Why Is This Comet Bright Green? Comet C/2025 A6 (Lemmon), discovered earlier this year at Mount Lemmon, is becoming brighter as it moves closer to Earth and the Sun. It will pass nearest to Earth around October 21, and reach its closest point to the Sun on November 8. You may spot it in the evening sky later this month, especially near the bright star Arcturus. If predictions hold, it could become bright enough, around magnitude 3 to 4, to see with the naked eye from dark areas, or easily with b