Comet 3I/Atlas, a frigid wanderer that traversed our solar system last year, is believed to have originated from a chilly area of the Milky Way that has not yet developed its own solar system. Its path provides essential insights into the cosmic history that spans billions of years.
As the third verified interstellar object to enter our celestial vicinity, Comet 3I/Atlas may also be the most ancient, with age estimates suggesting it could be as old as 11 billion years—over double the lifetime of our sun. A team of researchers from the University of Michigan utilized the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to analyze this comet during its passage last autumn. First detected the previous summer, the icy entity permitted extensive observations as it flew past Mars in October and neared Earth in December. It has since moved beyond Jupiter and is now on a clear trajectory out of our solar system, remaining visible solely to professional astronomers.
The research uncovered a noteworthy amount of deuterium, or heavy hydrogen, within the comet’s water. This points to an origin significantly colder than the environment surrounding our sun during its formation. Teresa Paneque-Carreno from the University of Michigan noted, “While our sun may have been surrounded by other newborn stars as it was forming, this comet’s home star could have been more of a loner, leading to less heating and colder conditions.”
Although the precise birthplace of the comet remains unclear, observations from the Hubble Space Telescope suggest that its nucleus measures between 440 meters and 5.6 kilometers. Presently, it is racing through space at an incredible speed of 137,000 mph (220,000 kph), quickly departing our solar system.
By combining these data points, scientists aim to enhance their understanding of the conditions that existed during the formation of solar systems in the early universe. As Paneque-Carreno expressed in an email, piecing together all these “puzzle pieces together may give an idea to how the planet-forming conditions were at these early times.” The study of interstellar comets like 3I/Atlas could ultimately transform our understanding of planetary formation throughout the cosmos.
