The telescope’s observations of the Interstellar Comet 3i/Atlas have shown it resembles a comet found beyond our solar system. Intriguing aspects, like the substantial amounts of water detected even far from the sun, may shed light on the ancient stellar system from which it originated.

Objects from other solar systems that pass through ours are extremely rare. Discovered in July, 3i/Atlas is the third such interstellar visitor, following Oumuamua in 2017 and Borisov in 2019. Remarkably, its visit has only been a few months long.

Scientists speculate that its high speed may indicate that it originates from a star system billions of years older than our own. Initial estimates suggested it has a diameter of approximately 20 kilometers, but details about the extensive plume of water and gas remain limited.

Toni Santana Ross from the University of Barcelona and colleagues have utilized ground-based telescopes to observe the comet and its tail, finding it contains moderate amounts of dust. Notably, the dust appears to increase as the comet approaches the sun, mirroring patterns seen in comets from our outer solar system. “It’s a typical object; there’s nothing particularly strange about it,” states Santana Ross.

Astronomers have also monitored comets via space. Researcher collaborating found that the Hubble Space Telescope might estimate the comet’s size between 320 meters and 5.6 kilometers, and it likely started off much smaller.

Comets usually contain ice, which vaporizes as they near the sun, creating water vapor in their tails. Utilizing the Neil Gehrels Swift Observatory Satellite, Zexi Xing from Auburn University has detected water in the comet’s tail located significantly farther from the sun than is typical for comets. The amount of water detected suggests that about 20% of the comet’s surface is responsible for this production, exceeding typical solar system comet proportions.

Such prolific water generation may indicate that 3i/Atlas originates from a star system much older than ours, hypothesizes Cyrielle Opitom at the University of Edinburgh. This is due to older stellar systems generally having higher water content compared to other molecules. “It might be that because it formed earlier, it retains more water than other molecules, but it’s premature to reach a conclusion,” she remarks.

Astronomers are also scouring historical data to determine if the telescope mistakenly detected a comet. Adina Feinstein and her team at Michigan State University have found that the transit exoplanet survey satellite (TESS) was operationally searching for planets around other stars and incidentally captured a comet between May 7 and June 3. “It just happened that we were observing the exact region where 3i/Atlas was at that moment,” says Feinstein.

The comet was found to be surprisingly bright at that time, suggesting it was releasing significant amounts of water or gas even at considerable distances from the sun. “We didn’t detect transits in regions of our solar system where water would typically start to react,” highlights Feinstein.

In this distant region, the likelihood of finding water is low, with gases such as carbon monoxide and carbon dioxide being more common, according to Opitom. “This is a pattern seen in comets from our solar system; they can exhibit activity at much greater distances due to these volatile materials.”

Yet, the fact that it was active so far from the sun could indicate that this comet has not been significantly exposed to starlight throughout its life, notes Matthew Jenge from Imperial College London.

“What this implies is that this comet was ejected from the fringes of another solar system,” Genge describes. While the exact cause of its ejection is uncertain, it’s possible that gravitational forces from a nearby star could have set it on a trajectory towards us, he explains.

Opitom mentions that the James Webb Space Telescope has recently conducted its observations and that astronomers will analyze the data in the upcoming weeks, promising more insights into 3i/Atlas soon.

As comets approach their closest point to the sun in October, astronomers will have the opportunity to measure the gases they emit. This will provide important insights not only into the characteristics of the comet itself but also into the composition of the molecules in its active tail, which may reveal details about the formation of 3i/Atlas, according to Opitom.

Similar to previous interstellar objects, speculations about potential alien technology exist, but Santana Ross has found no supporting evidence. “If you take a holiday photo and see something tall with a long neck and four legs, you might think of it as an alien, but it’s most likely a giraffe,” he quips. “There’s no reason to believe this is anything unusual or evidence of something extraordinary.”

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