An enormous comet, designated as C/2014 UN271 (Bernardinelli-Bernstein), is making its way toward the inner Solar System, and astronomers have confirmed its massive size and activity. This colossal comet measures approximately 137 kilometers (85 miles) wide, making it the largest known Oort Cloud comet ever identified. Notably, it is significantly larger than the asteroid believed to have caused the extinction of the dinosaurs, which had a width of around 10 kilometers (6 miles).
The impending arrival of the comet could elicit concern due to its immense scale; however, astronomers assure that it will not venture closer than the orbit of Saturn when it reaches its closest approach on January 29, 2031.
Fresh observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have revealed striking outbursts of carbon monoxide emanating from the comet’s surface. “These measurements give us a look at how this enormous, icy world works,” remarked astrochemist Nathan Roth from American University and NASA Goddard Space Flight Center. Roth emphasized that such explosive outgassing patterns raise intriguing questions about how the comet might evolve during its journey through the Solar System.
ALMA’s observations, conducted on March 8 and 17, 2024, occurred after the comet exhibited significant outbursts. The initial observation captured the comet displaying heightened activity, with jets of gas mainly composed of carbon monoxide. The team also noticed the early formation of a coma, which is the cloud of dust and gas that envelops comets and contributes to their tails.
By the second observation on March 17, the comet exhibited a more subdued reaction with only a single jet visible, though the researchers speculate that the second jet may have rotated out of sight. Notably, the previous appearance of the coma was no longer observed.
While prior observations hinted at the existence of a coma, this study marks the first definitive detection of jets of gas emitted by UN271. Impressively, these observations were made from a distance of about 16 times the distance between Earth and the Sun, just inside the orbit of Uranus.
Previous estimates of the size of UN271’s nucleus, which confirmed its status as the largest Oort Cloud comet, stood at around 137 kilometers across. This size comfortably surpasses the previous record-holder, comet Hale-Bopp, which is just over half the size.
Although other comets may exceed un271 in sheer width, such as 95P/Chiron at more than 210 kilometers wide, it remains an astronomical rarity as it doesn’t traverse the inner Solar System but maintains a stable orbit between Saturn and Uranus.
As comet UN271 continues its approach, scientists are eager to further analyze and understand its behavior in the coming years. While the comet won’t be visible to the naked eye from Earth, its journey promises to offer spectacular views through telescopes, capturing the fascination of astronomers and enthusiasts alike.
The findings related to comet C/2014 UN271 were published in The Astrophysical Journal Letters.
