Interstellar Comet 3I/ATLAS Traced to Cold, Isolated Region of Milky Way
Astronomers have determined that interstellar comet 3I/ATLAS likely originated from a cold, isolated region of the Milky Way, providing insights into early planetary formation conditions.
Astronomers have traced the origin of interstellar comet 3I/ATLAS to a cold, isolated region of the Milky Way, suggesting it formed in an environment vastly different from our solar system.
Discovered in July 2025 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile, 3I/ATLAS is only the third confirmed interstellar object to pass through our solar system.
A team led by the University of Michigan utilized the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study the comet. Their observations revealed high levels of deuterium, or heavy hydrogen, in the comet's water, indicating it formed in extremely cold conditions.
The study, published in Nature Astronomy, suggests that while our sun formed in a cluster of stars, the comet's parent star may have been more isolated, resulting in less cosmic heat.
Estimated to be up to 11 billion years old—more than twice the age of our sun—3I/ATLAS offers a unique glimpse into the early conditions of planetary formation in different regions of the galaxy.
After passing close to Earth in December 2025, the comet is now beyond Jupiter, traveling at approximately 137,000 mph (220,000 kph) as it exits our solar system.