Caoimhín's Content

Today we are going to be continuing to look at the very end of this year We won’t look forward into next year just yet but we will look at some things other than the planets. There are of course plenty of planets up top be seen all month long, with Venus, Saturn, the Moon and Jupiter visible at sunset this weekend. Just a little later in the night Mars will rise as well. By the end of the month we’ll have Venus and Mars in the sky at the same time, this weekend however, that still won’t be the case, Venus will be setting before Mars comes up.

We are specifically taking a look at this weekend, the 13th and 14th of December, thanks to the Geminids Meteor shower which is peaking this weekend. The Geminids are technically peaking on the 14th, but it may be a better idea to start looking at sunset on the 13th. By comparing the maximum zenith hourly rate shown in the Stellarium program with the time adjusted rate, we should be getting 130 out of a theoretical maximum of 150, which is great rate of meteors. If we move forward another day, to the night of the 14th, that number goes down. The number is climbing as we push from the day of the 13th, past midnight, and into the early morning of the 14th. Although the peak is on the date of the 14th, this peak is very early on the 14th, giving us more meteors late on the 13th than we would get on the night of the 14th itself. The rate of meteors passing through the sky may get as high as 145 just on the 13th, but Stellarium shows another value just under this one, a local hourly rate of 50. Light pollution in a city like Cork will limit the faintest visible meteors to a magnitude of about 5.5, that is what brings this number down.

The light pollution in a city like cork certainly isn’t the worst possible. For example, we can see much of Orion like the Betelgeuse, Rigel and the stars of Orion’s Belt. We can just about see where Orion’s Sword would be but it is a dot, a single star rather than not a line of three stars in the sky, as it would be from the countryside. The Pleiades or the Seven Sisters, are also limited without being totally obscured. Well, not so much this weekend, with the Moon so close to them in the sky, we won’t really see much of the Seven Sisters at all with the nearly full Moon so close by in the sky. Changing the date to move the Moon even a little bit out of the way lets us see two, maybe three stars there, compared to the 7 or even 8 you can see under darker skies. This is light pollution, so if you’re hoping for 147 out of 150 from the city, you’re going to miss out on the fainter meteors, bringing that number closer to 50.

A local hourly rate of 50 is still great, better than many minor meteor showers under ideal conditions. I hope you remember some of my previous pieces where I gave out about newspapers and other media hyping up these kinds of smaller meteor showers. There are a few in December, a couple of which peaked earlier on the 8th of December. These are meteor showers that have already peaked, thankfully it seems that this time people didn’t mention them very much. However, if you saw anyone saying “Oh, there’s three or four meteor showers all happening together this month . . . “, the only big one really is the Geminids. As I said, from the city it’s not going to be as big, but 50 isn’t bad either. Even with the amount of light pollution we have in the city, the Geminids are a meteor shower that you can reasonably expect to see some members of at least.

By heading out to the countryside you’ll reduce the amount of light pollution, letting you see meteors as faint as magnitude 6.5 or fainter. This will bring the local hourly rate up, for example to 128 visible meteors per hour, out of 147 falling through the sky per hour, out of a maximum of 150 possible total at the peak. The Moon will be close to full and up for most of the night, which adds some light. On other dates, that will move the Moon out of the way, but of course it will also change where we are in relation to the peak of the meteor shower. If we push forward towards morning time on the 14th, with the Moon being a little bit past full, the Sun will start to rise before the Moon sets. The radiant of the Geminids will get lower in the sky, so the radiant of the Geminids will be behind a thicker layer of atmosphere, but of course the meteors can pop up anywhere in the sky, so that won’t matter too much. Closer to sunrise, the zenith hourly rate has started to go back down again, so that means we must have passed that absolute peak early on the morning of the 14th.

With the light of the Sun coming into the sky at sunrise, we’ve also got Mars quite high in the sky and Mercury just above he sunrise. In the countryside, these planets can be up with a local hourly rate there of 70, which could certainly make for a nice vista. On the morning of the 14th, after coming from the 13th, you’re likely to see more meteors from the Geminids than you would see in the middle of the night if you were in a city with as much light pollution as Cork City. The Geminids are coming up this weekend, they are a good meteor shower, much better from the countryside as all things but even if you’re in the city, the Geminids meteor shower is actually quite good. I have given out a lot in recent videos about how meteor showers can be overhyped or over exaggerated, but the Geminids are genuinely quite a good meteor shower to catch.

Moving back in time to sunset on the 13th once the glow of the Sun comes back into the sky, of course we are looking at quite early in the evening here, even at just 5:30 and the sky is already reasonably dark. There is still a little bit of a sunset glow, but I think given that it’s 5:30, saying that all we have left is the glow of sunset by 5:30 is more appropriate, it is quite early for the Sun to be going down. From out in the countryside, the Square of Pegasus and the Summer Triangle are clearly visible even this early. Taking a look at the constellations for the end of the month, you can definitely see the square of Pegasus there right above the south at just 6:30. This is of course still quite early in the night, once we move past midwinter the nights will start getting shorter again. We will also continue moving around the Sun, and so Pegasus will reach due South earlier and earlier. Instead of seeing it there at 6:30, it will reach there 6 and then at 5:30. However, the sunset will also get later and later, so it will it appear later, and further across the sky by the time it’s dark enough to be seen. It will appear to move thanks to our motion, but the sky will be changing not only because of our motion around the Sun, but when we see objects will also be changing because of the length of the day and the time of sunset and sunrise changing. All of this is going to make the sky appear to change quite fast.

Continuing later and still at just 9 o’clock, most of Aquila is already setting below the horizon, so part of the summer triangle is already setting by just 9 o’clock. We’re definitely not in summer, and I will keep saying that until we’re back into summer again with the triangle up all night long. We’ve got the Moon and Jupiter in Taurus, and we’ve got Andromeda pretty much due south. The Andromeda Galaxy isn’t exactly south or mor accurately towards the zenith from south, very high in the south. The Andromeda Galaxy isn’t exactly due south at 9:30, but it is very, very close, so a compass, I guess, is all you need to find Andromeda at 9:30 on this weekend on the 13th, because it will be in that easy to find position.

As the Moon was only just touching the horizon when the glow of sunrise came up on the morning of the 14th, that indicates that it is quite full, about 97.2% on the night of the 13th. We’ve got the Full Moon coming up on the 14th, still before midnight but on the 14th and we’re at 99.6%. The next day it’s down to 99.4, so that number is not going up. It does however go up as we move into the 15th from the 14th. As such it looks like the night of the 14th into the morning of the 15th is when we’ll get the fullest Moon that we’re going to see in Ireland. The Full Moon will reach the middle of the sky in the middle of the night. This puts it right above the south a little after midnight because of the way time works and the fact that we’re going off Greenwich Mean Time, even though we’re a little further over here in Ireland.

The Moon works differently to the Sun, but it does share something with the Sun. As we turn, the Moon arcs across the sky from east to west. It doesn’t exactly follow the ecliptic, of course the Moon follows our equator rather than the Sun’s equator, but the tilt of the Earth does still matter when it comes to how high the Moon is in the sky. If we look at the Full Moon at sunset, the Moon is rising very much in the northeast, and if we quickly push all the way through to morning time, we will see it setting very much in the northwest. This is similar to the Sun, of course the Sun on midwinter will rise very far to the south and set very far to the south. A Full Moon around midwinter will do the opposite, it’ll rise and set very far to the north, to the northeast and northwest for rising and setting. If we get a Full Moon in or around the solstice, then it can reach as far as possible to the northeast and northwest, but these things don’t always line up. We might get a New Moon on the solstice and miss the most extreme version of this event, because these cycles don’t line up perfectly. We’re not guaranteed to see a Full Moon rising or setting as far north as it possibly can, the Moon might not rise as far north or set as far north as it hypothetically could every single year. See the Moon appear in a different part of the sky due to the phase that it’s in. Regardless, the way our view of the Moon and the tilt of the Earth and the position of the Sun all interacts makes this year particularly extreme. The Moon this year is going to be at pretty much its furthest northeast and furthest northwest around the night of the solstice. This is, with the night of the Full Moon on the 14th and the Geminids meteor shower peaking on the 13th, not ideal. Thankfully, the Geminids meteor shower is worth it even with the light of the Full Moon.

I do hope the meteor shower will be good, I hope you get to see some of the Geminids meteors and I hope that you enjoyed this article. If you did, please do like it and you can subscribe to this website and my YouTube channel if you’d like to support more content from me. Thank you for reading and hopefully I’ll see you back here next time.