Largest known comet has been traveling for millions of years NOIRLab/NSF/AURA/J. da Silva (Sp J. da Silva/NOIRLab/NSF/AURA This illustration shows Comet Bernardinelli-Bernstein as it might look in the outer solar system. By Ashley Strickland, CNN Astronomers have discovered the largest known comet, and it’s about a thousand times more massive than others. Comet Bernardinelli-Bernstein, so named because it was found by University of Pennsylvania department of physics and astronomy graduate student Pedro Bernardinelli and Professor Gary Bernstein, is between 62 to 124 miles (100 to 200 kilometers) across. The team announced the discovery in June. This unusual comet will make its