Explanation: Not a comet, bright spiral galaxy Messier 51 is popularly known as the Whirlpool Galaxy. Just off the handle of the Big Dipper in northern skies, you can spot it at the upper left in this image from December 1st. The pretty 4 by 2.5 degree wide field of view does contain two comets though. Different in appearance, both comets are new visitors to the inner Solar System and are currently faint telescopic objects, highest above northern horizons in morning twilight. At lower left newly discovered comet NEOWISE (C/2016 U1) shows off a round fuzzy coma in the greenish light of diatomic carbon gas fluorescing in sunlight. Sunlight reflects from dust in the coma and stubby tail of comet Johnson (C/2015 V2) at upper right.
Tomorrow’s picture: pixels in space