The interstellar comet 3I/ATLAS is now receding from Earth after making its closest approach on Friday, December 19th, passing within 168 million miles of our planet. This event marks the end of a rare opportunity for scientists to study an object originating outside our solar system. The comet will continue its journey through the Milky Way, leaving behind valuable data about the early conditions of other star systems.
A Third Interstellar Visitor
3I/ATLAS is only the third confirmed interstellar object observed passing through our solar system. The first was 1I/’Oumuamua (2017), followed by comet 2I/Borisov (2019). These encounters are crucial because they allow researchers to analyze materials that predate our own solar system’s formation, offering clues about the building blocks of planets and comets elsewhere in the galaxy.
Ancient Origins: A Comet Older Than Our Sun
What makes 3I/ATLAS particularly intriguing is its estimated age. Unlike comets from our solar system, which are typically around 4.5 billion years old, this visitor appears to be significantly older—possibly up to 7 billion years. This determination comes from its likely origin in the Milky Way’s “thick disk,” a region of stars that formed earlier in galactic history. As Oxford astronomer Matthew Hopkins stated, interstellar visitors “have the potential to be far older,” and 3I/ATLAS is statistically the oldest comet yet observed.
Unexpected Brightness and Lingering Questions
During its closest approach to the sun in late October, 3I/ATLAS exhibited an unusually bright flare. While comets typically brighten as solar radiation vaporizes their icy cores, this comet’s intensity exceeded expectations. The reason remains unknown, despite observations from multiple spacecraft—including STEREO-A, STEREO-B, and SOHO. Scientists are still analyzing the data to understand why this comet behaved differently from others, which could reveal new insights into the composition and behavior of interstellar objects.
Continuing Impact on Research
Even as 3I/ATLAS departs, the data collected will continue to inform astronomical research. The comet’s composition, brightness, and trajectory provide a unique snapshot of conditions in a distant region of the Milky Way.
“The reason for 3I’s rapid brightening…remains unclear,” scientists Qicheng Zhang and Karl Battams wrote, highlighting the ongoing mystery.
Researchers are using tools like NASA’s Eyes on the Solar System to track its progress, ensuring continued analysis of this exceptional interstellar traveler.
The study of these interstellar objects is more than just cataloging distant comets; it is a step toward understanding how other solar systems formed and what materials they hold.
