Discovery of 3I/ATLAS: The Oldest Known Comet

• Scientists discovered 3I/ATLAS, an interstellar object, on July 1, 2025.

• The object’s highly elliptical orbit around the sun and its rapid movement through space indicate it’s interstellar.

• The path of 3I/ATLAS traced back to the direction of the constellation Sagittarius.

• The closest approach to Earth is about 270 million km, and it will exit the solar system in its hyperbolic orbit.

• Early observations confirmed 3I/ATLAS is an active comet with a visible coma and likely developing a tail as it approaches the sun.

• The nucleus of 3I/ATLAS is estimated to be about 10-30 km wide, larger than its interstellar predecessors, 1I/Oumuamua in 2017 and 2I/Borisov in 2019.

• 3I/ATLAS is likely to be the oldest comet scientists have ever observed, possibly predating the solar system itself by more than 3 billion years.

• Studying 3I/ATLAS could reveal unique details from the Milky Way’s galactic history and provide insights into the building blocks of planets and star formation processes across the galaxy.

• A global campaign is underway to monitor 3I/ATLAS as it passes through the inner solar system.