Caoimhín's Content

Today we are going to take a quick look ahead to the month of September.

We’ll start with the sunset in early September. Early in September the sky won’t be too different from what we’re seeing in August, but it will be starting to get darker a little bit earlier once we’re a little into September. The September equinox will be coming up close to the end of the month. Even by 9:30, although there’s still a little glow of sunset, the sky is reasonably dark. In the east Saturn’s already into the sky as it is coming up to opposition, again closer to the end of the month. Saturn will be with us all night long and it will be at its brightest, directly opposite the Sun on the other side of the Earth. Down in the south is Sagittarius, the Moon will be passing in front of it early in the month. Moving forward another couple of nights and the Moon crosses the sky, leaving Sagittarius and Scorpius visible. The summer triangle is also up nice, and early already directly in the south. This is a sign that we’re moving out of summer, because the summer triangle is already up so high as soon as the sky gets dark, that’s an indication that it will be out of the sky or at least partly out of the sky before the Sun rises.

Moving ahead towards sunrise, Altair, one of the stars in the summer triangle, will be the first to bip out of view. It starts by falling just behind the trees and buildings here, but it will be going under the horizon proper soon after. This will happen a little after 5 o’clock, which is certainly before the Sun rises in the east. It is close to sunrise, with Orion already up along with Sirius. Also up by then are the Pleiades, along with the planets Jupiter and Venus. All of these things are now up in darkness, and the sky will still be dark even a bit after 5. It’s still dark because we are, as I mentioned, getting closer to the equinox. We’ll keep pushing forward, the Sun will start to rise and so will Mercury. Mercury is leaving the morning sky as we get a little bit later into September, certainly once we’re through to the 9th. Coming back a little to the 7th, Mercury will already be out of the sky in the morning for those of us here in Ireland. You can see Mercury for a little bit longer if you are in a different location on Earth, a bit closer to the equator. Venus and Jupiter are continuing to get further apart. Venus is still with us, but it will be leaving the morning sky in the near future.

We’ll move back in time on the 7th, from sunrise back towards sunset, so we can see the planets there disappearing. Jupiter is only coming up at about 2 o’clock in the morning, so it’s still very much a morning time planet. Most of the planets will only be visible for us in the morning for this month. Saturn is up pretty much all night already, but it will actually reach opposition closer to the end of the month, around the equinox. We’re just coming back to sunset, now back to the 6th due to crossing midnight. We’ll hop forward to sunset on the 7th in order to catch the lunar eclipse. Just at sunset on the 7th, as the Moon is rising in the east, we’ll take a quick closer look at the Moon. From here in Ireland, we do get a reasonable portion of the Moon eclipsed, but it will get less and less as the Moon rises. You can take a look back at a previous piece where I talked about the eclipses in September. We have a total lunar eclipse, only partly visible from Ireland but we will also have a partial solar eclipse visible down south in places like New Zealand.

We’ll move forward now, closer to the middle of the month, around the 14th. The Moon is past full, so it won’t be up early in the evening. As the Sun is going down, Saturn’s already there. Scorpius with Antares will be setting very soon after sunset, at just about 9:15 and again it’s already dark. There’s not as much glow of sunset even though we’re looking at the sky about 15 minutes earlier than we were at the beginning of the month at the beginning of the video. Again, things are going to get darker earlier as we’re coming up to the equinox. Very soon, before the end of September, the nights will be getting longer than the days again. We’ll keep pushing forward and we can see that the summer triangle is already well past south before we come to the middle of the night. Turning around to the east here we can see the Moon is just coming up much later now that we’re so much past full. Above Saturn, the square of Pegasus is now up nice and high and we can see bits of Andromeda just after it as well. We’re starting to see different constellations as we move back towards winter time, we’re starting to lose those constellations that were so prominent during the summer.

We’ll keep pushing forward, coming back around to 2 o’clock, and Jupiter comes back into the sky. We’re through to the 15th, but we’ll move back a couple of days due to an occultation of the Pleiades that’s coming up on the 12th. Early in the morning of the 12th is probably not going to do it, as it looks like the Moon is too far behind. We’ll take a closer look at the Pleiades and if we move forward, we’ll see that they get closer, but we end up moving into daytime. What we need to do is move through to the 13th and come backwards in time. We need to come all the way back to moonrise. This is something that we will also just about catch as the Moon is coming up and with the extinction of the atmospheres, because these things are so low down in the sky, the Pleiades are going to be a little bit harder to see. This is particularly true from the city, and of course the light of the Moon is going to make the Pleiades a little bit trickier to see as well. All the same, as the Moon rises it moves in front of the Pleiades, it’s passing in front of the Seven Sisters pretty much perfectly.

Now unfortunately, we’re not getting a fantastic view from Ireland. Taking away the atmosphere to get a slightly better view will let us see the stars themselves a bit easier. For this occultation, we in Ireland won’t quite see the occultation just as it’s starting, because the Moon will still be under the horizon. The Moon will already blocking out one of the Seven Sisters by the time it becomes visible to us here. Then it will move across the Pleiades and out the other side in the space of just an hour or so. These occultations, really anything to do with the Moon, are going to be fairly quick. The Moon will be moving quite quickly across our sky so the event, the thing that we’re looking for, it’s not going to last for very long. I’ll save further investigation for another time, we won’t just yet figure out the best place to see this occultation, but it is visible as the Moon is rising until a little bit before midnight. It will start, not just as the Sun is setting, but at around 10:30. This is a little bit after sunset, the Moon is a little bit after full so that’s when it’s going to rise, already starting to occult the Pleiades on the 12th. This is the night of the 12th before we get to midnight. By the time we’re through to the 13th, the Moon will already be after moving past and the occultation will be over by the time we cross midnight into the 13th.

As I mentioned, a lot of the interesting things are coming up a little bit closer to the end of the month, such as the opposition of Saturn, the opposition of Neptune and the equinox. Let’s very quickly take a look at Saturn as if we were viewing it from the city. We’ll move back earlier in the night because we can, Saturn’s already nice and above the horizon here just a little bit past 10. We’re seeing it illuminated 100% and its distance from the Earth is just about 8.5 AU. If we move around a couple of days, that number will change. It seems like 8.547 AU is about the closest it’s going to get. Of course, the AUs are rounded a little bit, they’re a much bigger measurement than the kilometers, so it ends up being a little bit less precise. There’s not as many significant digits, not as many as you would see in the kilometers measurement. This helps us to make sure we are at opposition on the 21st. Taking a closer look at Saturn, the rings are almost edge on. They’re still there, but very narrow and difficult to see. If we move through time a little bit, the tilt of Saturn changes, and as the tilt of Saturn changes, the angle at which we’re seeing the rings will change as well. Moving off into the future, they get thinner and become more or less invisible as we get through to November. Coming back a little bit closer to today, they’re still very narrow, they’re still almost edge on, but we are seeing them a little bit better.

We can see several of Saturn’s moons as well, though of course you do need a pretty big telescope to see them, Titan being an exception. Titan is a little bit easier to see, even with a weaker telescope. Zooming out just a little and the rings become really difficult to see. They’re so narrow, unless your telescope has a really good resolution, unless it’s able to resolve this in a lot of detail, we’re going to miss the rings. As we pull back a little bit, we’re not seeing that kind of loop, that little curve at the side of Saturn which we would see if we were seeing the rings at a slightly better angle. We’re seeing Titan pretty well, Titan can be seen moving around the planet over different dates around its opposition. On the 22nd it’s pretty far out from the planet and easier to see. These are good times to take a look at Saturn, we can see Titan out nice and far, the planet is facing us and it is fully illuminated, it’s going to be at its brightest. We’re not really seeing any of the shadow of Saturn, just a tiny bit on either side. If Saturn wasn’t at opposition, we’d be able to see more of its shadow falling on its ring, but because it’s at opposition the shadow of Saturn is directly behind it on the ring, and that pretty much blocks it from our view.

Moving forward to the 23rd there, a little bit after Saturn’s opposition, brings us to Neptune’s opposition. I know that Neptune is around Saturn somewhere because their very close together at the moment. What we’ll do is push out into the countryside where, of course, we’ll get a better view of everything. We’ll certainly get a better view of faint objects like Neptune, and with a little help from the labels provided by Stellarium, it can be spotted just next to Saturn. Now, of course, you need a very big telescope to take a closer look at Neptune. Just like Saturn, it’s 100% illuminated as well and we’re seeing it from 28.884 AU away. Moving around a couple of days, and the distance ends up going up to 28.885. This happens whether we go backwards or forwards, meaning that 23rd is when Neptune is going to be at opposition. Of course, with these distant planets, roughly at opposition is often good enough, they’re going to appear fully illuminated. They’re going to be pretty much at the closest they’re going to get, and they’re so far away that the closest they’re going to get isn’t going to be particularly close anyway.

We can see a selection of Neptune’s moons as well and its largest moon, Triton. Triton, similar to Titan, is very reflective though for a different reason. Over the course of different nights it can be seen moving around Neptune, it stays pretty visible and it is very bright. Of course, you’re still going to need a much larger telescope to see it, but it’s easier to see Triton around Neptune than it is to see Neptune’s other moons, and it’s similar for Saturn and Titan. They’re still quite close together in the sky as we move forward to the dates of their opposition and will stay that way for a while as they move so slowly. If you find Saturn, Neptune is going to be very close by and it does have that slightly bluish color. Of course, even seeing both of them clearly requires a view that is quite a close up. Just seeing Neptune as a bluish dot is already enough magnification to see some of Saturn’s moons. Even that might be a little bit difficult to achieve, and of course that brings us back to the 22nd, all the way forward to the equinox.

Coming a little bit back towards sunset, now that we’re closer to the end of the month, Scorpius will be setting by the time the sky is dark. The Milky Way is out, but because the Milky Way is passing through the summer triangle we know it won’t be up all night. We will be losing the bulk of the Milky Way by the time we’re through to about 2 o’clock in the morning. We’re really only seeing the outer edge of the Milky Way once the Sun starts to rise, so we’re not seeing as much of the Milky Way in September as we did in previous months. We’re still able to see quite a few planets, but Mercury will be after leaving the morning sky. It will be back in the evening sky pretty soon of course, Mercury orbits the Sun quite quickly, so it won’t be too long before we see it again.

That pretty much brings us through to the end of September, so I hope that you get to see a few of these things as they come up. If you enjoyed this video, then please do like it, and if you like this kind of content, please subscribe to this website and my YouTube channel. Thank you very much for reading and hopefully I’ll see you back here next time.