A group of astronomers made a revolutionary discovery when they detected molecular activity on comet C/2014 UN271 (Bernardinelli–Bernstein). It is the largest active comet from the Oort Cloud in history and the second most distant.
C/2014 UN271 was discovered in 2014 when it was 4.3 billion km from the Sun, which is comparable to the distance to Neptune. The tailed guest flew in from the Oort Cloud, a huge reservoir of icy bodies located at the outer edge of the Solar System. It was discovered thanks to its enormous size. The diameter of the nucleus of C/2014 UN271 is estimated at 140 km, which exceeds the size of most known comets. For comparison, the average diameter of the famous Halley’s Comet is 11 km, and that of Churiumov–Herasymenko is 4 km.
To date, scientists have known little about the behavior of such cold, distant objects. In order to uncover the secrets of C/2014 UN271, they used the Atacama Large Millimeter/submillimeter Array (ALMA). The observations were made when the comet was at a distance of 16.6 AU—roughly halfway between the Sun and Neptune.
Thanks to ALMA’s high sensitivity and resolution, scientists were able to focus on the extremely weak signal from such a cold and distant object. In particular, radio telescopes have managed to detect complex and evolving streams of carbon monoxide escaping from the comet’s nucleus. This was the first direct evidence explaining its activity at such a great distance from the Sun.
In addition, ALMA measured the thermal signal of C/2014 UN271. This allowed scientists to refine the comet’s dimensions and the amount of dust surrounding its nucleus. The figures obtained are consistent with previous ALMA observations and confirm that this is the largest comet in the Oort Cloud ever discovered.
This discovery not only marks the first detection of molecular gas emission in this record-breaking comet, but also provides a rare opportunity to glimpse into the chemistry and dynamics of objects originating from the farthest reaches of the Solar System. As C/2014 UN271 approaches the Sun, scientists expect more and more frozen gases to begin evaporating, revealing even more information about the comet’s original composition and the early Solar System.
C/2014 UN271 will reach the perihelion of its orbit in 2031, approaching the Sun at a distance of 10.97 AU, which is comparable to Saturn’s orbit. After that, it will begin its return journey to the Oort Cloud. According to various estimates, the comet will return to the inner part of the Solar System in 2.8–4.5 million years.
According to Phys.org
