The Interstellar Comet 3I/ATLAS: A Cosmic Intruder

A traveler from beyond our Sun’s domain is currently making its way through the Solar System, providing scientists with a unique opportunity. Designated as 3I/ATLAS, this object is only the third confirmed interstellar visitor ever detected, and its brief appearance is already rewriting our understanding of comets forged around other stars.

The Discovery of a Galactic Drifter

The comet 3I/ATLAS was first identifies on July 1, 2025, by the Asteroid Terrestrial-impact Last Alert System, also known as telescope ATLAS, in Chile; and what makes it so unique is its peculiar trajectory, a hyperbolic orbit, which immediately marked it as an interloper, meaning it’s not gravitationally bound to the Sun and is simply passing through before heading back into the Milky Way galaxy. The name 3I confirms its status as the third interstellar object following the famous “Oumuamua” and “Borisov”.

“Every time we find one of these objects, it’s like receiving a free sample from a distant star system”, explained a Chris Lintott, a scientist involved in the tracking.

A Glimpse into its Ancient Past

Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI)

Astronomical observations, including those from the powerful Hubble and James Webb Space Telescope, have been crucial in studying this unique visitor. Scientists estimate that 3I/ATLAS could be at least 7 billion years old, potentially making it the oldest object ever observed, and suggesting it originated in the thick disk of the Milky Way, home to some of the galaxy’s most ancient stars. This fact is very important to the scientific community because it potentially makes it twice as old as our own Solar System.

Also, the comet began exhibiting signs of activity when it was still far from the Sun, so this early behavior points to a composition rich in highly volatile ices, particularly carbon dioxide (C02) and carbon monoxide (CO), which sublimate at much lower temperatures than water ice. This unusual chemical profile offers a stark comparison to many of the comets native to our Solar System. An important part of this comet is its physical characteristics because while its solid nucleus is small, likely only a few kilometers across, images show a distinct, bright coma, which is the cloud of gas and dust escaping its icy core.

Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI)

Can We See It from Earth?

The good news for us is that, according to official sources like NASA, the 3I/ATLAS doesn’t represent a threat to our planet. Scientists confirm the comet reached its closest point to the Sun (or perihelion) just a few days ago, on October 30, 2025. Even at its closest approach to Earth, the comet remained a safe distance away, at about 270 million kilometers.

While it was too faint to be seen with the naked eye, it became a prime target for large, amateur ground-based telescopes and advanced orbital observatories. Missions orbiting Mars and satellites monitoring the Sun also played a crucial role in tracking the comet as it passed behind the Sun from Earth’s perspective.

Image Retrieved from the China National Space Administration.

Now, as 3I/ATLAS now speeds away from the Sun, it will continue its boundless journey back into the interstellar medium, having gifted humanity an invaluable dataset on the architecture and materials of distant star system.