The discovery of Comet C/2014 UN271 Bernardinelli-Bernstein was announced just over a week ago, however the first images of the object were taken by the Dark Energy Survey back in 2014. It's unusually far from the sun and won't pass closer than 10.9 AU to the sun. Based on the brightness it could be 200km across, but we have a hard time knowing for sure due to the extreme distance.