The month of December sees the winter solstice, the shortest day of the year. One could argue that for this reason, December is one of the best months in the year for stargazing. Although it gets very cold at night, so wrapping up warm is essential. This year the winter solstice occurs on the 21st December with only 7 hours 29 mins of daylight.
The Geminids meteor shower peaks this month. It is usually a good shower but the Moon will make it hard to see them this year unless you stay up very late.
Sun and Moon
| Date | Sunrise (Irish Time) | Sunset (Irish Time) |
|---|---|---|
| 01/12/2021 | 08:17 | 16:10 |
| 15/12/2021 | 08:34 | 16:06 |
| 31/12/2021 | 08:40 | 16:16 |
| Moon Phase | Date |
|---|---|
| New Moon | 04/12/2021 |
| First quarter | 11/12/2021 |
| Full Moon | 19/12/2021 |
| Third Quarter | 27/12/2021 |
Planets
Mercury
Mercury is visible in the evening sky during December. The best time to see it will be in the last two weeks of the month. It will be well positioned on Christmas week appearing just below the planet Venus. You will need a location that has low clear south west horizon as Mercury will be very close to the ground.
Venus
December is a good month to spot Venus. It is low in the evening sky but still prominent in twilight. It will be unmistakable. Venus will be very bright in the southeast for about 2 hours after sunset at the start of the month and an hour after sunset at the end. On 6th December, a very thin crescent moon will be close to Venus. If you miss it on the 6th, it will be close on the 7th too.
Mars
Mars is in the morning sky during December and is poorly placed. Look for it 1 hour before sunrise low in the southeast. On 3rd December it will be close to the thin crescent moon and it will be close to the moon again on the morning of 31st December.
Jupiter
Jupiter remains in the sky in December but is getting lower in the sky as darkness falls. It will still be bright and unmissable early in the evening in the south. On the evening of 8th December, the moon will be close to Jupiter.
Saturn
Saturn is visible to the west of Jupiter, it will also be getting lower in the west as darkness is falling. For most of the month, Jupiter, Saturn and Venus will form a line in the early evening sky. On the evening of the 8th December, the Moon will be between Jupiter and Saturn.
Stars and Constellations
The above sky chart, from heavens-above.com is for 23:00 on 15/12/2021. You can click on the chart to open a new tab and bring you to Heavens Above. On this website you can generate a custom chart for the time and date you wish. The summer constellations are gone and the winter constellations are rising earlier each night.
To the northwest are Cepheus (the house), Cassiopeia (the queen), Andromeda and Pegasus (the flying horse). Andromeda is the location of the Andromeda galaxy which is the furthest object that can be seen with the naked eye. Although, you will need very dark skies to see it. Andromeda and the Milky Way galaxy are headed for a collision and will collide in an estimated 4.5 billion years.
In the south at this time of year, is the constellation of Pisces (the fish) and Aquarius (the water bearer). Mars is also in this area of the sky. Over in the east we have the winter constellations rising. You will see Taurus (the bull) which has a distinctive “V” shape and beside it the Pleiades or M45. Also visible will be Orion (the hunter). Most people are somewhat familiar with this constellation and will be able to pick out Orion’s belt. You may also be able to pick out the Orion nebula just below the Orion’s belt. This is a star forming region 1,344 lightyears away. Finally, low on the eastern horizon is Sirius in the constellation of Cannis Major (the dog). This is actually the brightest star in the sky, although we never see it at its best as it doesn’t rise very high from Ireland.
The Geminid Meteor Shower
The Geminid Meteor Shower peak happens in mid December each year. It is one of the best showers of the year but occurs in the winter when it can get very cold. This year the peak is expected to happen at 07:00am (Irish time) on the 14th December. This year the Moon is 78% illuminated which means it will wash out all but the brightest meteors. The Geminids are known to produce quite a few bright meteors so it is still well worth watching. The best time to watch is the nights of 13/14th and 14/15th December. If you want to get the best conditions possible, try setting your alarm for around 3am on the 14th as the Moon will have set.
To watch the Geminids, make yourself comfortable. A sun lounger or hammock is ideal. Also make sure you are warm, a sleeping bag can be very useful for this, as are hot drinks such as tea or hot chocolate! At this time of year you will need extra thermal layers, hats, gloves and scarves to make the experience enjoyable. You can look in any direction as the meteors will appear all of the sky.
Paul Smith 