.
