What’s Up! December 2021

A monthly look at astronomical events in the sky and on Earth 

Compiled by Steve Sawyer and John Rowland


Yay, it’s nearly Christmas, time for mince pies, mulled wine and dodgy jumpers!

Plus it also gets dark nice and early and {hopefully with good weather)  they’ll be time over the Christmas break to get a bit of stargazing in.  Assuming everyone isn’t drinking the sherry!


So what’s on this month?

Well, we have comets, meteors, seven planets in a line and some good deep-sky objects (DSOs).  Not forgetting Santa of course as he whizzes around the globe on the 24th, hopeful not spoiling too many long exposures! 


Also, the long-awaited launch of the Webb Space telescope is scheduled: Engineering teams have completed additional testing confirming NASA’s James Webb Space Telescope is ready for flight, and launch preparations are resuming toward Webb’s target launch date of Wednesday, Dec. 22.  Fingers crossed!


December Objects

The Sun

The Sun continues to simmer gently, currently showing two small sunspot groups easily seen using the normal safe methods. Nothing dramatic but we’re definitely out of sunspot minimum now, so it’s always worth having a peak every now and again and/or going to Space Weather Prediction Center for up-to-date information.


The Moon

The New Moon is on 4th December at 0743 GMT. In fact, on this date, hardy folks at the Belgrano research station on Berkner Island in Antarctica would have seen a total solar eclipse lasting nearly two minutes if the station hadn’t been abandoned. We of course will see nothing, not even a partial.

On Monday the 6th December, a very thin (8%-lit) waxing Crescent Moon may be seen very low above the southwest horizon. If you have a clear view of the southwest horizon down to ground level then this might be possible to see it! (See the Crescent Moon Watch page for more details). The best days to observe the Moon’s cratered surface will be from the 7th to the 15th.


The Planets

You may be able to see seven planets shortly after sunset from the 28th of December to the 3rd of January. You’ll need a good flat horizon and no clouds! Have a look in the Sky at Night magazine for a full guide.



Evening planet, poorly positioned at the start of December. Near to Venus at the end of the month.



Low evening planet. Appears near Mercury at the end of December and a near waxing Crescent Moon on the 6th and 7th of  December.



A morning planet currently with the best time to see is being around 1 hour before sunrise. Mars can be seen with a thin crescent Moon nearby on the 31st of December.



Evening planet, unable to reach its highest altitude in darkness anymore. Moon close on 8th and 9th December.



Compromised by the evening twilight. Waxing crescent Moon nearby on 7th and 8th December.


Meteor Showers

This month it’s the turn of the Geminids (whose peak is on the 14th) but it might be better to observe them on the 12th or 13th late at night after moonset.  It’s possible to get up to 120  meteors per hour.



Comet C/2021 A1 Leonard may become a naked-eye comet this month.  It won’t be easy to see with the best time around 6:00 am.  Peak brightness is expected to occur on the 13th. Full details on how to find it on the EarthSky.org website.


Deep Sky Objects (DSOs)


This month is a great time to explore the winter Milky Way and take in some of the sights.

All of these are worth a look at but don’t forget to have a peek at the old favourites Orion and Pleiades especially if you’re lucky and have a crisp and clear night.


These are best seen during the first ten days of this month or after the 24th when the Moon isn’t around to lighten the background sky. The best targets remain those listed in the November What’s Up. However, there are scores of other objects to have a go at, mostly sprinkled along the Milky Way, which at this time of year arches right across the sky from ESE to WSW The two charts below show all DSOs of magnitude 6.0 or brighter, the first being the whole sky and the second a 100° span centred on the zenith. They are both taken from SkyViewCafe.com and correct for the 9th of the month. For a clickable list of Messier objects with images, use the Wikipedia link. To look up NGC objects, the best way is to enter NGC<object number> into Wikipedia.

Fig.1 Whole Sky 2021-12-09 Fig.2 Zenith Sky 2021-12-09


As it’s December we must include the Christmas Tree Cluster (NGC 2264)

You’ll find this up and left a bit of Betelgeuse. This star cluster is over 2200 light-years away and has a span of around 25 light-years. With a dark sight, this should be visible as a small smudge of light (mag +4.0) and contains around 80 stars arranged in a rough shape of a Christmas tree.

Fig.3 Christmas Tree Cluster (NGC 2264)


Man’s Space Activities


Spotting the International Space Station

The ISS is visible on many nights during December. Heavens Above web site gives all the details.  The link is preset to return the data for sightings from York. Use the left and right chevron buttons to change the date range. All times are BST.


General Space News

In addition to the James Webb Telescope launch mentioned above, there’s always something of interest going on in space. See the space.com website for the latest news. And for a detailed timetable of projected launches and other space-related activities, the Wikipedia website is an excellent place to start as it has links to each project/mission mentioned.


Answer to November 2021’s Challenge

The challenge was to identify a solar system object.

The person who built the illustrated telescope was William Lassell. He discovered Triton, Hyperion, Ariel and Umbriel. One of those – Umbriel – has been described as “the dusky melancholy sprite” (from Pope) and has an unusual crater – Wunda – whose walls enclose a bright ring that some have called an “eye”.


The reference to the star Sabik refers to the fact that Uranus and all its satellites have polar axes that are inclined to the plane of the solar system by 98° and whose “north” poles point roughly to the star Sabik in Ophiuchus. Congratulations to Mike Suttill who was the first to come up with the right answer. Neil Moss also got it right, so well done Neil too.

This Month’s Challenge – Graded Questions

To encourage wider audience participation, we have decided to add Graded Questions (i.e. from Beginners to Advanced levels) so everyone can have a go at answering a few questions. The winner(s) will be posted on the website (“Leave a Reply”) and also at the next YAS Meeting after the 15th.

Click here to take the December 2021 Challenge

We have double-checked all the answers for accuracy and correct spelling, so be careful, as only answers that are correct in every respect are deemed to be true.


Thanks for your interest, and we wish you clear skies and good viewing. Stay safe!

Steve Sawyer and  John Rowland!


3 thoughts on “What’s Up! December 2021

  1. Good guide as usual thanks for the effort again.
    Seven planets! if the weathers kind that will be worth looking out for, perhaps at BBF?
    Done the challenge this month, I will wait to find out how badly I have done but thought it was a good format. nice work.

  2. The Challenge/Quiz is now closed. Many thanks to all 20+ members who participated. The answers will be analysed by the quiz author (John R) and the results will be announced at the next YAS Meeting and next month’s What’s Up! issue, as usual.

  3. Top scorers will be announced at the on-line meeting on the 17th.
    Also, a file containing the right answers and explanations will be available.
    Maximum possible score was 13.
    21 people entered
    3 people scored 11
    3 people scored 9
    2 people scored 7
    4 people scored 6
    3 people scored 5
    2 people scored 4
    2 people scored 3
    1 person scored 2
    1 person scored 1

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