Caoimhín's Content

Today we are going to take a look ahead to midwinter’s day, as it is coming up very soon now. We are on looking at the 21st of December for 2024, in other years the date of the winter solstice can vary to the 22nd or even 23rd of December. I will be talking from the perspective of Ireland here in the northern hemisphere, and as such I will refer to the December solstice as the winter solstice and midwinter, but this is the summer solstice for the southern hemisphere. Any information regarding the positions of the planets this year will apply to the southern hemisphere now, not for their wwinter solstice in June.

Beginning at midday on midwinter lets us see how incredibly low to the horizon the Sun is even at its highest point. Moving forward towards sunset we won’t have to move forward for long, because the sunset is so early in here Ireland at this time of the year. You can see as early as 4:30 the Sun is below the horizon, though sunset is only beginning. Venus will be emerging immediately, while Jupiter won’t quite be out yet. I won’t say that Venus is easily visible as early as 4:30, not in the city, but certainly by 4:45, and by then Jupiter should be visible as well. Jupiter is a little bit fainter than Venus, they are the two brightest objects that we only see at night-time, so not counting the Moon or the Sun, Venus and Jupiter the next two brightest objects in the sky in that order. Jupiter will look quite bright once the sky is fully dark, but with only the two brightest objects in the sky, it’s easy to see which is brighter. If we keep moving forward then we’ll get Saturn emerging, a little closer to Venus but definitely between it and Jupiter. We may see a couple of bright stars emerging before Saturn, but they will be emerge close together. Even though Saturn is quite bright and very easily visible to the naked eye, it’s still fainter than some of the bright stars.

Coming up to 6 o’clock and it will be almost perfectly dark by 6 o’clock, though we’re not quite there yet, there’s still a little bit of orange glow over on the Western horizon until about 6:20. Although the Sun will set a little after 4 o’clock, it is still civil twilight until 5. This is roughly the time when its still bright enough to not need streetlights. Nautical twilight continues until about 5:30, followed by astronomical twilight until about 6:20, then true night time begins. Astronomical twilight is dark enough for most purposes, though there might still be a faint glow over towards the West. I have been over the general features of the sky recently, but the square of Pegasus is still there nice and high to the South as the Sun goes down. The summer triangle, of course in midwinter it won’t be up for very long at all, it’s already quite close to the Western horizon. We’ll keep moving forward because of course we still have Mars to come into the sky, as well as Mercury in the morning. Going to go from sunset on midwinter through through the night puts us at sunrise really the following day. Although there isn’t much difference between the morning of the solstice and the morning after, there is a slight difference, and it is an auspicious sunrise, especially here in Ireland.

On midwinter we do just about get Mars and Venus into the sky at the same time, just barely. Practically it would be very difficult to see Venus and Mars at the same time, you’d need a very clear horizon both in the practically northeast and down in the southwest, so pretty much 180° of clear horizon. This is difficult to get anywhere, particularly in cities, and if you’re not in a city then you’re countryside and if you’re not in a desert or a very flat area like a salt flat, there’s probably going to be trees. If not there’ll be terrain, mountains and valleys, which can obscure your view. Getting up on a mountain, up on a high point will help you see a little more.

We have passed the opposition of Jupiter now, or nearly, so Jupiter should at least be very low to the horizon as the glow of the Sun starts to come up. This should leave us with three planets in the sky, I do think Mercury will show up before Jupiter goes under the horizon, but it would be even harder to see than Venus and Mars together. Perhaps if the horizon was completely flat we’d be able to pull it off, but here we are. As I said this is the morning after midwinter or after the night of midwinter, and Mercury is there as late as 7 o’clock in the morning. This is just at the end of astronomical twilight on the solstice, so there’s barely a trace of sunlight coming through from the sunrise. Really from about 5:30 in the afternoon till about 7 o’clock in the morning it’s dark, nighttime lasts quite a while in the middle of winter here in Ireland. From the Sun going under the horizon to coming over the horizon, we’re looking at really 4:00 in the afternoon to about 8:30 in the morning, so incredibly incredibly long nights in midwinter here in Ireland. Of course they are much longer in a more northerly latitudes, if you are above the Arctic Circle of course, night will last for several days, weeks or even months if you’re close enough to the north pole.

Looking at the actual morning of midwinter, the morning when midwinter begins, and can we can see definitely Mars, definitely the Moon and definitely Mercury. Jupiter is visible under the hypothetical situation where the horizon is completely flat and of course this is really hypothetical. We don’t have really anywhere that is perfectly smooth and flat all the way to the horizon on all sides here on Earth, barring the middle of the ocean on a still clear day. Hypothetically, in this sort of theoretical landscape you do get to see Jupiter and Mercury at the exact same time which is very cool. We can see here as well how Mercury is rising very close to the Southeast, where as Jupiter is setting practically in the Northwest. This shows the sort of tilt or skew of the expected passage of the ecliptic. If we were looking at one of the equinoxes, we’d see the ecliptic going from East to West, where as now we’re seeing the ecliptic at this very different angle, from southeast to northwest. It would be the opposite were we to look at this time, or the equivalent, in midsummer. If we looked at the sky at 7 o’clock in the morning in midsummer here and it would already be nice and bright, the Sun would have already risen. At the much earlier time of sunrise in midsummer, around 5 o’clock, the Sun would be rising far in the northwest.

We will move through the day, from sunrise on midwinter back to midday and then through to sunset again. If we take a closer look at sunrise, the atmosphere does make the Sun look like it’s risen a little bit before it actually has thanks to the refraction of light by the atmosphere. That can make the Sun look higher than it actually is. With no atmosphere, with the Sun almost resting on the horizon, turning the atmosphere back on would make the SUn appear to jump up a little, with much more significant clearance over the horizon. The atmosphere does make a difference, a thick atmosphere in particular does make the Sun appear to rise earlier and appear to set later. Even with that help, even with that extra couple of minutes, the days are still incredibly short for winter here in Ireland, particularly midwinter.

You will see that the Sun rises incredibly close to the southeast on the solstice, that’s the furthest South that the sunrise will occur all year. Once we get through to summer again the sunrise will happen much further to the northeast and on midsummer’s morning it is as northeasterly as it can get. This is the principle that allows a passage tomb like Brú na Bóinne, or Newgrange, here in Ireland, to keep track of the seasons. When the Sun rises on midwinter that’s the only time in the year that the Sun is far enough southeast to shine through the passage in the passage tomb. There’s a gap above the doorway into Newgrange, a “roofbox”, and the Sun will shine straight down the passage of that passage tomb only when the Sun rises at it’s most Southeasterly point, only on the winter solstice. That takes a lot of very careful measuring but it does also show an understanding that the Sun would only light it up on this particular date on midwinter. It would be a massive coincidence if that simply happened, given that they could have pointed it in any direction, the fact that it happens specifically on midwinter makes it interesting.

If you have a gap of some sort pointed at the roughly eastern horizon, the Sun will rise and shine through that gap, as long as the gap is big enough, on some morning of the year. The Sun goes incrementally along the horizon in its sunrise, and in its sunset as well. The Sun moves day-by-day, setting all the way down here in the Southwest for midwinter, it will set further and further north as we move past midwinter, and it will set directly in the West when we’re at the equinoxes. Technically, if you have anything that you can use to sort of make a viewport or viewfinder pointed along either the Western-ish horizon or the Eastern-ish horizon, there will be a date in the year when the Sun rises or sets and shines directly through that gap. However, for it to be one of the extremes, knowing that it’s only going to happen at that very extreme, that does show some understanding on the part of the prehistoric people, or Stone Age people, of Ireland. Newgrange was constructed a very long time ago.

Back at a little after sunset, Jupiter’s already well above the horizon, but just when it first appears you can see that it’s also far from due East. If we imagined the ecliptic coming down through Jupiter to the horizon, it would be practically northeast. Over the course of the night, the ecliptic line almost seems to rotate or twist across the sky. At sunset, the ecliptic stretches from way back in the northeast , across the sky and down in the southwest. If we lean back to look at the whole sky, with the invisible ecliptic visible, and go through the night, you’ll see how that chord across the sky moves. A chord is a line that goes across a circle, but not necessarily through the middle like the diameter. Moving through to midnight and it’s lining up directly East and directly West, and as we push forward to sunrise we can see that line slides along the horizon until it’s cutting through the southeast and northwest. Only in simulation is the ecliptic visible, so we get that kind of rolling of the ecliptic, the way it almost swishes across the sky. We get that every night but it is specifically at midwinter that we’ll get our sunrise for the furthest southeast at other times of the year you know, this swish sort of falls out of sync with the extreme end points, so where we see its endpoints, where we see the sunrise and sunset, will change.

That is a quick look ahead to really just the planets on midwinter’s night, and roughly how the sky will look as we move through the night. I hope you’re excited for the solstice and I hope you will stick around to see future videos coming out closer to the date of midwinter. I will look ahead to Christmas and New Year’s, the end of the year in particular, in upcoming pieces, if you’d like to make sure that you see those videos it helps if you subscribe to this website and my YouTube channel. You can also like this piece to support more pieces in the future and show that you liked it. Thank you for reading and hopefully I’ll see you back here next time.