Comet C/2021 A1 Leonard remains a beautiful object in the night sky, increasing cautious expectations among many comet chasers that it could become a dazzling naked-eye object later this month.
At the start of 2021, newly discovered comet C/2021 A1 Leonard was announced.
Excitingly it had the possibility of becoming bright during December 2021 and exceeding the threshold of naked-eye visibility in the run-up to Christmas.
However, as of 7 December, frustration continues for British comet-watchers wanting to see and photograph Comet C/Leonard.
After a couple of mornings of clear skies across almost everywhere, when many people had their first proper views of the comet, the cloud returned and prevented us from seeing Comet Leonard’s closest encounter with the beautiful globular cluster M3.
In other parts of the world blessed with clear skies, many astrophotographers took beautiful images of the comet closing in on and then passing the star cluster, and the contrast between the softly glowing green head of the comet and the salt grain-like stars of the cluster was striking.
This was captured beautifully by astrophotographer Joel Erwin (@JAErwin8), who posted his shot on Twitter.
Thought I’d join in all the fun! C2021 A1 (Leonard) racing past the globular star cluster Messier 3. Single 300 second shot. #Astrophotography #comet #CometLeonard #M3 #space #backyard @Optolong_filter @zwoasi @AstroBackyard @AstroCarone @DaydreamAstro @xRMMike pic.twitter.com/BcZ7EDewGH— Joel Erwin (@JAErwin8) December 3, 2021
Astrophotographers Terry Hancock and Tom Masterson captured this image of Comet A1 Leonard passing by globular cluster M3, and were surprised to find a meteor had sneaked into the frame!
The image was captured at the Grand Mesa Observatory in Colorado, USA in the early morning of 3 December 2021.
Now the comet has moved away from M3 and is passing the bright star Arcturus, but another named storm is now barrelling in towards us, bringing with it waves of thick cloud, rain and even snow, blocking the comet from view.
However, reports from observers elsewhere suggest that Comet A1 Leonard is healthy and is continuing to brighten.
There has even been a report from a very experienced comet observer based in Ireland that it – and its degree-long tail – is already visible to the naked eye, albeit under perfect conditions.
Comet A1 Leonard is now passing the bright star Arcturus, which means it is technically visible in both the evening and morning sky for observers at mid-UK latitudes.
Optimistic northern observers with flat and low horizons to their north west are now heading out to look for the comet after sunset, but the time it is visible in a reasonably dark sky before it sets is short.
The comet is a real ‘tree scraper’ and will remain so until we lose it from view after mid-month.
The best views of the comet are still to be had in the hours before dawn, when it is high in the sky for several hours before sunrise.
So, all we can do here in the UK is hope for a break in the weather.
Meanwhile, observers in other parts of the world are enjoying observing this comet through their telescopes and binoculars, seeing it brighten steadily as it falls towards the Sun.
Many comet watchers are now quietly optimistic that in a week or so, when the comet is at its best, it will be visible to the naked eye, and might even grow a pretty tail.
If it does we might yet see something very attractive in our twilight sky after sunset.
But as always it’s best not to get our hopes up – comets are notoriously unpredictable and anyone making a confident prediction is very unwise indeed.
We’ll see what happens next!
Comet Leonard: the story so far
Throughout November 2021 comet-watchers wanting to see and photograph Comet C/2021 A1 Leonard were very frustrated. The problem was the Moon.
At the end of November, just as the comet was predicted to be brightening enough to sneak it within the range of small telescopes and perhaps even binoculars, the full and then waning gibbous Moon was blazing in the same part of the sky as the comet, making it hard to see and washing out any detail in its tail and around its head.
That didn’t stop many people observing and photographing it of course.
Astrophotographer and Twitter user Paul Macklin (@MathCancer) captured a beautiful image of Comet Leonard on 28 November from his back garden in Bloomington, Indiana, United States, and posted it to his feed.
#CometLeonard (C/2021 A1) this morning (Nov 28th), showing 1 hour of movement against the stars at ~1450mm focal length.— Paul Macklin (@MathCancer) November 29, 2021
The tail is really taking shape! Possibly caught the emerging ion tail #Astrophotography #comet #C2021A1.
Full details: https://t.co/iTSSKRXt5O pic.twitter.com/VtcOYsg1RA
Tom Masterson and Terry Hancock collaborated to capture this image of Comet A1 Leonard from Grand Mesa Observatory in Colorado, USA.
In the image, which was captured on 25 November, the Whale Galaxy and Hockey Stick Galaxy can be seen in the background.
Everyone looking at this icy visitor from deep space couldn’t help wondering what the comet would have looked like if they could snap their fingers, turn off the Moon and see it in a dark sky…
On the morning of 2 December – after several days of cloud and rain here in the UK – we finally got our answer.
The comet is still not bright enough to see with the naked eye but it is now visible in binoculars, and has grown a small tail too, which appears a couple of degrees long in long exposure, guided photographs.
It is bright enough to photograph using a DSLR camera with even with short, unguided exposures, and images taken with motorised tracking mounts bring out the icy green hue of its head and show the tail well too.
Many observers were relieved to see the comet looking so healthy on the morning of 2 December, as you can see in my image below.
The relief was palpable. A few days ago reports were circulating on social media claiming that the comet had started to disintegrate.
These reports were based on a handful of images that appeared to show the comet’s head had developed a kind of hammerhead or anvil shape.
Why was this bad? Because when that has happened to comets in the past it has been an indicator that something bad was happening to them.
Last year several comets that had looked like they would become bright enough to see with the naked eye fizzled and fell apart after they developed these weird shapes, so there was much biting of fingernails while we waited for more detailed images to be taken.
Thankfully they showed that the comet appears healthy, and reports of its death – like most things on social media – were greatly exaggerated.
Where is Comet Leonard now?
So, Comet A1 Leonard is alive and well, and visible in the morning sky. Having passed beneath the stars of the Big Dipper it is now dropping down towards the bright star Arcturus, which it will pass between 6 and 7 December.
On the morning of 3 December the comet wafted past bright globular cluster M3, and no doubt many astrophotographers will have been out taking beautiful images of that close encounter.
Comet A1 Leonard will appear at its best around 12-14 December Dec, when it will be visible in both the morning and the evening sky too.
If your sky is clear after sunset on those nights Comet A1 Leonard will be found low in the sky, over to the right of the planet Venus, currently a bright ‘Evening Star’ shining in the twilight.
We’re still hopeful the comet will be a naked eye object then, and there’s even a chance that its brightness will be enhanced briefly by forward scattering of sunlight through the gas and dust in its tails.
If that happens, and if its fledgeling tail continues to grow, it might look very attractive in the dusk – we’ll just have to wait and see. Comets are famously unpredictable, but maybe Comet A1 Leonard has a surprise or two up its sleeve still…
How Comet Leonard came to prominence
Comet Leonard was discovered by astronomer Greg Leonard at the start of 2021, and many images taken in November already showed a decent coma and tail.
This had many speculating we could see enthusiasm and interest in Comet Leonard reach a peak in December, similar to what we saw in 2020 with Comet NEOWISE, which made headlines around the globe.
Indeed, as comet-chaser José J. Chambó recorded in an image captured by him (below) on 4 November 2021 from Mayhill, New Mexico, USA, Comet Leonard has certainly shown an increase in brightness over the past month or so, especially when compared to a previous image captured by José on 5 October (above).
“Since my previous image its look changed dramatically: in just two weeks its brightness has increased from magnitude 11.5 to 10,” says José of his 4 November shot.
“Its coma has increased in angular size from 4′ to 9′ having developed a strong outer halo of intense green colour, and its tail has grown from 5′ to 16′ in length.
“Everything continues signalling that the comet is very active and it keeps the expectation of being observable at naked eye in December.”
José then captured this image of Comet Leonard on 11 November 2021.
He said: “Since my image a week ago the comet has increased its brightness from magnitude 10 to 9.5 so it is already observable with small telescopes.
“Its coma has grown from 9′ to 11′ in angular size, while the tail has been extended from 16′ to 19′ in length with a narrower and sharp jet to antisunward direction.”
Keep up to date with José’s comet-chasing via his website Cometografía.
How to see Comet Leonard
Comet Leonard was positioned near mag. +4.3 Beta (β) Comae Berenices on 1 December, shining at mag. +9.3.
It’s expected to brighten to about seventh magnitude mid-month, making it an easy object to observe through binoculars.
An effect known as forward-scattering enhancement may boost its brightness so it becomes visible to the naked eye.
Forward-scattering enhancement may help A1 Leonard become visible to the naked eye between 10–16 December, peaking at mag. +4.0 around 13 December.
The best prospects of seeing Comet Leonard from the UK will be during the mornings of 1–13 December.
Its morning track is shown at the top of of this section, while just above we’ve shown how the comet moves relative to Venus in the evening sky.
Unless the comet brightens more than expected, the evening appearance will probably go unnoticed from the UK due to low altitude.