Our third interstellar visitor might be 8 billion years old
The trajectory of the interstellar comet 3i / atlas when it goes through the solar system
NASA / JPL-CALTECH
An interstellar object that currently crosses our solar system could be one of the oldest comets we have ever seen, from a star of billions of years more than ours.
The 3i / Atlas comet was spotted earlier this month near the orbit of Jupiter, moving around 60 kilometers per second and estimated at 20 kilometers in diameter. This is the third known interstellar object found in our solar system, and will spend near March in October before moving away from our sun.
Matthew Hopkins at the University of Oxford and his colleagues modeled the comet’s speed and trajectory to determine where they came from, using data from the Gaia space spacecraft which has mapped a billion stars in our galaxy. It seems that it is from a region of our 13 billion years galaxy, called the thick disc, containing older stars and seated above the thin disc in which our orbit sun.
“Thick disc items are faster,” said Hopkins, while the two previous known interstellar objects – Oumuamua in 2017 and Comet Borisov in 2019 – were slower. “Their speeds were what we expect for a thin disc object.”
Team modeling suggests that 3i / Atlas comes from a star that has at least 8 billion years, almost twice the age of our sun, and perhaps even older. “It could be the oldest comet that we have ever seen,” says Hopkins. It is believed that interstellar objects are more likely to be ejected at the start of the life of a star, perhaps thrown by passing stars or interactions with giant planets.
Ancient stars are likely to have a lower metal content than our sun, which would also cause a higher water content for their comets, explains Hopkins. If this is true, we could start to see large amounts of water spitting the comet as the sun approaches in the coming months.
It would probably be his first meeting with another star, giving us an overview of billions of years of virgin materials more than the earth. “We believe most of the interstellar objects that we see meet a star for the first time, even if they are 8 billion years old,” explains Hopkins. “They would have wandered in deep spaces until they get closer to us.”
Subjects:
