Think of a snowball mixed with dust and tiny rocks but twice the size of the state of Rhode Island. This space snowball, aka a comet, is the most recently imaged object of this kind using the Hubble Space Telescope by a team of planetary astronomers led by Dr. Man-To Hui of the Macau University of Science and Technology, Taipa Macau. This work was recently published in a peer-review journal, Astrophysical Journal Letters.
Comets are snowballs made of frozen gases, dust, and rocks that orbit our Sun. Unlike planets, their orbits are usually highly elliptical. This means they could come as near as a few million miles from the Sun to a few billion miles when they are farthest away. These ancient cosmic snowballs provide direct insight into our Solar System during its primitive state. Usually, they develop a big tail (~million miles) pointing away from the Sun, when they come near it. This tail is made up of particles that burn or glow during their interaction with solar particles and for this reason, a comet’s tail is the longest when it is closest to the Sun.
This comet, called C/2014 UN271 was serendipitously discovered in 2014 by astronomers Pedro Bernardinelli and Gary Bernstein while they were looking at archival data for a different project that mapped out 300 million galaxies. Dr. Man-To Hui and his team took observations with Hubble to confirm its existence and they found the largest ever discovered comet to date, spanning approximately 80 miles in size. At present, it is quite far away from us, i.e., about 20 AU (1AU = distance of the Earth from the Sun), but it will approach us at its nearest distance in 2031. Fortunately, that distance is large enough that people on Earth don’t have to worry about it. The closest it will come to us will be approximately a bit larger than the distance between us and Saturn. After its closest approach, it will again circle back into deep space for millions of years.
Sources: Astrophysical Journal Letters, NASA, Hubble Space Telescope