All information presented here is taken from my book Nightscenes 2021 (pt2)

Click on the monthly image to get a larger high resolution view of the night sky set for 53° N (Horncastle, England) but is usable for the UK and Eire.  All charts are set for the 1st of the month at 22:00 GMT (10pm) and can be used on the other dates and times shown in each corner of the chart.

December 2021

Solar System quick summary

Some charts & images in the text can also be clicked to give a larger view.

Venus remains an evening twilight object and almost catches up with Jupiter & Saturn before falling back into the bright evening twilight. At the end of the month Mercury makes an appearance next to Venus in the last few days of 2021. Neptune and Uranus are evening targets along with Ceres, whilst we may have a ‘bright’ comet C2021 Leonard A1 skirting the western horizon and for a while in the morning sky too. Mars is a morning planet. The Sigma Hydrids, Gemind and Ursid Meteor showers peak on the 9th, 14th and 22nd.

Main events

It is now all happening in the evening sky with respect to several of the main bright planets. Jupiter and Saturn lie to the left of Venus the latter of which has dominated the evening twilight for many months and it is at greatest illuminated extent on December 4th. A couple of evenings later, look at around 5pm for the three planets when they are joined by the moon (above).

It lies to the lower right of Venus on the 6th, forms a triangle with Venus and Saturn on the 7th, forms another triangle with Saturn and Jupiter the next evening then completes the sequence by lying to the lower left of Jupiter on the 9th. The chart above shows the Moon twice normal size.

Venus is now beginning to lose the race with the Sun and its motion along the ecliptic. Venus seems to slowly get closer to Saturn and they are at their closest around the 17th/18th after which Venus begins to draw away as it slides back towards the Sun. As it happens, on those two evenings Comet C/2021 Leonard A1 passes below Venus skirting the horizon. Venus, the comet and Jupiter & Saturn all lie now in the S to SW evening twilight so look around 50 minutes after sunset and use binoculars in the hope the comet is bright enough and hasn’t ‘fizzled’ out! Meanwhile Jupiter lies close to Mu Cap on the 5th then lies north of Iota Aqr on the 25th/26th as a bonus.

Comet c.2021 Leonard A1 chart 1 for the morningh sky before dawn

Chart 2, again morning sky as twilight begins

Chart 3: Evening sky with the Comet low down skirting the evening twilight horizon.

Switching to the morning sky, Mars slowly climbs higher in the morning twilight and during early December it passes through Libra into Scorpius then into Ophiuchus. We pick it up on our chart here from December 15th to 31st ~ an hour before sunrise. Mars lies between Graffias Scorpii and Dschubba on the 18th. The next morning it lies very close to the wide, naked eye,  double star Omega being closest to 2 for  fine view in binoculars or telescope.

Mars continues on, and on the mornings of the 25th & 26th it passes just over 4 ½ degrees north of Alpha Scorpii, Antares, often called the ‘Rival of Mars’. This is due to both being a ruddy/orange colour so take the opportunity to compare them! Antares is mag 1 whilst Mars is a little fainter at mag 1.5 so can you tell the difference? On the last morning of 2021, the crescent moon will form a triangle with Mars and Antares for a great end to the morning events of the year.

The moon is always involved in many of our events and on the evenings of December 16th & 17th it lies in Taurus not far from M45 and the Hyades clusters. Dwarf planet Ceres also lies in this area and moves away from the Hyades as shown here on the chart set for 6pm. On the 16th the moon lies to the lower right of M45, the Pleiades star cluster with Ceres not too far from it too. But Ceres is magnitude 7.5 and the moon is a gibbous phase so quite bright.

The next evening the moon lies to the upper left of Aldebaran and the Hyades but is also just to the right of Tau Taurii. Later in the evening around 9pm onwards the moon closes the gap to the star and for parts of the UK it occults Tau. The chart below shows disappearance and reappearance but this will vary depending on your location as northern areas will see a graze or a near miss. What makes it particularly interesting is Tau (mag 4.3) is a double star and the fainter companion (mag 7) is occulted first. So if it is clear then keep a look out from 9pm and see how long the occultation(s) last for your location.

Mention should be made of the three meteor showers this month. The Geminids peak on the 14th are best seen in the morning before sunrise and after moonset to get the best of them. The Ursids peak on the 22nd just a few days after full moon but as they are circumpolar you may get a few in the evening before moonrise. However we also feature a minor shower, the Sigma Hydrids which peak on the 9th. The moon is in the early evening sky so once it has set then it bodes well as the radiant in Hydra steadily rises and becomes better placed to view. The ZHR is low at 7 but as conditions are almost ideal then if you’ve never spotted any from this shower before, now may be a good time to do so. Don’t be confused with any early Geminids though! All three radiant positions are shown on the monthly all sky chart.

Finally we return to Venus in the evening twilight in the last few days of the year as it is joined by Mercury in a  last flourish for 2021. Venus is sliding into the bright evening twilight as we view at ~ 40 minutes after sunset from December 25th to Jan 1st on the chart. As it does so, Mercury climbs up into the twilight to join it. Venus is naturally the brightest of them at mag -4.2 whilst Mercury is mag -0.7 on January 1st 2022 when Mercury and Venus will be level to each other in the sky.

During this last week of the year you can also view all the major planets in the solar system during the course of a night so why not do a planetary marathon, as long as you don’t freeze! A great way to finish 2021 and lead into 2022!

Also look out for the following:

10th  The Moon forms a line with Psi Aquarii and Neptune (evening)

14th  Moon lies to right of Uranus (evening)

18th  Nearly Full Moon lies between the horns of Taurus (evening)

20th  Moon lies close to Mebsuta, Epsilon Geminorum (morning) /

 Moon forms triangle with Castor and Pollux (evening)

24th  Moon lies above Regulus and occults Eta Leonis (morning)

26th  Moon lies close to Nu Virginis (morning)

27th  Last Quarter Moon forms triangle with Zaniah and Porrima (morning)

28th  Moon lies above Spica (morning)

Clear skies, happy sky watching and stay safe!


Webmaster  © Paul L Money 2021

The UK & Ireland Night Sky for 2021

The Winter Solstice occurs on December 21st at 15:59 GMT. Winter officially begins in the Northern Hemisphere whilst Summer begins in the Southern Hemisphere.