Comet Leonard’s flyby

Comet C/2021 A1 (Leonard) is a comet coming from far outside the Solar System. Discovered in the first days of 2021, from the initial calculations it was thought it would potentially become a relatively conspicuous object, reaching (and maybe exceeding) naked-eye visibility in late 2021 (closest approach to Earth on 12th December and perihelion on 3rd January). One curious fact about this comet is that it has a retrograde orbit, whose inclination to the ecliptic plane is so high that it appears to be orbiting the Sun “the other way around” compared to most solar system objects.

Comet brightness is always unpredictable because of their intrinsic nature, so nobody knew in advance how it would behave. Anyway, observing conditions would have been excellent for northern hemisphere observers in the wee morning hours until around December 10th. So, despite having to get up very early, no way I would miss out on this one!

What’s more, comet Leonard was expected to make two very close fly-bys with well-known deep-sky objects: the first with NGC 4631 (“Whale galaxy”) and NGC 4656 (“Hockey Stick Galaxy”) around 24th November, and globular cluster M3 in the morning of 3rd December. Two close encounters not to be missed!

Unfortunately I missed the first encounter with the two galaxies because of bad weather and personal engagements. However, imaging the close flyby with M3 more than made up for that. Anyway, I took all my photos from my backyard, in a heavily light polluted area.

I observed and imaged comet Leonard three times: on 1st December, 3rd December (for the close rendez-vous with M3), and finally on 7th December, when it was hardly visible from my location, which has an obstructed East view up to about 25 degrees elevation.

These days, comet Leonard is visible only from the southern hemisphere. While approaching perihelion, it has produced an outburst with a detail-rich tail more than 10 degrees long. It is beyond me why these breathtaking shows only occur when comets are not visible from the northern hemisphere. Go figure… Let’s hope for the next one anyway!