The Oldest Interstellar Comet: Comet 3I/ATLAS
The trajectory of interstellar comet 3I/ATLAS as it passes through the solar system
NASA/JPL-Caltech
An interstellar object known as Comet 3I/ATLAS is currently traversing our solar system, and scientists believe it may be one of the oldest comets ever observed, originating from a star that predates our own sun by billions of years.
First detected near Jupiter’s orbit, Comet 3I/ATLAS measures approximately 20 kilometers across and is moving at an impressive speed of 60 kilometers per second. This comet marks the third interstellar object identified within our solar system and is expected to make a close pass by Mars in October before continuing its journey away from our sun.
Researchers, led by Matthew Hopkins from the University of Oxford, analyzed the comet’s trajectory and velocity using data from the European Space Agency’s Gaia spacecraft, which mapped a vast number of stars in our galaxy. Their findings indicate that Comet 3I/ATLAS likely originated from the thick disc region of our galaxy, known for containing older stars compared to the thin disc where our sun resides.
According to Hopkins, thick disc objects like Comet 3I/ATLAS tend to exhibit higher velocities, distinguishing them from prior interstellar objects such as ‘Oumuamua and Comet Borisov, which displayed slower speeds. Based on their calculations, the team suggests that this comet could have come from a star that is at least 8 billion years old, making it potentially the oldest comet ever observed.
It is theorized that interstellar objects are more commonly ejected from stars early in their lifecycle, possibly due to interactions with neighboring stars or giant planets. These older stars are likely to have lower metal content, leading to comets with higher water content. As Comet 3I/ATLAS approaches the sun in the coming months, scientists anticipate observing significant water emissions, offering a glimpse of pristine material that predates Earth by billions of years.
According to Hopkins, most interstellar objects encountered in our solar system are likely experiencing their first encounter with a star, despite their ancient origins. This encounter with our sun provides a unique opportunity to study materials that have been wandering through deep space for eons.
