Giant comet found in outer solar system The discovery of the comet estimated to 100-200 kilometers across was made by Penn researchers following a comprehensive search of data from the Dark Energy Survey. Comet Bernardinelli-Bernstein is the most distant comet ever discovered and possibly the largest seen in modern times. Comet Bernardinelli-Bernstein (circled) is estimated to be about 1000 times more massive than a typical comet, making it arguably the largest comet discovered in modern times. It was discovered using images for the Dark Energy Survey (DES) by the 570-megapixel Dark Energy Camera (DECam) at Cerro Tololo Inter-American Observatory in Chile. These images show the comet in October 2017, when it was 25 au away, 83% of the distance to Neptune. (Image: Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA/P. Bernardinelli & G. Bernstein (Penn)/DESI Legacy Imaging Surveys)