The internet is bubbling with news stories about comet C/2014 UN271 (Bernardinelli-Bernstein). Current size estimates are that the comet is about 100-370 km across – much bigger than the previous size winner, Hale-Bopp in 1997 at 60km. There are big uncertainties at the moment, with C/2014 UN271 some 20 AU away. Those uncertainties will narrow, and we’ve plenty of time to do that it won’t reach perihelion until 2031.
Unfortunately its closest approach will be around 11 AU, with a currently estimated visual magnitude of about 14-15… so not a naked eye object and likely hard to see except for advanced amateurs.
Even so, it is so unusual to have an object of this size enter the outer solar system, it will be worth tracking this story over the next decade… who knows what C/2014 UN271 will tell us about the frigid wastes of the Oort cloud?
See more at: Astronomers Thrill at Giant Comet Flying into Our Solar System – Scientific American
Lee J. Russell, Author 