You don’t have to be out late to go stargazing just now month as December is the month of the Winter Solstice and when we have our Shortest Day with under 7 hours of daylight. Although most of the bright stars are now missing from our sky, it is a good time to spot the Andromeda Galaxy, the closest spiral galaxy to our own galaxy, the Milky Way. Mars is a planet to watch because, on the morning of 8 December, it will disappear behind the Moon for about an hour during a rare lunar occultation (something that has not been visible from the British Isles since 1952). We also have the Geminids meteor shower peaking on the afternoon of 14 December. It may be possible to see up to 120 meteors an hour in the few hours before moonrise on either the 13 December or 14 December, so look out for them then.
This month the sun sets around 4:00 pm and the stars and the constellations start to become visible from about 6:00 pm. As with November, there is a great signpost in the form of the Square of Pegasus to help you find your way around the sky. It is a huge square made up of four stars of nearly equal brightness: Scheat, Alpheratz, Markab and Algenib and you should be able to see it high up in the south, above Jupiter in the early evening sky.
The top left star of the Square is Alpheratz. It is the brightest star in the constellation of Andromeda, which is marked by a line of three more stars running up and to the left of it. You can use this line to find the Andromeda Galaxy, one of the most famous features of the night sky and the nearest spiral galaxy to our own, the Milky Way. The best way to find it is to start Alpheratz and go a further two stars along the line, turn right and count another two faint stars along, and the Andromeda Galaxy (M31) will be close to the second faint star. If you are in a town, you’ll probably need a pair of binoculars to spot it, but if you’re in a dark place out in the country, you should be able to pick it out without using binoculars.
There will be more about Taurus and Orion next month, but for the moment, draw a line using the three stars in Orion's belt and follow it through Aldebaran and you’ll find the Pleiades star cluster (M45) a bit beyond it. This cluster is the brightest open constellation we can see in the night sky and is a grouping of stars, seven of which are visible to the naked eye, but the entire constellation has more than 1,400 stars. The name comes from the early Greeks who referred to the constellation as the Pleiades, or the Seven Sisters, who were daughters of Atlas and Pleione. These stars are mentioned three times in the Bible and are linked to origin stories for many American Indian tribes.
If you look north, you’ll see the same stars as you would in any other month, but their orientation varies from month to month. In December the familiar Plough asterism, which many people recognise, is moving from the north to the north-east. If you follow its two right-hand stars upward, veer a little bit to the right and you’ll find Polaris, the Pole Star. If you look high up over to the north-east, you can see Castor and Pollux, the two brightest stars in the Constellation of Gemini (the Twins), which represent the heads of The Twins. Meanwhile, low down in the North-West, you will find Vega, the brightest star in the Constellation of Lyra (the Lyre). It is the fifth-brightest star in the night sky, and the second-brightest star in the northern celestial hemisphere after Arcturus.
This month’s full Moon is called the Cold Moon because December is the first month of winter. Its Old English/Anglo-Saxon name is the Moon Before Yule, while another name for it is the Wolf Moon, however, this is more commonly used for January’s Full Moon.
Also, on the nights of 7-8 December and 8-9 December, the Moon will be very close to Mars. In fact, on the first of these two nights the Moon will pass in front of Mars and create a lunar occultation that will be visible from parts of the Americas, Europe and Northern Africa. You will need to be up early on 8 December to see it because it will begin at about 4:55 am when Mars disappears behind the Moon and will end at about 5:55 am when the Red Planet emerges from behind the Moon.
The last quarter Moon is on 16 December and the new Moon (no moon) is on 23 December so a couple of days later, on the evenings of 25 and 26 December, you should be able to pick out the thinnest of crescent moons sitting close to the southwest horizon as darkness falls. On 25 December, this crescent Moon will be near Mercury and Venus and on 26 December, it will be below and to the right of Saturn.
We have a first quarter Moon (a half moon) on 30 December and the day before, on 29 December, you will find it over in the southeast darkness falls when it will be sitting below and to the left of Jupiter.
Jupiter, the mighty gas giant, is now dimming as it continues to travel away from Earth. It has now moved from the brightest to the second brightest planet in the night sky, with Venus being the brightest. You will find it over in the southeast as darkness falls and it will stay above the horizon until it sets in the west at around midnight. If you look at it through binoculars or a telescope, you will see some tiny starry objects on either side of it. These are its brightest and largest moons. They are Io, Europa, Ganymede, and Callisto and are known as the Galilean moons. If you watch them on different nights, you will notice that they change position as they circle the mighty gas giant planet.
Saturn is below and well over to the right of Jupiter, sitting in the southern night sky as darkness falls and shining a lot less brightly. It sets in the southwest at around 8:00 pm but if you look at it through binoculars or a telescope before then, you be able to see its famous rings and its biggest moons. The largest moon, Titan, is enormous. In fact, it’s 40% more massive than the planet Mercury and 80% more massive than our own moon.
Not too far below and to the right of Jupiter, lies Neptune. However, this most distant planet will be very faint, so you will need a telescope to see it. It sets at about 11:30 pm.
You’ll find Uranus well over to the left of Jupiter and to the right of Aldebaran, the red eye of Taurus the Bull. It was at its closest to Earth on 9 November and is now moving away and becoming very dim as it does so. For this reason, it will be difficult to see, even with binoculars or a telescope.
Mars is visible all night long, appearing low down in the northeast sky as darkness falls. On 1 December, it will be at its closest to Earth since October 2020, reaching its maximum brightness then to become almost as bright as Jupiter.
However, the big event is on the morning of 8 December, when Mars reaches opposition at 4:24 am, just 16 minutes after the full Moon, so the Sun, the Earth, The Moon, and Mars will be almost exactly in line at that point in time. Shortly after, at about 4:55 am, the Moon will move right in front of Mars to create a rare lunar occultation and hide the Moon from view until about 5:55 am when the Red Planet will reappear (these times are approximate as the exact time will vary according to your location). This will be the first lunar occultation of Mars visible from the British Isles since 1952 and the next one won’t occur until 2052. If you decide to watch it, you'll easily spot it above the noticeable constellation of Orion the Hunter.
Finally, towards the end of the month, Venus begins another long reign as the Evening Star, appearing low in the southwest not long after sunset, before setting at around 5:30 pm. You’ll find Mercury to the upper left of Venus, but it will be very difficult to see as it will be 20 times fainter and lost in the Sun’s glare.
December is the month for viewing the shooting stars of the Geminids Meteor Shower. Unusually, they are not debris from a comet, but rather debris from an asteroid called Phaethon. The Geminids have become more plentiful in recent years and are considered by many to be the best meteor shower of the year. They are active from 4-17 December and during their peak, which this year is at about 1:00 pm on 14 December, it can be possible to see around 120 meteors per hour.
Their radiant point is in the north-east sky, in the Constellation of Gemini (The Twins) and close to Castor, one of its two bright stars. Although this is where they originate from, you’ll be able to see them at any point across the sky as they burn up in the upper atmosphere, some 60 miles (100 km) above Earth’s surface.
The best time to look for them is normally when the radiant point is at its highest in the sky, which will be at around 2:30 am. Unfortunately, a fairly bright waning gibbous Moon will rise at about 8:45 pm on December 13 to illuminate the sky and possibly drown out many of the shooting stars. It may be better to wait a day and watch for them on December 14 because the Moon will rise later, at just before 10:00 pm, and give you an additional hour without bright moonlight.
This year, the Winter Solstice will occur on 21 December at 9:47 pm and is the exact moment when the northern hemisphere is tilted furthest away from the Sun. However, many people refer to the Winter Solstice as the Shortest Day of the year, when the number of hours of daylight are at their minimum and the number of hours of night are at their maximum. On 21 December this year, our sunrise will be 8:55 am and our sunset will be 3:47 pm, giving us 6 hours and 52 minutes of daylight.