Interstellar Comet 3I/ATLAS Reveals Origins in Distant Star's Outer Disk
The third interstellar object ever detected, 3I/ATLAS, has passed Jupiter's orbit and is leaving the solar system. Discovered on July 1, 2025, the comet-like body was studied by telescopes worldwide. New research posted on arxiv.org used the James Webb Space Telescope to analyze its dust, finding almost no crystalline silicates, indicating formation in the cold outer reaches of its home star's protoplanetary disk. Additional observations from ALMA and Webb show elevated levels of carbon monoxide, carbon dioxide, methane, and heavy water, with a deuterium-to-hydrogen ratio 30 times higher than solar system comets, suggesting formation below -405°F. Carbon isotope ratios hint at an origin 12 billion years ago. The comet is about 1.5 miles wide and may be the oldest planetary body ever seen. Scientists advocate for future interceptor missions like ESA's Comet Interceptor, set for 2028/2029, and the Vera C. Rubin Observatory may spot more interstellar objects.
Key facts
- 3I/ATLAS is the third interstellar object discovered in our solar system.
- It was discovered on July 1, 2025.
- The object has passed Jupiter's orbit and is leaving the solar system.
- Webb observations show almost no crystalline silicates in its dust.
- ALMA measured heavy water ratio 30 times higher than solar system comets.
- Formation temperature estimated below minus 405 degrees Fahrenheit.
- Carbon isotope ratios suggest formation up to 12 billion years ago.
- The comet is approximately 1.5 miles wide.
Entities
Artists
- Karen Meech
- Matthew Belyakov
- Luis Manzano
Institutions
- University of Hawaii
- Caltech
- University of Michigan
- European Space Agency
- James Webb Space Telescope
- Atacama Large Millimeter Array (ALMA)
- Vera C. Rubin Observatory
- International Gemini Observatory
- NOIRLab
- NSF
- AURA
- University of Alaska Anchorage
- UCLA
- Shanghai Astronomical Observatory
- STScI
Locations
- Hawaii
- Chile
- Milky Way