Astronomy Essentials

Comet Leonard in the evening sky

Comet C/2021 A1 (Leonard) from La Parguera, Lajas, PR by Raymond Negrón.

Comet Leonard is 2021’s best comet

Comet C/2021 A1 (Leonard) – 2021’s best and brightest comet – is now in the evening sky for Northern Hemisphere observers. We heard on December 15, and again around December 19-20, that the comet had brightened more than expected. Is it having outbursts as it nears its closest point to the sun in January?

New reports on December 20 also indicate its tail is slightly bigger. So keep watching the comet this week!

As always, dark skies are recommended for this diffuse object. And – although we’re not hearing reports of people viewing the comet with the unaided eye – Comet Leonard is still a good binocular comet. And it’s near Venus, the brightest planet! Comet Leonard swept closest to Earth on December 12, 2021, passing some 21 million miles (34 million km) away. Its exceptionally close pass of bright Venus (2.6 million miles, or 4.2 million km) happened on December 17-18.

Comet above a mountain.
View at EarthSky Community Photos. | John Ashley was in Arivaca, Arizona, last night when he caught Comet Leonard – 2021’s best comet – in the evening sky. John wrote: “Comet Leonard sets behind southern Arizona’s sacred Baboquivari Peak, illuminated by a 96% moon, during nautical twilight on December 16. Leonard showed a little bit of coma and tail through the atmospheric haze, to the camera at least. I couldn’t see the comet at all in real time, even searching through binoculars.” Thank you, John! Remember, you need a dark sky if you want to search for Comet Leonard.

Closest to Venus, closest to sun

Closest approach to Venus was at 9:08 p.m. ET on December 17 (02:08 UTC on December 18).

Comet Leonard will round the sun at perihelion on January 3, 2022, at a distance of about 56 million miles (0.6 AU, or 90 million km). Comets are typically brightest around perihelion, and the comet has been brightening and is still getting brighter. And, as recent activity shows, there’s always the possibility of brightness outbursts as Comet Leonard draws nearer and nearer the sun.

By the way, astronomer Greg Leonard discovered this comet as 2021 began, giving it its name. It’s been much-anticipated, and it’s turning out to be quite a fine object for viewing!

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Comet Leonard: Once in a lifetime

So Comet Leonard is the best comet we’ve had this year. Ordinary 7×35 or 10×50 binoculars from a discount store will surely show it to you (if your sky is dark). The comet might be glimpsed with the eye alone, the tricky thing will be to catch it at just the right time after sunset, not too early (when bright twilight will wash it out) and not too late (when it will have set). The free, online planetarium program Stellarium can provide a view from your location.

Nature provides us with sky events seen once in a lifetime, Comet Leonard is one of these. By that we mean that this comet takes tens of thousands of years to complete an orbit around the sun. As Bob King pointed out at in October 2021:

Orbital calculations revealed that the object had spent the last 35,000 years wending its way sunward after reaching aphelion at the chilling distance of around 3,500 AU (3,500 times the distance between our Earth and sun).


Heliocentric chart of solar system showing trajectory of Comet Leonard.
This perspective on Comet C/2021 A1 (Leonard) shows its trajectory through our solar system. North is up. You can see that its orbit will cause it to be initially visible from Earth’s Northern Hemisphere, and then from the Southern Hemisphere. Chart via The Sky Live.

Ultrafast comet

An amazing feature of this celestial visitor is that it’s an ultrafast comet. It’s traveling at 158,084 miles per hour (254,412 km/h or 70.67 km/second) relative to Earth.

But, despite its incredible speed through the vast space of our solar system, don’t expect to see this comet swoosh across the sky. Like planets, comets do move in front of the star background. But, to our eyes, they appear to move slowly due to the large distances involved. Is it possible to observe this comet’s motion.

Yes, if you’re a careful observer and willing to spend some time. The best way would be with a small telescope. You’d do it by taking a close look at the comet’s position relative to background stars. Then compare the telescopic view five or 10 minutes later to detect the comet’s motion. Despite its high speed, you’ll find that its distance from Earth – and the vast distances in our solar system – will cause the comet to appear as a very slow-moving object.

Location of Comet Leonard on December 31, 2021 just after sunset. Illustration by Eddie Irizarry / Stellarium


Location of Comet Leonard on January 1, 2022 just after sunset. Illustration by Eddie Irizarry / Stellarium


Location of Comet Leonard on January 3, 2022 (closest approach to the Sun). Facing Southwest just after sunset. Illustration by Eddie Irizarry / Stellarium

Comet Leonard photos in the evening sky

Submit your comet image to EarthSky

Comet C/2021 A1 (Leonard) on December 17, 2021 as seen from Rincon, Puerto Rico by Raymond Negron. Thank you Raymond!
A bright comet with a colorful sunset.
View at EarthSky Community Photos | Chris Zurita near Tucson, Arizona, USA, captured this sunset with Comet Leonard (C/2021 A1) on December 16, 2021, and wrote: “Been waiting for clear skies as we just had a storm roll in the last few days. Tracked the comet in the early mornings last week. Was waiting for when it would show up after sundown.” Thank you, Chris!
Twilight over a desert landscape, with one star appearing "fuzzy."
View at EarthSky Community Photos. | Eliot Herman in Tucson, Arizona, captured this evening view of Comet Leonard on December 15. It’s the fuzzy “star” in the upper right of the photo. Eliot wrote: “Comet Leonard C/2021 is an easy spot with optical help in the evening sky, but just outside my capability with the eye alone. This photo was captured in the fading Tucson light just above the haze layer. It might be a bit better by December 17, when it will be higher in the sky near Venus.” Thank you, Eliot! Will you see the comet after sunset tonight … near Venus? Eliot has a dark sky. You need one, too. Thank you, Eliot!

Comet Leonard photos in the morning sky

Dark sky, Comet Leonard is in the middle leaving a tail of green color.
View at EarthSky Community Photos. | C/2021 A1 (Leonard) on December 7, 2021, via Steven Bellavia in Southold, New York. Thank you, Steve! With the eye, in a dark sky, the comet will look more like a fuzzy “star,” perhaps with a tail extending to one side. Steve created this composite by stacking 45 60-second images (processed with Nebulosity 4). Thank you, Steve!
Time-exposure photo of a comet over an observatory.
View at EarthSky Community Photos. | John Ashley captured this time-lapse image of Comet Leonard before sunup yesterday. He wrote: “Early Saturday morning, Comet Leonard cruised past the square MMT Observatory … on top of Mount Hopkins, near Amado Arizona. Comet images were approximately 30-seconds apart in this interval photo, which also includes a meteor and vehicle headlights leaving the observatory.” Thank you, John!
Comet Leonard on the left and globular star cluster on the right.
View at EarthSky Community Photos. | On December 3, 2021, comet C/2021 A1 (Leonard) was near in the sky to the stunning globular star cluster Messier 3. Patrick Prokop in Savannah, Georgia, wrote: “Comet Leonard and M3. This is a composite of 30 x 2-minute exposures … ” Thank you, Patrick! See more Comet Leonard photos at EarthSky Community Photos.
Black and white capture of a dark sky. Comet Leonard and globular star cluster.
View at EarthSky Community Photos. | Chris Woodruff in Lockwood Valley, California, also captured the comet and M3 on December 3, 2021. Chris wrote: “Woke up this morning at around 4:30 a.m. PST in Valencia, California. I logged into my remote observatory in the Lockwood Valley and captured a set of 240-sec, 140-sec, and 60-sec images using my Radian 61 f/4.5 Imaging APO Telescope with an SBIG 8300c camera. Was very surprised to see how close these objects were (using your website as a guide). This is the first quick process using only the 240-sec images but will see if combining all of the images will give a bit more detail once I get a chance.” Beautiful, Chris! Thank you. See more Comet Leonard photos at EarthSky Community Photos.
Comet Leonard: Green comet with small, oblong white core surrounded by fuzzy green, and a nice tail.
View at EarthSky Community Photos. | Patrick Prokop in Savannah, Georgia, captured 24 2-minute exposures of Comet Leonard on November 27, 2021, around 5 a.m. to create this beautiful composite image. Thank you, Patrick! Submit your comet image to EarthSky.
Green fuzzy comet with long tail near two elongated smudges in a starfield.
View at EarthSky Community Photos. | Radu Anghel in Parjol, Romania, captured this view of Comet C/2021 A1 (Leonard) with a 4-inch telescope on November 25, 2021, and wrote: “Comet C/2021 A1 Leonard sliding silently with galaxies NGC 4631 and 4656 on the background on the morning of November 25.” Thank you, Radu!
Bright green fuzzy comet with tail crossing longish smudge with bulge in the center.
Raymond Negron took this spectacular image of Comet Leonard passing almost in front of the Whale Galaxy (NGC4631) from San German, Puerto Rico, on November 24, 2021. Thank you, Raymond!
Small fuzzy elongated green dot with long barely visible fuzzy tail in star field.
View at EarthSky Community Photos. | David Hoskin in Halifax, Nova Scotia, Canada, caught Comet Leonard on November 7, 2021, and wrote: “Comet Leonard (C/2021 A1) imaged this morning just before dawn. The comet is currently in Ursa Major and has an observed magnitude of 10.8, visible with a telescope aperture of 6″ or greater. The comet is predicted to brighten until 13 December, at which time it may be visible with binoculars.” Thank you, David!
Elongated fuzzy comet close to a distant galaxy with distinct spiral arms.
View at EarthSky Community Photos. | Eliot Herman in Mayhill, New Mexico, captured this photo of Comet Leonard and a spiral galaxy on October 30, 2021. He wrote: “Comet Leonard (C/2021 A1) is predicted to put on a nice show in a little more than a month. At present it is still faint at about magnitude 11, and on October 30 it had a very close conjunction with galaxy NGC 3897 in Ursa Major.” Thank you, Eliot!
Fuzzy green comet with short tail against distant star field.
Comet Leonard (C/2021 A1 Leonard) photographed on October 29, 2021, by Michael Jager (@komet123jager on Twitter) from Austria. Thank you, Michael!

Bottom line: Comet Leonard (C/2021 A1) – discovered on January 3, 2021 – is heading inward toward its January 3, 2022, perihelion. It still might become the brightest comet of 2021! Photos and charts here. Bookmark this post. We’ll be updating it.

December 20, 2021
Astronomy Essentials

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