December 2024 Stargazing Guide

Greetings junior scientists, scientists and citizens of the great big weird, wild and wonderful world in which we live. As always I'm your humble science communicator the great Orbax coming to you from the Department of Physics here at the University of Guelph and I'd like to welcome you to our December 2024 Star Gazing Guide!

Well here we are. December. If you've been trying to look up for the last few months you may have noticed a seemingly omnipresent ceiling of clouds hiding our view of the cosmos from us. December can be cold, but also crisp! And we're hoping for clear skies... but what should we look for this month?

We get back to some familiar constellations, seek out the moons of a distant world, talk about the winter solstice and desperately try to catch a shooting star or two.

All this and more when we just take some time... to look up.

We've been talking so much lately about comets, asteroids and the planets that I feel like we've overlooked the stars themselves. Well this month we see the return of some familiar constellations. Look to the East just after sunset to catch the familiar asterism of Orion's Belt rising over the horizon. Going straight up from Orion you'll see Jupiter and going about that distance again you'll spot a trio of nicely visible constellations. The first is Perseus the mythical hero that slew the Gorgon Medusa. Moving a little up and South you'll see Triangulum which is... well... i's a long narrow triangle.

And while it seems pretty simple, Triangulum is actually one of the original constellations cataloged by Ptolemy in the 2nd century AD, more than 2,000 years ago!

Finally just below Triangulum is Aries the Ram.

Aries is one of the zodiacal constellations that we discussed in last month's star gazing guide and yep, you guessed it, it sits right on the ecliptic.

Lots of planetary action this month.

Venus remains in the southwest sky for a few hours post sunset brighter than any other star or planet.

Saturn will also be visible in the evening near Venus, setting around 10 p.m. by the month's end and following the path of Venus along the ecliptic.

Since summertime we've noticed Jupiter gaining prominence in our sky going from a morning planet to most recently rising a few hours after sunset.

Jupiter will be its closest to Earth on December 6th and at Opposition on December 7th.

This simply means that the Sun will be on one side of the Earth and Jupiter will be on the exact opposite side resulting in the most reflected light that it can receive and the brightest that Jupiter will be all year.

Jupiter will actually be the fourth brightest object in our sky right behind the Sun, the Moon and Venus.

On the night of the 7th Jupiter rises in the east at sunset and sets in the west at sunrise. Now while Jupiter will be the brightest all year that night the Galilean moons of Jupiter will also be at their brightest.

Ganymede, the largest of Jupiter's moons, is bigger than the planet Mercury. And Callisto, the second largest of Jupiter's moons, is a little bit smaller than Mercury.

Both of these moons are also potentially visible to the unaided eye so here's a fun trick for spotting them. First, find Jupiter. Now set yourself up in such a way that you can block your view of Jupiter with something thin like a telephone pole. With the light from Jupiter blocked you should be able to see two tiny little star-like points just beside where Jupiter should be. That's Ganymede and Callisto!

For a closer inspection a pair of binoculars or a small telescope works great. For which nights are the best and which side of that pole you should be looking at check out the link in the video description below.

Our full moon this month occurs just after 4:00 a.m. on Sunday December 15th. Settlers refer to the onset of winter by calling this full moon the Cold Moon but many of the First Nations refer to the high altitudes and long nights accompanied by the moon with their winter solstice names. The Ojibwe refer to the full moons around the winter solstice as "Spirit Moons”, and the Mi'kmaw of the East coast refer to this December full moon as the Winter Time Moon Kesikewiku's, or the Great Moon or the Chief Moon Kjiku’s.

The first day of winter is December 21st and is defined by the winter solstice.

What's a solstice?

Well, we say that the Earth has an axis about which it rotates. It's like an imaginary line that joins the North and the South poles. Every full rotation about this axis is one full day and that takes 24 hours.

Now this axis isn't perfectly perpendicular to the plane of our orbit around the sun it's actually tipped at 23.5°. The summer solstice back in June marks the day when the North Pole is tipped closest towards the Sun. The winter solstice on December 21st, however, marks the day that the North Pole is tipped furthest away from the Sun and it is then that the Northern Hemisphere will experience the least amount of daylight hours that it gets in a single day all year.

As a matter of fact, the Arctic Circle receives no daylight at all! Just 24 hours of darkness.

December 21st is often referred to as the shortest day of the year which is kind of confusing since a day always has 24 hours. In reality we just experience the least amount of daylight hours on the solstice. From this point on, as we head towards Summer, the daylight hours will increase in length while the nighttime hours will get shorter.

One last thing! This month we've got two meteor showers taking place. The Geminids are considered to be one of the best meteor showers of the year with over 120 multicolor shooting stars per hour and named for the constellation Gemini.

Unfortunately this year it peaks on the night of the 13th and the morning of the 14th, meaning that the light of the nearly full Moon will block all but the brightest of meteors.

Later in the month are the Ursids. Unfortunately the waning gibbous Moon, which rises around midnight that night, will interfere with our observations of that meteor shower as well.

But if you've learned anything about astronomy so far junior scientists you've learned that there's always hope!

Good luck.

Well there we have it junior scientists. For many of you December is a time to take a break from your studies. With the early sunrise and the late sunset we'll have over 15 hours of dark skies to gaze into the infinite, seek the unseeable and take some time... to look up.

See you next month junior scientists and don't forget to have a science-tastic day!

Special thanks to Royal City Science's own planetary geochemist Dr Glynis Perrett for her help preparing our star gazing guide and the Royal Astronomical Society of Canada.