What Is Comet Lemmon? Comet Lemmon, officially designated C/2025 A6 (Lemmon) and also known as Comet A6, is a large, long-period comet tracing a dramatic 1,350-year orbit around the sun. First discovered on January 3, 2025 by the Mount Lemmon Survey near Tucson, Arizona, the comet is now making a temporary and accessible appearance for…