Caoimhín's Content

In this piece we will continue looking ahead into the month of October, but focusing on the constellations. Last time, we looked ahead to see where the planets are going to be and some of the other things we will be able to see in the sky, such as meteor showers. In this piece, I’m going to concentrate on how the constellations have changed. I often mention the more famous constellations, such as Orion, as they become visible in the sky, but it has been a while since I committed time to describing the layout of the constellations more generally.

Beginning by looking South from a city, with the light pollution that entails, and early enough that there’s still a little bit of sunset glow. Already, there will be a few constellations visible. The Summer Triangle will certainly be up, but it is only an asterism. However, if you can see the asterism of the Summer Triangle, then you can see the three brightest stars in three different constellations. Out of the top, or more Northerly, two stars, the fainter one is Deneb, the brightest star in the constellation Cygnus, while the brighter star is Vega in the constellation Lyra. Down at the bottom, or to the South, is the bright star Altair in Aquila. We’ve definitely got those three constellations visible by their brightest stars as the Sun sets. Down towards the horizon in the Southwest you might see bits of Sagittarius, but of course anything that’s very low to the horizon, especially if you’re in a city or if you’re in a valley, can be blocked from view.

Turning around towards the East, Cassiopeia is visible high towards the Northeast. The Square of Pegasus is also up nice and early, along with the constellation of Andromeda. Both the Square of Pegasus and Cassiopeia can be used to help find the Andromeda Galaxy between them, in the constellation of Andromeda. Even if we don’t get to see it from the city, it has to be in that position of the sky. Continuing to turn around, looking towards the North, of course we’ve got the Plough or Big Dipper. At this time of the year, the Plough will be low towards the Northwest, pointing up towards the North Star early in the evening. At different times of the year the Plough will be in a different position around the North Star at a given time. At the moment it is down towards the Northwest early in the evening, but as we move through the night of course that position will change, and as we move through the year it will be in a different position at sunset. With the Plough almost under the North Star, Cassiopeia will be almost above the North Star on the opposite side. Just using your eyes, even from the city, even with all of the light pollution, there are a number of constellations visible in the sky.

Saturn is easily visible in the city, meaning one of the zodiacal constellations, or Signs of the Zodiac, must be around here, because that’s where Saturn is. Saturn is a planet and so it follows the ecliptic across the sky. The ecliptic is a very particular line which is pretty much where the Sun’s equator would be if you stretched it into space. All of the planets roughly orbit the Sun’s equator, and along that line is where the famous zodiacal constellations stand. Behind Saturn must be Aquarius. Capricornus is between Sagittarius and Aquarius, and Sagittarius is at least partly visible at the horizon. Directly following Aquarius is Pisces and then Aries, though both of those constellations can be a little trickier to spot. If the lines of the constellations are brought up, as they can be in Stellarium, the constellations are a lot easier to find. With these lines you can definitely see, from here in the city we’re missing so many stars thanks to light pollution, that we are missing entire constellations. Not just small ones either, it’s almost impossible to see any of the stars in Pisces, which is a pretty big constellation, if you’re dealing with the light pollution in the city. We can see the shape of Perseus under Cassiopeia, with it’s fin like shape. Another distinctive shape roughly in the East is Auriga with the bright star Capella, which has a nice pentagonal shape.

The lines connect together that stars involved in the constellation, but it can still be tough to tell what they are meant to represent without the actual images. Bringing up the images or pictures we can definitely see that the sky is packed with constellations. This also helps to confirm that it is Aquarius with Saturn, the lines of Aquarius alone don’t really look like the picture it’s supposed to create, but we know Aquarius is between Capricornus and Pisces. If you know the order of those constellations, even if you don’t recognize this line in the sky as Aries, if you know recognize Pisces and Taurus, Aries has to be the one in the middle. Luckily at least some of the constellations have a more recognizable shape, like Sagittarius.

A less famous constellation with a clear shape is the constellation of Triangulum just under Andromeda. In the same way that Andromeda has the Andromeda galaxy, Triangulum has the Triangulum Galaxy, another one of the Milky Way’s very close neighbours. Moving forward towards morning time, some more planets will rise into the sky, which means more of the zodiacal constellations coming into the sky as well. Mars is in Gemini at the moment, with Jupiter in Taurus. Cancer is another very tough constellation to spot, but with the more famous Taurus and Leo either side, it is still possible to find. Leo will be fully risen just ahead of the sunrise. A little bit of Virgo will rise before the sunrise as well, but it may be difficult to see any of it’s stars, especially from the city. By the end of October, the Sun will be at the very end of Virgo and is closer to the head of Virgo at the moment. Things have changed a lot since Ancient Greece, not least the calendar, but in the modern day if you were born at the end of October, or really any time in October, the Sun was in front of Virgo on the day that you were born. Of course astronomy and astrology are very different things, but in astronomy, Virgo is where the Sun actually is in October.

Turning to the North with the pictures of the constellations visible, we can see that the Plough is really just part of Ursa Major. Ursa Minor is visible connected to the North Star. We can also see the kind of “kids drawing of a house” shape of Cepheus. Cepheus and Cassiopeia are next to each other in the sky, and of course they are related to the whole story of Perseus and Andromeda. I have a whole piece dedicated to that Ancient Greek story much further back on this website. From here, we will move back towards the middle of the night, getting rid of all of the pictures and then all of the light pollution. Moving all the way to 9:30, reasonably early in the evening, we will then push out to the countryside, to see the constellations from a dark sky.

From a dark sky, there are loads more stars visible, and that can occasionally make things more difficult. For example, looking into the summer triangle, you can certainly see all of the stars in the constellation Cygnus, but there’s a lot of other stars up there as well and it can be easy to get mixed up. Looking at another corner of triangle, we can see the stars that are part of Lyra, but it’s easy to forget how few there are, it’s a pretty small constellation. With so many stars in the sky it can be easy to get mixed up, especially if you’re looking at fainter constellations, for example the constellation of Pisces. You can see the faint V-chape forming the lower part of Pisces, but these stars are pretty faint. They are visible, but it’s very hard to tell, with so many stars in the sky it can be difficult to pick out exactly what ones you’re looking for. It helps to look for particularly recognizable groups like the Hyades. We know the Hyades are part of Taurus, and if that’s Taurus, Aries must be just next to it, passed the Pleiades westward of the Hyades. The lines of course make it a lot easier, but with the lines in the sky it’s also easy to see that they are joining together some of the brighter, more prominent stars. It is almost always the brighter stars in an area that are used in constellations, but the margin between those stars that barely qualify as bright enough to use, and the stars that narrowly miss that level of brightness, can be narrow. In certain constellations, it can be hard to tell which stars are included, or even why certain stars are included and not others. The lines used in constellations, and what stars exactly they join, were unofficial for a very long time. Constellations we’re almost an unscientific thing, a colloquial thing, and various different groups around the world would all use different lines and make different pictures. Even from place to place within the same culture, the same pictures could be described using different stars. However, they were eventually standardized, the official constellations were set, and rules were set for which stars are included.

Even then, there’s some odd stuff preserved in the modern constellations. With the lines of the constellations visible, it’s even easier to see that some constellations join together. Some stars are included in two constellations, forming a link or bridge between two images that are considered separate. Looking towards Andromeda and Pegasus, we can see that Andromeda connects to one corner of the Square of Pegasus. This star is Alpheratz, and it’s counted as Alpha Andromedae and Delta Pegasi. Another example is just above the Hyades in Taurus, with the star Elnath. Elnath is both Beta Tauri and Gamma Aurigae, and it visibly joins those two constellations together, though calling it Beta Tauri is more common today. There are still some strange rules when it comes to the constellations in the sky, but which ones you can see does depend on whether or not you’re in the countryside or in the city. Some of the fainter constellations will lose all of their stars if you’re in the city, but if you’re in the countryside it can take a little bit more practice just to pick out the stars that are important, the ones that actually make up the constellations, especially if you don’t have the lines to help you. One example of this is Gemini. The two brightest stars, Pollux and Castor are very clear and obvious. However, remembering exactly what other stars form part of the constellation, even if you have recently seen the lines, when all of these other stars are visible as well, can be a little bit trickier,

We will come back to the beginning of the night facing South, There are some constellations that are recognizable even if they’re very small, like Delphinus just next to the Summer Triangle, about halfway between Deneb and Altair. It is a tiny constellation, but it’s easy to spot thanks to its very clear rhombus shape. That stands out, and of course the fact that that shape stands out is part of the reason it was made a constellation. The prominence of these shapes are what made people call them constellations to begin with. There is a reason that each individual star was picked out, they do stand out a little bit from the background, whether it’s their shape as a group or their individual brightness. We can see this again with the kind of ring-shape near Arcturus in the Southwest. That is the constellation Corona Borealis, where a supernova is supposed to happen very soon, if hasn’t happened already. Of course, we’re looking a little bit into the future here, there is a chance that this supernova will have occurred by the time this future date will arrive in October.

Turning around to the North, in a reasonably dark sky we’ll get to see a little bit more. It’s a lot easier to see the rest of the shape of Ursa Major, the other stars around the Plough that make up the full constellation. If we look up to the North Star, you can pretty easily make out the shape of Ursa Minor, or the Little Dipper as well. The stars in Ursa Minor are a little brighter and they have that more distinct shape. Bringing up the lines to help, of course there’s lots more, there’s a lot of less famous constellations in this direction. Draco the Dragon is one, and despite being a very big constellation and in a very interesting, well known part of the sky, it doesn’t get as much attention as the Bears do for example, or Cassiopeia. Draco is on the opposite side of the North Star to Cassiopeia and the Milky Way, and being right on the glow of the Milky Way of course makes Cassiopeia an interesting target and adds to its fame. In the same area, just below Cassiopeia and Northwards from Perseus, is Camelopardalis, another pretty obscure constellation. Camelopardalis isn’t a very big constellation and it’s not very well known but it is up there to be seen and if you are in a dark sky. Even without the pictures, it does have a sort of triangular shape, and it’s near to this fin of Perseus. For some of these fainter constellations that are difficult to see, it’s easier to use the more famous constellations kind of like signposts, to help you find the fainter ones. For example, if you’re trying to find out where Draco goes, it passes between Ursa Minor’s head and Ursa Majors tail, so Draco must extend out of a pretty restricted region of the sky. This can help even if you’re in the city,

To finish up with this look ahead to October’s constellations, we’ll come back to a city sky. With 88 constellations in the sky, I don’t think I’ll ever be able to deal with all of them in just one video, unless that video is very, very long, so of course there are plenty more visible at this time of the year that I haven’t mentioned. Looking into the southern sky as the Sun sets, Delphinus is basically invisible, maybe you can see a couple of the stars there if you’re eyes are good enough. Thankfully, we can see the summer triangle and Delphinus is just off one side of it, along the line between Deneb and Altair, which we can see. Even if you can’t see the constellation, sometimes you can figure out where it is, or what constellation is supposed to be where, by looking at the more visible constellations. Looking back at Camelopardalis from the city, maybe one or two of its stars will be visible, but it’s basically invisible to me at least. However, the fin shape of Perseus is visible and Camelopardalis is just next to it to the North. We can use that to fill in the gaps, figuring out where stars would be visible if it weren’t for the light pollution. Looking up to Ursa Minor, there are only a couple of bright stars between it and the tail of the Plough, so they must be the stars in Draco, it is usually the brighter stars that get made parts of these constellations.

I do hope that you get a chance to see some of these constellations in the sky, whether it’s from the countryside or from the city. If you enjoyed this piece then please do like it and if you like this kind of content please do subscribe to my website and my Youtube channel so that you’re more likely to see more of it. Hopefully, I’ll see you back here next time.