Comet Leonard - December 2021

comet photo

(Source: Wikimedia Commons/Flickr/University of Hertfordshire Observatory)

If we are lucky, we will get a good view of a comet this month.  It is called C/2021 A1 Leonard, or just Comet Leonard for short.  It was discovered by astronomer Greg Leonard at the Mt Lemmon Observatory just north of Tucson.  The comet is on an estimated 80,000-year orbit, coming closest to Earth on Dec 12 and closest to the Sun on Jan 3.  However, after it swings around the Sun it will be on a trajectory that will eject it from the solar system, never to return.

During the month of December the comet will be passing through the constellations Canes Venatici, Boötes, Serpens, Ophiuchus, and Microscopium.  Prior to its close approach viewers in Tucson will be able to see it the east in the morning just before sunrise, and after close approach it will be visible in the west in the evening just after sunset.  Right around close approach it will be very near the Sun in our sky, so you will probably need binoculars to spot it barely above the horizon.

A comet's brightness is notoriously hard to predict.  It is possible it could have a big outburst making it easily visible to the naked eye, but it's also possible that it could stay below our naked-eye threshold or even disintegrate and disappear altogether.  We will just have to wait and see!