Caoimhín's Content

Today, we are going to be taking a look at the night sky in September again. We will be looking at the sky for the month coming up, but we will be concentrating on the stars. There are so many exciting things coming up in September that in my previews of this September so far I’ve concentrated on those other things. We’ve got so many interesting things, eclipses, conjunctions, occultations, all going on this September, but we do have the stars as well, which will look as they do in September every year.

Starting with sunset early in the month, once the sky darkens Antares and Scorpius are visible low towards the southwest. The curve of Serpens is visible just above it, and so Ophiuchus would be up around there as well. The summer triangle is high in the sky as soon as it appears, along with other bright and famous stars, like Arcturus just above the sunset. There’s a lot of the more famous wintertime stars starting to come into the sky in the east. We’ve now got the Square of Pegasus completely up as soon as the Sun goes down. Extending east from there would be Andromeda and above it we’ve got Cassiopeia. This means that the Andromeda Galaxy is up pretty much all night long, it will be reasonably high from sunset at least. Andromeda is more or less circumpolar, meaning it is always above the horizon, but it can often be very low to the north. We won’t have to wait too long for it to come up from lower in the northern horizon at this time of the year. Turning around to the north we have the Plough or the Big Dipper over in the northwest, pointing up to the North Star. As the night goes on, the Plough is going to move more and more under the North Star as we come later and later in the evening.

As usual, to start with this view is from a city sky, but we will move out into the countryside and lose the light pollution a little bit later. We’re after coming all the way through here to a local midnight or physical midnight. We’re still in summertime here in Ireland, meaning we’re at UTC+1, one hour ahead to account for the longer days. For us seeing the sky at 1:30, it’s really 12:30 if it wasn’t for the additional hour, and it’s really our local midnight, which needs to be adjusted because we’re so far along in our time zone. By this time Saturn is nice and high. Saturn nearly at opposition, so it’s going to be with us all night long, and we’ll take a closer look at Saturn a little bit later. Also by this time, the summer triangle is already sinking down on one side of the sky, and we’ve lost Scorpius and Sagittarius. We’ve got the Square of Pegasus and therefore the Andromeda Galaxy much higher in the sky, so it’s going to be even easier to observe. Moving later Capella the star comes up, part of the constellation Auriga, with a kind of pentagonal shape, nice and easy to recognize even from the city.

Coming up to morning time, sunrise will be getting later. We’re still early in September, so morning time is still a little bit early, we’ll have to move later in the month for these stars to come up closer to midnight and for the sky to remain dark for longer. Orion will be well above the horizon before the glow of the Sun comes up, and above that we’ve got Aldebaran with the Hyades marking the head of Taurus. Continuing a little higher in this direction are the Pleiades. Taurus extends from the Hyades to the Pleiades in one direction, with its horns stretching up in the other direction to the bottom of Auriga. Just across from Taurus and under Auriga is Gemini the Twins. We’ve got more of those famous things coming into the sky as we push later in September. For the very early part of the month we’ve still got Mercury atg sunrise, but as I said, we won’t worry too much about the planets. Even moving forward a couple of days makes a difference to the morning sky. It’s darker for longer so we can see these things a little bit more clearly. We’re seeing them a little bit easier because as we move further and further into September, we’re going to have our longer nights which means earlier sunsets and later sunrises. For stargazing and astronomy, that’s perfect, that’s what we want, we don’t get to observe quite as many things during the day.

Moving forward to September 4th, before we go further into the countryside or before we take a look at the constellations in more detail, we’re going to look at Saturn. I was told that Titan would transit Saturn, and it at least very nearly does, but it looks like this isn’t going to be visible from Ireland. Using Stellarium we can get rid of the ground and the atmosphere to follow Saturn under the horizon to see if it is going to be visible. Thanks to the tilt at which we see Saturn, we don’t usually see, we don’t usually see Titan passing directly behind or in front of the planet, so it’s usually very visible. By looking at the moons of Saturn over time, it’s clear that they’re definitely orbiting Saturn’s equator. A lot of them, especially the moons that are closer to Saturn, they do regularly transit or get occulted, they go in front of or behind Saturn. However because Saturn is a little bit tilted, further away from Saturn objects following its equator are going to look like they’re forming an ellipse around Saturn, a very eccentric ellipse, which is very different to how their orbit would look from above. From our latitude here in Ireland, it does look like Titan is passing almost in front of Saturn, just not from our longitude. There’s a good chance that that would look slightly different from other locations, as I’m basing this off of our view from Ireland, looking through the ground. It’s happening not too far under the western horizon. This won’t be visible from here in Ireland, but it should be something you can check out if you’re a little bit further west than we are here in Ireland.

Getting back to a normal nighttime view form Ireland and we’ll push out into the countryside. There’s plenty more stars visible in the countryside and we’re also going to see things a little bit earlier. We do have the Moon in the sky, but of course, the Moon is going to be up in the sky for much of the month. It just stops being new just before the month begins, so we’re going to get our Full Moon a bit before the middle of the month and the New Moon won’t come until close to the end. We will take another look at Saturn later in the month because there is supposed to be another transit of Titan. Now we can see our brightest stars coming out nice and early, at just 8:30 we’re already getting bright stars in the sky. We can see a little bit of Mars right above the horizon, but it’s not going to be easy to see for us, it’s very close to the Sun sunset. Antares appears earlier so we can see it a little bit higher in the sky just as the Sun is going down. The summer triangle and the Square of Pegasus are also visible nice and early. Pushing just a little bit later and Saturn pops up above the horizon just as the sky really starts to darken, just coming up to 9 o’clock. Sagittarius is particularly clear and easy to see in the south/south-west. At other times of the year, when we see Sagittarius in the south, the angle at which we’re seeing it can put some of its lower stars under the horizon, but we’re seeing pretty much all of the core stars of Sagittarius and we’re already starting to see a little bit of the Milky Way.

Now, of course, I’m simulating and assuming a perfect dark sky, with absolutely no light pollution. It’s very difficult to achieve skies like this and dark sky parks are the best place to do so. Close enough to the Full Moon, the light of the Moon is definitely having an effect on our view. If we move away from the Full Moon later in the month, then we get a much better view of the Milky Way. At the right time of the month, the Milky Way is starting to appear as we come past 9 o’clock, definitely by a little after 9 o’clock. At close to 9:30, the glow of the Milky Way is nice and clearly visible. We’re able to see the same stars, of course, but we’re able to see much more of them and that lets us see smaller constellations like Delphinus for example. However, with so many stars in the sky, it can also be difficult to keep track of exactly what constellations are what. Stellarium can provide the lines that make up the constellations, that makes it a lot easier to see constellations like Corona Borealis and Hercules.

With the actual pictures in the sky, all the constellations are easy to see. In this view Saturn appears to be in front of Cetus the Whale, but it is probably in Pisces. With the border lines of the constellations, we can double check Saturn’s position, and it is over the line in Pisces. Even though it looks like it’s in the image of Cetus the Whale, the drawings of the constellations don’t always perfectly line up with the actual breakup of the sky and how things are divided. While we’re in the countryside, if we take a look over to the east, we’ve got the Square of Pegasus and Cassiopeia still clearly visible. We know that both of those constellations point roughly to the Andromeda Galaxy. Thanks to the dark sky, it starts to become visible really quite early as we zoom in. By going across the Square of Pegasus from west to east, we get pretty close to the galaxy, though it’s a little bit higher. By going through the better triangle of Cassiopeia, higher on the milky way, from the north, we also get pretty close to Andromeda. With these two guids it shouldn’t be too hard to find, as it is a very large galaxy, even though it’s very distant from us. With a big binoculars or telescope we can see it very clearly. While we’re zooming in on things, we’ll take a look for the Triangulum Galaxy. It is just a little further south, lower in the sky, than the Andromeda Galaxy. It is just to the side of the Triangulum constellation, outside the picture of a triangle but within the bounds of constellations area. Triangulum is also one of the easiest ones to see, it’s another very close neighbor, our next closest neighbor after Andromeda. With a wide field of view little bit zoomed in, we can see the shapes of both of those galaxies, but the Andromeda Galaxy is the one that’s visible to the naked eye, if you are in perfect conditions.

Continuing along to morning time and just as we get the planets rising, we can see some of the other constellations. A little bit before the Sun rises, we’re just getting the Moon coming later in the month, with Venus just next to it on September the 19th. You might even be able to see a little bit of Cancer the Crab. A couple of the stars in the Crab are visible in the countryside, and they are up before the sky gets too bright. There are also some of the other faint, less famous, constellations up, such as Cetus and Eridanus. While we’ve got the Moon and Venus so close together, we can see that they get particularly close. They might not visibly get as close as possible from here in Ireland, just because we’ll get into daytime. We’re not going to be able to see the Moon occult Venu, they’ll just have a particularly close conjunction from here in Ireland. However, there is an occultation of Venus happening during the day, so with the right equipment like a solar telescope it could be seen. I’m pretty certain that I’ve already taken a look at that in a previous piece, but it’s always nice to have a little reminder of what’s going on in the sky as we look around.

That’s a little bit about the stars and the constellations that we’re going to see in the coming month, as well as Titan and Saturn being very close together. I hope you get to see some of these things in the real sky, and I hope you get to see the sky in real darkness. Remember, it is very hard to see the sky with as much darkness as Stellarium can simulate, even in areas that you might consider the countryside. Official dark sky parks are places where these things are definitely this dark, so if you have any of those near you, they’re a particularly nice place to visit. I hope that you enjoyed this piece, if you did then please do like it and if you like this kind of content you can subscribe to this website and my YouTube channel. Most importantly, thank you for reading and hopefully I’ll see you back here next time.