Comet Leonard: A Gift at Christmastime

By: Bob King December 25, 2021 18

Multiple bright outbursts have made Comet Leonard stunning photographically and visible without optical aid from southern locations. More disruptions are likely in store as it approaches perihelion.

Comet Leonard on Dec. 24, 2021 — Braided flows of gas and dust stream from the head of Comet Leonard in a photo taken with an 8-inch telescope and QHY600 camera on December 24, 2021. Compare this image to the one below from two nights earlier.
*Michael Jäger and Lukas Demetz*

Comet Leonard (C/2021 A1), which appeared to stall out around magnitude 5 in early December, has become a surprise performer. Since transitioning to the evening sky, it’s undergone three successive bright outbursts — on December 15th, 20th, and 23rd — that catapulted it to naked-eye visibility at 3rd magnitude. After each flare-up, the comet had faded back to around 4th magnitude. Today, December 25th, it’s around 3½. More outbursts are likely as Comet Leonard speeds toward perihelion inside the orbit of Venus on January 3rd and suffers the full brunt of the Sun’s heat.

Comet Leonard from Namibia — In this deep exposure made on December 22, 2021, Comet Leonard displays a spectacular ion tail with kinks and multiple rays.
*Michael Jäger*

Jets in Comet Leonard nucleus — Like water from a rotary lawn sprinkler, dust jets blast from the comet’s false nucleus in this carefully processed image from December 23, 2021.
*Michael Jäger, Lukas Demetz* *and Qi Yang*

Each flare began with a dramatic brightening of the comet’s “false nucleus” — a bright starlike concentration within the coma. Amateur astronomer Piqui Diaz of Ezeiza, Argentina, noted a condensed but hazy coma on December 19.01 UT, but one night later, the comet’s appearance caught her completely off guard. Expecting to see a fuzzy glow, the coma instead looked like a bright “star” in her 90-mm refractor. The cause of each outburst is likely due to vaporization of fresh, dust-laden ice from solar heating as the comet dashes sunward.

Comet Leonard from Arizona — Comet Leonard shows off a pretty tail several degrees long on December 19, 2021, from Payson, Arizona. The comet’s altitude at the time was about 10°.
*Chris Schur*

Comet Leonard currently glows around magnitude 4 and hovers very low in the southwestern sky an hour to 75 minutes after sunset for North American skywatchers. Its altitude depends upon your latitude. From the southern U.S. the comet perches a reasonable 10° to 12° high at mid-twilight and may be faintly visible with the naked eye. But if you live in the northern half of the country, it practically scrapes the horizon with an altitude of just 3° to 5°. You’ll need transparent skies, an unobstructed horizon, and binoculars or a small telescope to see it.

Comet Leonard displays a bright, compact coma and short, east-pointing tail in this photo taken with a 200-mm lens on the evening of December 20, 2021, from near Duluth, Minnesota. The comet’s altitude at the time was just 3°.
*Bob King*

You’ll also need to know exactly where to look, and there are few bright stars to guide you there. But don’t despair. Using the planets to make triangles that included the comet at one apex, I spotted the fuzzy blob in binoculars from Duluth, Minnesota (latitude 47° north) on both December 20th and 24th. The camera did better, showing it more clearly than I could see with my eyes. Given the comet’s southern declination, Southern Hemisphere observers have the best view, with this celestial visitor standing 20° (and climbing) 90 minutes after sunset from mid-southern latitudes.

Comet Leonard finder map late December — This map plots the location of Comet Leonard (C/2021 A1) at 6:30 p.m. CST with respect to background stars on several evenings (00:30 Universal Time on the following date) in late December and early January. Stars are shown to magnitude 6. Use the bright planets and Fomalhaut to create a pattern to help you find the comet in an otherwise star-poor region of the night sky. Note that its apparent motion decreases rapidly as it crosses from Microscopium into Grus. Also, despite the apparent upward trend in the plotted positions, over this period the comet’s altitude actually decreases slightly for observers at mid-northern latitudes.
*Stellarium with additions by Bob King*

If you’re struggling to find the comet, take a photo of where it’s supposed to be. That’s what worked best for me. When it pops up on your display (replay) screen, you’ll know exactly where to point your telescope or binoculars.

Comet Leonard Dec. 23, 2021 nverted — In this inverted image, made with a 35-cm Meade Schmidt-Cassegrain telescope and STL11000M camera on December 23rd, delicate rays of ionized gas shoot “downwind” of Comet Leonard’s coma. “Comet Leonard could quite easily be seen with the naked eye when it was about 15° above the WSW horizon at the end of astronomical twilight,” writes John Drummond of Gisborne, New Zealand. “In 11 x 80 binocs the tail is quite magnificent, extending for about 2-3°.”
*John Drummond*

Comet Leonard Dec. 26, 2021 mosaic — Comet Leonard has experienced a number of tail disconnection events including one in progress in this mosaic image made on Dec. 26, 2021. The tail here measures 9° long.
*Michael Jäger and Lukas Demetz*

Comet Leonard’s ion tail has shown remarkable complexity that you can see for yourself in breathtaking images taken by Austrian astrophotographer Michael Jäger and others. Continuous changes in tail length, along with the appearance of streamers, kinks, and knots, show just how captivating and unpredictable comets can be. And all this from a kilometer-wide berg of dirty ice. Miracles of nature never cease.

Changes within Leonard's coma are apparent in these two images taken a day apart with a 150-mm refractor and Canon 500D camera from southwest of Tehran.
*Ali Ebrahimi Seraji*

Comments

Anthony Barreiro

December 25, 2021 at 5:55 pm

Here in San Francisco we've been having a spell of mostly cloudy skies and much needed rain. Thursday afternoon 23 December the sky cleared and the rain stopped. Venus was visible before sunset, so I walked up Bernal Hill to look for Comet Leonard. The clouds came back but the sky stayed mostly clear to the southwest. Starting about one hour after sunset and for about 20 minutes, the comet was very easy to see in 10x42 image stabilized binoculars, about 20 degrees left of Venus, 15 degrees lower left of Saturn, and conveniently placed between fifth-magnitude Alpha and Gamma Microscopii. The comet was brighter than these stars, I would guess around fourth magnitude, with a bright center and a nonstellar coma. I kept thinking I could see a hint of the tail pointing away from the Sun, with either averted vision or averted imagination. I tried repeatedly to see the comet naked eye, but no luck. Especially because of the unexpected break in the weather it was a real treat to see the comet.