On the night of April 19, 1787, astronomer William Herschel noted an hours-long light as bright as the Orion Nebula emanating from the unlit, new moon. He had likely witnessed a "transient lunar phenomenon" (TLP) — a short-term change in the appearance of part of the lunar surface.
TLPs include brightening, reddish or violet blotches and foggy spots. In fact, some 3,000 TLPs have been documented over the past two millennia by people wielding telescopes, cameras or just plain good vision, said Anthony Cook, a research lecturer in physics at Aberystwyth University in the U.K.
