Caoimhín's Content

We are back to looking a month ahead, to see what the sky will look like in May as we come to the end of April. In the last video, about a few meteor showers, we touched on the Eta Aquariids, which are one of the big astronomical events in May, but the sky is everchanging so there’s more than just that to see this month. Going from the 30th of April to the 1st of May of course the sky won’t have changed much. As the sky darkens and the stars emerge, we can see that Leo has moved little to the West of South and we can see the diamond shape of Corvus is almost due South, rather low in the sky, at just about 10:45. This is reasonably late, but we need to go reasonably late for the sky to actually be dark enough once we’re into May. If we push through into mid-May, to the night of the Full Moon, not only will the light of the Moon effect our view, there is still a glow from the setting Sun as late as 10:45. By later in May, we’ll have to wait until 11:30 before all of the Sun’s light has left the sky. The very short Winter days in higher latitudes like Ireland are complemented by very long Summer days. Having to wait until 11:30 for actual darkness is certainly downside from the perspective of astronomy. However, with the constellations shifting in the sky and night-time starting much later, we can start to see Scorpius rising in the East by the time the sky is dark. Just a few weeks ago Scorpius was firmly a morning time constellation, but this is starting to change now. This also means that the glow of the Milky Way will be in the sky by the time the sky is dark. The Summer Triangle is also visible further East, so even in a city sky we know that the Milky Way is up, even if we can’t see it. Of course, it isn’t quite summertime proper yet, but the Triangle is certainly starting to rise at sunset. Although it isn’t fully above the horizon at sunset yet, it is fully risen quite soon after darkness, and so the summer triangle is almost with us all night long. It will really be with us all night long as we come into June and July.

Moving on towards morning time, even quite early in the morning Sagittarius is practically in the South, meaning that in a dark sky, the Milky Way should be rising almost straight out of the South by the time the Sun is starting to rise. Later sunsets also come with early sunrises, we’ll be seeing the glow of sunrise as early as 3:30, even though the Sun won’t be up until a little closer to 4 o’clock. Just ahead of sunrise, Saturn is definitely getting visible, at least once we’re later into May, even in the city. Saturn is still quite low in the sky, especially when it first rises while it’s still dark, we’ll have to wait a little bit longer for Saturn to get higher in the sky. Mars is just barely visible low in the sky while the orange glow of sunrise begins to appear, even right through to the 31st of May, Mars will still be too low in the sky and swamped by the orange glow of sunrise, while on the same dat Saturn has a lovely close conjunction with the Waning Crescent Moon. Taking a look at the morning time constellations, Mars is next to the sun in Pisces and Saturn is further over in Aquarius. Capricorn is just between Aquarius and Sagittarius, but it is a trickier constellation to spot. The Summer Triangle is nice and high in the sky by morning time and, as mentioned in previous posts, it is only an asterism, a shape separate to the constellations of Lyra, Cygnus and Aquila, whose brightest stars form the Triangle. The Square of Pegasus is going to be to be just above the sunrise by morning time, and even while the sky is still reasonably dark as we come to the end of May. At the beginning of May it’s not in a great position until the glow of sunrise is already in the sky. Pegasus will of course be joined by the constellation of Andromeda and the Andromeda Galaxy. Between Andromeda and the horizon, just above and a little north of the sunrise, is the the constellation Triangulum with the Triangulum Galaxy. The Andromeda Galaxy and the Triangulum Galaxy are two of our closest neighbours, with Andromeda being a little bigger and closer and so much easier to see. They are both quite close to the glow of sunrise in early May, but as we reach the end of the month they become a viable target for binoculars and small telescopes early in the morning.

In a countryside sky free of light pollution, Andromeda may even be visible to the naked eye is you catch it in true darkness before sunrise. Looking at the sky at sunset without any light pollution allows a lot more stars to be visible even while the sky is lit by the setting Sun. Even at 10 o’clock it’s still quite bright, but we’ve got a very clear view of constellations like Leo and Gemini. Virgo is never really a clear constellation, many of it’s stars aren’t particularly bright and it doesn’t have a very recognizable outline. Thankfully, Spica, the brightest star in Virgo is prominent and stands out clearly. Above Virgo, about the same height in the sky as Leo, you might be able to see the kind of kite-shape and in the tail of the kite is the bright star Arcturus. The kite shape is really the constellation of Boötes, which is meant to be a person, but the lines of the constellation look much more like a kite to me. Continuing across the sky, away from Leo and past Boötes lies Corona Borealis, in between Arcturus and Vega in Lyra. This constellation is where we’re going to see what appears to be a brand new star thanks to a recurring nova. It won’t be a supernova, but a nova can be very bright as well. It’s going to happen this year at some point, though we may need to wait until September before it actually occurs. There is a video and article all about this upcoming nova posted just a week or two ago. As soon as we push a little bit later, thanks to being in the countryside we’ve got that lovely view of the Milky Way. Even in early May, as early as midnight and we have a lovely view of the Milky Way stretching through the Summer Triangle. The shape of Cygnus stretches out from the bright star Deneb, the corner of the Triangle high on the Milky Way’s path. At the head of the Swan, almost the very middle of the Triangle, is Albireo, a bright binary star. There was a video recently on this channel about binary stars and Albireo is one of the best. If you have a good enough telescope, one star will turn into two as you look closer. Not only does the star appear to split, it is revealed to be two stars of different colours, a contrasting cool blue-white and warm yellow-orange. The blue star is smaller and very hot, but a little fainter than the orange giant it is next to, which is much larger and cooler, cooler even than our Sun. It seems like these stars aren’t orbiting each other, but are almost aligned from our perspective.

Pushing through to the morning sky under dark conditions, Sagittarius will rise fully above the horizon early enough that you can take in the full teapot shape before the sky gets to bright. With Scorpius, we will still be missing the Tail and Sting of the Scorpion, as that ducks under the horizon for us here in Ireland. Saturn is definitely quite visible in the countryside, followed by Mars, which is still a little tricky to spot, but easier to see than in the city at least. Later in May, Mercury will reach its Greatest Western Elongation. Mercury has two different greatest elongations, one to the West which we see in the morning and one to the East which we see in the evenings. Although Mercury will reach it’s furthest out from the Sun, it stays really close to the horizon, so Mercury ends up with the same problem here as Saturn and Mars had earlier in April. It looks like it’s not really going to be visible for us here in Ireland even at its greatest elongation. This is mostly thanks to the time of the year and the angle at which we’re seeing the Sun rising and setting. At other times of the year, or if you are at a lower latitude seeing the Sun rise at a steeper angle, it will be much more visible.

Early May is probably the best time of the month for stargazing thanks to the New Moon, there will be no moonlight in the sky to block out the Milky Way and other faint object. It is also when the Eta Aquariids will peak. I did cover a bit about them the last video but they are a feature of the May sky. They will reach their peak around the 5th and 6th. Thanks to historical records of meteor showers, and some understanding of the reasons behind variations in their intensity, it is possible to predict to a degree how big a certain meteor shower is going to be. How ever, the predicted numbers are approximate, you never really know how many meteors you are going to get to see in the sky until the meteor shower happens. There’s almost always going to be some variation, some of which is predictable, but occasionally there are still surprises. Going by the predicted values, the peak of 50 meteors passing the zenith in an hour, they will peak while the radiant is under the horizon for us here in Ireland. Luckily this doesn’t matter too much, as meteors can appear almost anywhere in the sky. If they are Aquariids, then they’re trail will still point back to their radiant in Aquarius. They also happen to peak around the night of the New Moon, making it both a perfect night to see the see the glow of the Milky Way and a meteors shower at the same time. The Eta Lyrids are a much more minor shower which will be peaking later in May. They are far less intense than the April Lyrids, but they are a good example of why months or Greek letters are needed as well as the constellation to specify meteor showers, just saying the Lyrids can be too general. Of course, some showers are commonly referred to by just one name, such as the Leonids and Perseids, sometimes the Geminids and Lyrids as well.

As our orbit around the Sun doesn’t line up with the orbit of the Moon around us, whether or not a meteor shower happens during the Full Moon or the New Moon will vary year by year. This year, the April Lyrids were pretty much blocked out by the light of the Full Moon, so we didn’t have much chance to see them at all. Luckily the Eta Aquariids are going to be peaking closer the New Moon giving us a better view. This situation will no doubt be reversed in just a few years. Meteor showers also differ in how much the Moon will impact them. A meteor shower producing very many small meteors is much more likely to be obscured, where as a meteor shower that produces few, but bright and occasionally explosive meteors may have some visibility even in a brightened sky. Different kinds of objects can leave behind different types of material along the Earths path, and that will affect the kind of shooting star or meteor that you see in the associated meteor shower. The Eta Aquariids come from a trail left behind by Comet 1P/Halley, the first confirmed periodical comet, with a period of about 76 years. It should be back around again in 2061, but it leaves behind this trail of material and that’s what we get to see with the Aquariids. Even if it will be a while before the main comet returns, little bits of the comet are what you see burning up in our atmosphere during the meteor shower, almost like getting to see part of Halley’s Comet early.

We may of course look at some of these things in more detail as we come up to them during the month. As well as the interesting things we will definitely see, it’s worth keeping on eye out just in case the nova in Corona Borealis does happen this month. I hope you enjoyed this little preview of the coming month, I put up a preview like this every single month, as well as covering other topics in astronomy to bring the number up to two a week, including at least one a month in Irish. If that sounds like the kind of thing you like, you can subscribe to this website, my YouTube channel or even find me on Instagram under Caoimhín’s Content. Hopefully that will bring you back here for the next post.