Caoimhín's Content

Today we are looking at the Perseids again. I did take a quick look at the Perseids last year at around this time, but they are such an impressive meteor shower they deserve to be mentioned again. Starting right at sunset will mean that the Moon is in the sky, but very low to the West, it won’t be a factor for most of the night. We’re specifically looking at the 12th of August, the night that the Perseids expected to peak. A lot of people live in cities so chances are you live in a city and that you will be observing these from the city, it’s not ideal but it is likely, and even with some light pollution you might see a few Perseids. However, I must recommend heading out to the countryside, where far more shooting stars will be visible.

Although the night begins with the Moon in the sky, it sets just after sunset. The Moon will be going down about the time that Saturn is coming up, and the Moon will be out of the sky by the time the sky is at a good level of darkness. As we are pushing away from summer, we will have a reasonable level of darkness as early as 10:30, not too late at all. Starting by looking into the South here, you can tell by the summer triangle reasonably high towards the South, we need to turn over towards the Square of Pegasus just a little towards the East and below the summer triangle here. Moving across the Square of Pegasus from West to East points us in the direction of the Andromeda Galaxy, which is also pointed to by the W shape of Cassiopeia. More directly under the W of Cassiopeia, further East again than Andromeda, we have the constellation of Perseus, where the Perseids radiate from. There are a few radiants of active meteor showers right now, including the ever present Antihelion point, as well as the Southern Delta Aquariids and Alpha Capricornids. You can learn more about these in one of my recent pieces, but they are tiny meteor showers that do not contribute many shooting stars to the sky. Both of these showers will be contributing roughly 0 meteors to the sky on the 12th, despite peaking with a maximum ZHR of 30 for both taken together. The ZHR is the zenith hourly rate, a rough measure of how many meteors you will get to see in the sky.

Moving over to the Perseids, they can get to a ZHR of 100, and it looks like we’ll be seeing it at about 85 ZHR from Ireland this year. This is quite a high rate of meteors. The local hourly rate will fluctuate between different times of the night. However, they will stay reasonably high through the peak on the 12th. The Perseids technically run from the 16th to the 24th, but this long duration can cause a little bit of an issue. There are many meteor showers that run for a long time, but their peak is often just one or two nights. When people say for example, “Oh, the Perseid meteor shower is on, it’s one of the best meteor showers of all year, you should get outside and take a look at it because the meteor shower has begun, the Perseids are on going.” Yes, but at the begining of August they are at 3 ZHR, lower than what would be considered a minor meteor shower. The Perseids run for a long period of time but they peak on one, maybe 2, nights of the month, the night of the 12th going into the morning of the 13th. Generally, you do get a few extra ones on the days before or after, but the peak of the Perseids is quite constrained. Moving ahead from the 12th at 85, the ZHR drops down to 55 the next day and just 35 the day after that, then 20, 14, 9, and basically not running at all within a few days. The same is true if we go backwards, from 85 to 76 on the 11th, 49 on the 10th, then 31, 20, 13, 8. We will barely be seeing any from anytime before the end of the first week of August, even though it starts in practically mid-July, on the 16th of July.

I don’t want people to be disappointed when they go outside stargazing, that’s why it’s so important to me to say when things are difficult to see. I do my best to indicate when things are invisible from my latitude here in Iralnd, or when they would be obscured by light pollution form a city. For the Perseid meteor shower, I think it is equally important to say that if you’re not out on the night that it’s peaking, you may not see many meteors. This can be disappointing. If you’re told that it’s one of the best meteor showers of the entire year, which it is, but then you go out and don’t see any meteors at all, that is understandably disappointing. I don’t want people to be disappointed with the sky, and the Perseid meteor shower is fantastic on the 12th of August, so that’s when I want you to go looking for it, if you can get out into the countryside to see it, even better. However, I don’t want anyone to be let down by going out in July or early August looking for the Perseids and seeing very few meteors, unless you are prepared for that to be the case. If you know that seeing any meteors is a long shot and you want to try anyway, then of course you should, I’m sure you’ll find things in the sky to enjoy regardless.

One of the reasons that the Perseids are a fantastic meteor shower is that they’re one of the most reliable. Over the past couple of years the amount of meteors we’ve seen in the sky at peak has varied up and down between about 100 and about 60. That’s a pretty tight range, quite a good range for a meteor shower. The Perseids don’t have incredibly high spikes the way the Leonids sometimes do, but they also don’t have incredibly minimal periods,. The average Leonid shower isn’t as good as an average Perseid shower, even though the most exceptional Leonid showers can produce a lot more meteors. The Perseids are more consistent, they’re more reliable, as long as you go out on the dates when they actually peak, on the 12th and into the morning of 13th.

The shower will run through the night, so starting from sunset we can continue closer to midnight, which brings the radiant of the Perseids a little higher in the sky. Although this is where the meteors radiate from, they can be seen across a big portion of the sky, even if the radiant itself is below the horizon. However, this also brings Perseus higher into the sky. The constellation Perseus is in the outer portion of the Milky Way, and is circumpolar from Ireland. This means that it never sets, but being pretty much at the edge of circumpolar in Ireland, it may set at lower latitudes. However, for most of the Northern Hemisphere, it won’t ever go very far below the horizon. The radiant and the constellation continue to get higher as we get closer to morning time. Once the Sun starts coming its light will block out a lot of the meteors, but this year we only have to worry about the Sun coming up. The year before last, the Moon was very close to full on August 12th and that made the Perseids almost impossible to see due to the light of the Full Moon. This year we’ve got a narrow Waxing Crescent Moon just next to sunset, so we won’t have to worry about the extra light. This makes the night of the 12th a pretty good night for looking at faint objects more generally. I’ve mentioned plenty of times in recent articles just how amazing the sky is in August, especially in early to mid-August. With so many planets in a row, including Neptune as you might remember from my previous post, with at least Jupiter, Mars and Saturn visible to the naked eye and maybe Uranus under good enough conditions. Speaking of Mars and Jupiter they are going to be very, impressively even, close together in the sky on the morning of the 13th. They do get even closer over the next couple of days, but they’re still very much coming up to a conjunction on the night that the Perseids are peaking. Early in the morning will be a great time to go looking for shooting stars, as the Andromeda Galaxy will be up along with the Pleiades, while the Persieds are falling. All of these things coming together on one morning makes it a fantastic time to stargaze, especially if you have binoculars. Focusing in with a telescope is more likely to narrow your field of view, which will cause you to miss meteors.

Looking at the constellation of Perseus, I often describe it as a kind of fin shape here, it’s almost triangular but a little bit more curved. With the lines of the constellation, the fin shape becomes a bit more obvious, and it can be seen that a line of stars continues from the tip, creating a longer line with an arm coming off of it, the straighter side of the fin. Perseus himself is really the longer line, with the offshoot being his arm holding the head of Gorgon Medusa. With all of the pictures of the constellations in the sky, you might notice that the radiant of the Perseids looks like it’s in Camelopardalis, the constellation of the Giraffe. Of course, the pictures of the constellations don’t always match with the exact boundaries we use in the modern day. Each section of the sky needs to fit together like a jigsaw puzzle, with no gaps, unlike the artistic representations. Using these boundaries, it looks like the radiant of the Perseids really is in the domain of the constellation Camelopardalis. it is only a minor difference, the radiant is barely across the boundary line, right at the edge of Perseus proper. Perseus is a much more famous constellation than Camelopardalis, a name that comes from “camel-leopard”, a half-camel half-leopard, which is the Latin name for the giraffe. Although it follows the npattern of many mythical creatures, such as the half-goat, half-fish Capricornus, giraffes are a real creature of course. Perseus however was a famous hero in Greek mythology, and his story has even been made into movies. Perseus rescued Andromeda from the Great Whale Cetus, flying on the back of Pegasus and along with Andromeda’s parents, Cassiopeia and Cepheus, these are all constellations in the same region of he sky. I did have a piece, I think last year, talking about the story of these constellations, but it is something I may go over again in the future.

For now, what’s important is that the Perseid are coming up, on the 12th, when the Moon will be out of the sky. They’re a fantastic meteor shower to see, really whether you’re in the city or in the countryside, and perhaps most importantly, there’s no Moon in the sky to interfere this year, which is something that can happen and has happened in the past. Especially if you’ve been let down by these other meteor showers, for example at the end of July. Some sources proclaimed that two meteor showers would be happening both at the same time, or that the Perseids would be crossing over with these other meteor showers, which is technically true. However, when these various sources were telling people that there was a lot meteor showers going on, when really all told the ZHR may have peaked at 35-40, possibly as low as 15, that sets people up for disappointment. It is better to wait for the, potentially, 85 ZHR we can see with the Perseids. If you have been disappointed by other sources, I hope to restore your faith with the honest truth, the Perseids will look good on the 12th, even they might not look that good just a few days before or after. They certainly won’t look good very early in the month, which is something to be prepared for for next year as well. Continuing on to the actual sunrise, Jupiter and Mars get reasonably high in the sky even before the light of the Sun of breaks in. As the sky really brightens we’ve got some famous constellations, Gemini and Orion, coming up as well. Even as most of the stars disappear you might just about see, very faintly, the fin shaped outline of Perseus. Algol, one of the brighter stars in Perseus, almost at the end of the straight edge of the fin, is reasonably bright and will remain visible along with some of the last stars to vanish.

There is of course so much more that could be said about the Perseids, and the comet Swift-Tuttle, C109P/Swift-Tuttle which is the parent body of the Perseids, but I did go over that the last time I spoke about the Persieds. I will most likely talk about them more next year, next August, when they will come back around again as they always do. I do hope that you get a chance to see some of the Perseids this year. As I mentioned in a previous piece about meteor showers, it’s best lie on your back and try and take in as much of the sky as possible and wait until it’s fully dark. You want the Moon to be down, but being closer to morning time isn’t too bad with the Perseids because it brings their radiant higher in the sky. The glow of sunrise of course will block out some meteors. With all that said I still hope you get to see a few of them at least. I also hope that you enjoyed this article, and if you’d like to see more from me, you can help that happen by subscribing to this website and my YouTube channel. Whatever else, I hope I see you back here next time.