The Oort Cloud is home to a mega-comet that could be the largest discovered. The unusual celestial wanderer, measuring 100200 km in diameter, will be closest to the Sun in 2031. It will be closest to Saturn's orbit, however.
Astronomers say Comet Bernardinelli-Bernstein (C/2014 UN271) could be the largest member of the Oort Cloud ever detected, and it is the first comet on an incoming path to be detected so far away.
Will Gater, an astronomer, has drawn the graphic below which compares the size and shape of the comet with other Solar System objects.
Pedro Bernardinelli and Gary Bernstein from the University of Pennsylvania discovered the comet earlier this year. They were looking through data from the 570-megapixel Dark Energy Camera, (DECam), on the Vctor M. Blanco 4 meter Telescope in Chile. The data was not typical of a comet tail and they found it in the original 2014-2018 data. They considered the object to be a dwarf planet.
Within a day of the Minor Planet Center's announcement, astronomers using Las Cumbres Observatory network captured new images. These images revealed that the object had grown a coma over the past 3 years and was moving quickly through the Oort Cloud. The object was officially designated a comet.
Bernstein and Bernardinelli began to study the comet with an astronomer crew. They collected data from all available observational sources. They have now posted a paper on Arxiv, with the unusual title of C/2014 UN271 (Bernardinelli-Bernstein): the nearly spherical cow of comets.
According to them, astronomers used backwards and astrometry to study the orbits of comets. This would suggest that it is a brand new comet. Its previous closest approach to Earth was about 3.5 million years ago.
The coma also appears to be showing the normal simple sublimation thermodynamics for most comets (hence the paper's spherical cow title). However, they cannot predict how brighter or more active it might become as it nears the Sun. Astronomers Telegram on September 14th indicated that the object had increased in brightness with an outburst at magnitude 20, 20 and 18.
Bernardnelli stated on Twitter that we were able to confirm that this is likely consistent with CO2 and NH3 sublimation but could not do more.
The coma is consistent using a stationary model and follows simple sublimation thermodynamics (hence, the title of the paper: spherical cow). This is consistent with either CO2 or NH3 sublimation. However, we couldn't do more.
(8/n) pic.twitter.com/0k8Lc4UuTG Dr. Pedro Bernardinelli (@phbernardinelli) September 22, 2021
Astronomers concluded that the comet's current inward journey began at a distance over 40,000 astronomical unit (au) from Sun. This is 40,000 times farther than Earth, or 6 trillion km (6 trillion miles or 0.6 light years 1/7 of the distance to nearest star). On average, Pluto is 39 au away from the Sun.
The comet is currently located about three billion kilometers away from Uranus, or 1.8 billion miles. Its magnitude is just below 20. It is predicted that the comet will not be visible to the naked eye even at the closest approach in 10 years. Only the most powerful amateur telescopes will be capable of seeing it.
Lead image caption: A graphic comparing the size of Comet 2014 UN271 (Bernardinelli-Bernstein) to other solar system objects. Copyright and credit to Will Gater. Permission granted
Continue reading:
Noirlab Press Release
Paper on Arxiv
