Caoimhín's Content

Today we will be looking ahead to the solstice and looking at sunlight visible at midnight. The attached video is an Irish language video, though English subtitles are provided as a convenience. We are looking ahead to the sky for summer, and during the summer Ireland uses Summer Time. Due to daylight savings, the time changes by an hour between winter and summer here in Ireland.

We are looking at the middle of the day, when the Sun is at its highest point, which is now at around 1:30, rather than 12:30. Also when we are looking at the middle of the night, the true middle of the night will be around 1:30 in the morning rather than 12:30. That is the physical midnight and physical midday, the real moment when the Full Moon or the Sun is at its highest point. The Moon is at its highest point at midnight only when the Moon is full, and we have to push ahead to next month to see the Full Moon. Unfortunately, hopping forward to the 11th of June, we only see the Moon at 99.7% full. The 11th is the date for the Full Moon, but in Ireland our Moon will be only almost full. The Moon isn’t completely full, and we’re not going to see the totally Full Moon, we aren’t going to see the Moon at 100% full here in Ireland in June. For this reason, the Moon won’t be exactly in the centre, straight in the middle of south, at exactly 1:30. We’re still a little before the Full Moon and for that reason the Moon will be directly in the south a little before 1:30, but not by much, just about 1:20. This is still of course a lot later than the midnight on the clock. If we are looking at that midnight , 00:00 on the clock, the Moon would still be to the east of south, not in the middle of the sky at all. Even at its highest the Moon is very low in the sky, compared to the midsummer Sun very high in the sky.

We’re not getting the Full Moon and the solstice on the same day, and that is useful. It’s a little bit easier to see the light of the Sun at midnight if there is no light from the Moon there as well. Taking a closer look at the Sun in Stellarium, times for sunset and sunrise are given, though there is no night written there at all. There is of course a period of time after sunset when the sunlight is still in the sky for a while, a couple of hours here in Ireland. This period of time is twilight. Although Sun is under the horizon, there is still light from the Sun coming into he sky. As long as that light is in the sky, it isn’t really night time. Looking ahead to sunset on the solstice, the 21st of June, we can almost catch Mercury as the Sun sets, in the glow of twilight. As we push later, it is clear that there is still sunlight creeping over the horizon straight in the north, even at physical midnight, at 1:30. If we remove the atmosphere, firstly there are a lot more stars visible, but there is also still a little light from the Sun. If we change the time of year, this light will vanish. It is a lot easier to directly compare midwinter to midsummer, jumping the whole way through the year It is a lot darker in at midnight in midwitner than it is in midsummer.

If go day by day instead, the sky will brighten for a time every month. That’s the Full Moon, bringing extra light into the sky. Between the Full Moons however, when the Moon is gone, the sky is darker each month as we move from summer to winter. That’s sort of problem with the Moon, the Moon puts the light of the Sun of back into the sky. The light of the Sun bounces from the Moon and for that reason the light of the Sun is in the sky, sunlight coming from the Moon. This makes it harder to tell that the sky is darkening, but if we jump from the middle of summer to the middle of winter you can see that the sky gets a lot darker. Midnight at midwinter is real night providing real darkness, but in the middle of summer midnight is not truly dark at all. The problem of extra light is a lot more serious in the countryside. Of course, it’s not really a serious serious problem. This extra light doesn’t happen outside of a couple of weeks of year, and it’s not artificial. This extra light is a natural thing, there is a little more light there during the summer at midnight. It’s not light pollution because it’s not something that is created by humans, it’s a natural thing.

In the middle of the countryside, out in a dark sky, without any light pollution, we’re still able to see the Milky Way. However, there is a little bit of light in the sky which we are able to see, and that will have an effect on how obvious the Milky Way is. If we push from the middle of summer to the middle of winter, the Milky Way is going to leave, or at least the brighter core region is. The Milky Way’s core will be on the wrong side of the Sun in midwinter, but that extra sunlight is going to leave the sky as well. To be honest, for the majority of places in Ireland, the sky is dark but not perfect. Most places in Ireland do have a dark sky, but not every part of Ireland has a truly dark, with no extra light. For the majority of places in Ireland there is at least some light pollution, even if it is far better than the sky in any city. There are a lot of places in Ireland where you can see the Milky Way for most of the year, but if you are looking in the middle of summer there may be too much light in the sky. It’s better to go out in maybe spring time, when the Milky Way is rising before the Sun, but close enough to midnight.

A couple of months ago the sky was very good for seeing the Milky Way. If we instead look at the sky in the middle of winter, the sky is completely dark. However if we look around at the Milky Way, there isn’t much of it visible. We’re looking at the sort of edge of the Milky Way in winter. Parts of it can be seen, but there’s almost a hole in parts. There are spaces and thin areas where very little of the glow is visible. We aren’t able to see the centre of the galaxy with all of light it provides. The north of the sky is at least very dark. If we go back to the middle of summer, then it is a lot brighter. There should be a “correct” amount of light pollution, for the glow of the summer twilight to obscure an otherwise visible Milky Way. Of course, the right amount of light pollution is nothing, no amount of light pollution is the right amount of light pollution. However, for the purpose of trying to show the way in which your view of the Milky Way changes from midsummer, a level of light pollution around Bortle 3 or 4. Bortle class 3 is certainly out in the countryside, it is a country sky. As such, you can see a little bit of the Milky Way. If we push back a couple of months, the sunlight is going to decrease.

Back in April maybe, with the Moon out of the sky, we can catch the impressive part of the Milky Way with all the darkness of night time. It is hard, but the Milky Way is there to be seen in April when the Moon is out of the way. We’ll push ahead to the middle of summer, back to the solstice. The solstice happens around the 21st or the 22nd day of June, it changes with the year, particularly with leap years. Furthermore, in the Stellarium simulation, when we are moving form one side of midnight to the other, the date changes and that interferes with the number of the day as well. We can still see the Milky Way in the middle of summer from a place with a dark enough sky. Even at just Bortle 3, which is fairly dark but still not truly dark. Even with a little bit of sunlight there, the glow is still visible.

It is almost sort of nice that we are able to see sunlight in the middle of the night. It is an odd and interesting thing that for just some of the year we’re able to see sunlight the whole time. For the whole year, the Earth is bent towards the North Star, tilted on its side by about 23.5 degrees. The Earth is tilted in the direction of this distant star and that doesn’t change for the whole year. What changes is whether or not we’re tilted towards the Sun. While the Earth is tilted this way, for part of the year we’re tilted in the direction of the Sun, but as we orbit the Sun from one side to the other, we end up tilted away from the Sun. The tilt doesn’t change, just what side of the Sun we’re on. When we reach the other side of our orbit, we’re still looking in the direction of that North Star, but we are tilted away from the Sun. A few months later we are back, tilted at the North Star and towards the Sun. While we are tilted towards the North Star and the Sun, then at night a little Sun creeps over the northern horizon.

That’s what’s going to happen in just a short time, we will see sunlight at midnight from Ireland, this is something we are able to do. There is no true night in the middle of summer here in Ireland. I think that this is an interesting thing. It is a strange thing that only happens here, as we are so far north. This doesn’t happen in countries closer to the equator, the change isn’t so big. Neither the length of the day nor the amount of light changes so much as it does here in Ireland.

If you enjoyed this piece, make sure that you like it. If you have an interest in this topic, then make sure to subscribe to this website and my YouTube channel. Thank you very much for reading this piece, and I’ll see you next time.