Key Highlights
- NASA’s Neil Gehrels Swift Observatory has detected hydroxyl (OH) gas from comet 3I/ATLAS, a major breakthrough in understanding how interstellar comets evolve.
- The discovery suggests that sunlight is heating small icy grains released from the comet’s nucleus, allowing them to vaporise and feed the surrounding cloud of gas at a distance far beyond where water ice normally turns into a gas.
- Comet 3I/ATLAS, one of only three interstellar comets known, is thought to be over 7 billion years old, making it potentially twice as old as Earth.
- The discovery has implications for studying the chemistry involved in planet formation beyond our Solar System and hints at the potential diversity in life-hosting planets across the galaxy.
New Insight into Interstellar Comet 3I/ATLAS: A Major Breakthrough
NASA’s Neil Gehrels Swift Observatory has made a groundbreaking discovery about comet 3I/ATLAS, one of only three known interstellar comets. The telescope detected hydroxyl (OH) gas from the comet at a distance far beyond where water ice normally turns into a gas due to solar radiation.
The detection is significant because it provides new insights into how interstellar comets evolve and behave in space. Previously, scientists had only studied Solar System comets, which orbit the Sun. The discovery means that they can now use similar criteria to study 3I/ATLAS, opening up a new avenue of research.
The Comet’s Unusual Journey
Comet 3I/ATLAS was discovered on July 1, 2025, by the ATLAS program at the University of Hawaii. Unlike other comets that orbit the Sun, this interstellar visitor is believed to have originated from another star system and entered our Solar System just a few years ago.
Its estimated age of over 7 billion years makes it one of the oldest comets ever observed, potentially twice as old as Earth itself. This unique characteristic sets it apart and provides valuable information about the early stages of planetary formation in other star systems.
Astronomers’ Excitement
The team behind the detection at Auburn University, led by Professor Dennis Bodewits, is particularly excited about their findings. “When we detect water—or even its faint ultraviolet echo, OH—from an interstellar comet, we’re reading a note from another planetary system,” Bodewits said in a statement.
The team observed 3I/ATLAS using the Swift Observatory within weeks of discovery, capturing crucial data before the comet grew too faint or close to the Sun for detailed observation. The observatory’s location above Earth’s atmosphere allowed it to see ultraviolet wavelengths that are almost completely absorbed on the ground, providing a unique perspective.
Implications for Planetary Science
The discovery of water activity at such a great distance from the Sun in 3I/ATLAS suggests an unusual process is occurring. One theory proposed by the team is that sunlight is heating small icy grains released from the comet’s nucleus, causing them to vaporize and feed the surrounding cloud of gas.
This finding has significant implications for understanding how interstellar comets behave and evolve over time. It also offers a rare opportunity to study the chemistry involved in planet formation beyond our Solar System.
Each interstellar comet that we observe helps rewrite what scientists thought they knew about planetary systems, hinting at the potential diversity of life-hosting planets across the galaxy.
As 3I/ATLAS fades from view but will become observable again after mid-November 2025, astronomers will continue to study it closely. This comet could provide valuable insights into the origins and evolution of comets in other star systems, contributing significantly to our understanding of the universe.
