Astronomers from the Atacama Large Millimeter/Submillimeter Array (Alma) have made observations of comet C/2014 UN271 (Bernardinelli-Bernstein).
C/2014 UN271 was identified by astronomers Pedro Berner Dinnelli and Gary Bernstein through images captured in 2014 as part of dark energy research.
The comet spans approximately 140 km (85 miles) in diameter, making it over ten times larger than any known comet.
To date, little has been understood about the behavior of such cold, remote celestial bodies.
Recent findings from Alma revealed the intricate and dynamic jets of carbon monoxide gas erupting from the comet’s nucleus, offering the first direct evidence of what drives its activity in relation to the sun.
“With these measurements, we can understand how this massive, icy world functions,” stated Dr. Nathan Ross, an astronomer affiliated with a U.S. university and NASA’s Goddard Space Flight Center.
“We are observing explosive outgassing patterns that raise new inquiries about the comet’s evolution as it journeys deeper into the inner solar system.”
Alma observed C/2014 UN271 by detecting light from carbon monoxide gas in its atmosphere and thermal radiation when the comet was still distant from the sun.
Thanks to Alma’s exceptional sensitivity and resolution, scientists were able to focus on the very faint signals emitted from such cold and far-off objects.
Building on previous Alma observations that characterized the comet’s substantial nucleus size, the new findings measured the thermal signal to accurately assess the size of the comet and the dust surrounding its nucleus.
Their measurements for the nucleus size and dust mass are in line with earlier Alma observations, affirming it as the largest cloud comet ever identified.
Alma’s precision in measuring these signals enabled this research, providing a clearer understanding of this distant, icy giant.
“This discovery not only represents the first detection of molecular outgassing in a record-setting comet but also offers a rare glimpse into the chemical and dynamic processes of objects from the farthest reaches of the solar system,” the astronomer added.
“As C/2014 UN271 approaches the sun, we anticipate more frozen gases will start to evaporate, revealing further insights into the comet’s primitive composition and the early solar system.”
“Such discoveries help address fundamental questions about the origins of Earth and its waters, as well as the formation of life-supporting environments elsewhere.”
The team’s research paper was published in Astrophysics Journal Letters.
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Nathan X. Ross et al. 2025. Initial detection of molecular activity in the largest known OORT cloud comet: Alma Imaging of The Sun at C/2014 UN271 (Bernardinelli-Bernstein). apjl 986, L22; doi: 10.3847/2041-8213/add526
Source: www.sci.news
