As we head into the festive period, gazing at the night sky may be far from your mind unless it is to look for signs of Father Christmas heading our way. However, December is often an exciting month for astronomers of all ages and abilities, and this month looks set to be no different.
Of course, we will kick off proceedings with the phases of the Moon for this month. I do not think that, at this point in the year, I need to reiterate why it is so important that we all take note of, at the very least, the date of the full moon.
| New Moon | First Quarter | Full Moon | Third Quarter | New Moon |
| December 1st | December 8th | December 15th | December 22nd | December 30th |
Did you notice the occurrence of two new moons this month? I am certain that you will have heard of a Blue Moon, which is when we see two full moons in one calendar month. When we experience two new moons in one calendar month, we call it a Black Moon. These take place approximately every 29 months, so we will not get to witness this particular type of Black Moon again for more than two years.
There is a second type of Black Moon, which is determined not by the calendar month but by the seasons. Due to each season being approximately three months long, we can usually expect to see three new moons within each season. However, when a season sees four new moons rather than three, the third of these is also called a Black Moon. These take a little longer to come around, with roughly 32-33 months between each one. The next seasonal Black Moon is not due until next summer.
There is one obvious disadvantage to a Black Moon – you cannot see it! This does not make it any less exciting for astronomers, though, as the darker skies brought about by the Black Moon make it easier to view objects that might otherwise be too faint to see.
- Diagram of the Winter and Summer Solstice. From Encyclopædia Britannica, Inc. Source
Winter Solstice will take place on December 21st, the day of the Winter Ball. This is the moment when the North Pole is tilted as far from the Sun as it can be, but we commonly refer to the entire day when we speak about the Winter Solstice, which also marks the beginning of astronomical winter.
Meteorological seasons are based on the temperature cycle for the year, with each season beginning on the first day of the first calendar month in each season i.e. meteorological winter begins on December 1st and meteorological spring begins on March 1st. Astronomical seasons are based on Earth’s position relative to the Sun, with each season marked by a solstice or an equinox. If you find yourself ready for the start of Autumn as soon as September rolls around, but your friend is adamant that Autumn does not begin until September 22nd, you are both right! You are just measuring your seasons in two different ways.
I hope that you all have a wonderful festive season this year, filled with love and laughter, and that you spread kindness to one another.
Alex J. Halsey
