What's in the night sky in the week of 22 to 28 May, 2023 in our weekly stargazing guide. Watch out for noctilucent clouds, and Mars and Venus continue to dominate the evening sky in this week’s stargazing guide.


Chris Bramley Hello and welcome to Star Diary, the podcast from the makers of BBC Sky at Night Magazine. You can subscribe to the print edition of the magazine by visiting www.skyatnightmagazine.com or digital edition by visiting on iTunes or Google Play.

Ezzy Pearson Greetings, listeners, and welcome to Star Diary, A weekly guide to the best things to see in the northern hemisphere's night sky. As we are based here in the UK all times are in BST. In this episode we'll be covering the coming week from 22 to 28 May. I'm Ezzy Pearson, the magazine's features editor, and I'm joined this week by reviews editor Paul Money. Hello, Paul.

Paul Hello, Ezzy. Looking forward to some nice, exciting events now.

Ezzy Oh, do we have anything good to look forward to this week? Please do share.

Paul Well, there's all sorts going on. I think we should start off with the fact that this is the beginning, really, of the noctilucent clouds season. And so, you know, these are nice shining clouds that you can see. And they sort of... I always think of them as replacement for aurora in the spring and autumn sky.

Ezzy I can see why.

Paul I mean, I, I've seen aurora in the summer, but they are rare. It has to be really good display to be seen so well against the bright night sky. But I have actually seen them in July, which was a bit of a shock, I can tell you.

Ezzy Aurora, are happening year round. It's just in the winter. They are happening at the time when the sky is properly dark and you can actually see them. So yeah, it's you do need to have a very bright aurora to be able to see them in the twilight.

Paul I know it's quite something, but yeah, these are, these are quite bright silvery blue clouds in the evening time. You want to be looking about an hour to an hour and a half after sunset and look towards the north-western horizon. And although the skies will be bright, you know, you do tend to... If you see these shimmering clouds. Now, bear in mind, if there's the moon up, then the moon will illuminate ordinary clouds. But these are quite low down unless you get a really extensive display. Now, you know, if you get a big display, it can go mad. But I've had displays that have lasted 10 minutes and gone. They are a bit like aurora in that respect. You know, they can sort of shimmer and they can just fade and is down to ice particles. The ice forms around particles of dust that we think come from meteors entering the atmosphere. So the ice forming around these particles and they're so high up anywhere from 50... they're about 50 miles or say about 82 kilometres in new money. And so, you know, they're fairly high so they can still see the Sun. So that's why we still see these shining. And what I tend to find is that normal clouds by then should be low enough that if there's no Moon around to illuminate the clouds, they should appear dark. And you can actually see those sometimes against the noctilucent clouds. So there's often that subtle little structure in them. And they can move quick. They can be quite slow at times but you can have fast moving noctilucent clouds like wisp developing and spreading across that northwestern sky and technically through the night it gradually moves northwards. And then in the morning you see them in the morning sky towards the north east. All right, about say so, an hour, an hour and a half before sunrise. If it gets too close to sunrise, the brightness of the sky completely overwhelms them. But that can be very pretty. And they say they're they're noctilucent because they're night shining clouds. That's what it actually means. So well worth looking out for. And this will go on until about August, probably about mid-August, although I have seen a display once in September. But that was a very rare occurrence. I think I've only ever seen the one I've only ever heard of a couple. So but as a rule, we tend to think of August as being the main cut-off. So that's one thing to start looking out for from now on.

Ezzy I think because it's noctilucent clouds that. It's the sunlight reflecting off of ice crystals and a layer of the upper atmosphere. Exactly which one escapes me at the moment.

Paul Mesosphere, if I remember rightly.

Ezzy Mesosphere. Thank you Paul . And there's all kinds of things that affect how much ice crystals there. One is, is the temperature. So because of the weird way that the atmosphere works, the like the mesosphere and the ground sort of go opposite each other. So the warmer it is on the ground, the cooler it is in the mesosphere and vice versa. So that's kind of like when it's cold in the winter, that's why you don't get them up there as much during the winter, which is it's one of those things that kind of... There's so much in astronomy that's backwards.

Paul Well, like if you.

Ezzy If you go backwards.

Paul You can see the ones in Australia when it's our winter time because it's summer for them so they get the displays then. And places like Spaceweather.com are very good for keeping an eye on these. Because they have specific charts which actually show the activity at the time, so it's quite interesting to follow that. So they're usually a good guide, both the aurora to be honest, and the noctilucent clouds, so as well as a host of other information. But of course always come to Sky Night Magazine first. It's got to come to us first.

Ezzy But we do of course, have lots of guides about how to see the noctilucent clouds and how to know what to look for. So if you want to just take a look at what you're looking for, do head over to www.skyatnightmagazine.com And I will put a link in the show notes below as well.

Paul See we're so obliging aren't we? moving on then. We are in late May. Now May 23. Now, this is a daylight thing. It's not an occultation as such, but I would think is fascinating because the moon, even as a crescent, usually can pick it up in daylight. It surprises a lot of people you can see it in daylight. You can see it and we're looking around about, say, about midday, because if you can look at the crescent moon and find it at midday... this is the 23 May. Look with binoculars. Don't go too far to one side because you obviously get too close to the sun. But look to the lower right of the Moon. And if you see a dot, a light, that's Venus. In daylight. So now very rarely I have I've seen a couple of times in daylight without the Moon being there. But conditions really do have to be... Like you said, about the atmosphere. The sky has to be really rich, blue with no haze whatsoever. You get the slightest eyes, it's going to wipe it out. But if you've got a really rich blue sky, then that pinprick of light, you've got good eyesight actually pick out quite well. So. But binoculars will make it easier. So have a search round the moon on the 23 May, around about midday, look slightly to the lower right. And you should see this light, which is the planet Venus, in daylight. And the fact that the Moon is next to it gives you a handy guide. It is Moon. It's annoying to some, but it is very useful at other times as well.

Ezzy It is quite good for finding your way around the night sky. As you usually say, if you can't find the Moon. Probably not a great day to do astronomy unless it's a new moon.

Paul Yeah, that's true. And then you hope for a solar eclipse sort of thing. But it needs to be schedule one if there's an unscheduled solar eclipse. Worry.

Ezzy We have bigger problems.

Paul Yes, exactly. Leo, you're watching a movie without realising it. Now, the next evening, we're looking towards sunlight, keeping to the evening sky for most of this session. And so May the 24th, around about 10:00,10 p.m.. Look for... Venus and Mars have been dominating the evening skies now for quite a long time and Venus is slowly catching up with Mars. But for reasons we can't go into at the moment, it will not catch it will not catch up with it this time. And so they'll always keep a separation, but they will close the gap. And on the 24th, we mentioned the Moon is close to Venus on 23rd, the day, well it's actually a bull on Mars. So on 24th, around about 10:00. So Venus is in Gemini. It'll form a bit of a triangle with Castor and Pollux, as well as sort of thing hanging down below them. Mars is off to their upper left and the moon will be again.... The moon is a guy to pick up on the moon, give up. Take a bundle there, obviously. But, you know. So probably watch out for bats flying around at night, because that's a nice thing. I like that. Okay. I sometimes like little additions to my observing session when I get visited by either cats, hedgehogs or bats. So they just had a little bit observing session. But yeah, the moon is a thick crescent now and above Mars for this particular time. And to their left you've also got the cluster Messier 44, the Beehive cluster. So you'll be able to weep that up with binoculars as well. And I mention that because next week we will actually find Mars creeping up and closing in and going into the cluster itself. So that's something to look forward to.

Ezzy Preview for next week.

Paul We jump to May 26th and 27th and the moon has gone past, the beehive cluster has gone past. In actual fact, the constellation Cancer now lies just to the right, in actual fact of Eta Leonis. And I mention that because the brightest star below to the left is actually Regulus. That's the main star of Leo the Lion. And so you'll notice the moon and Regulus is much brighter than Eta. So, you know, that's a key sort of thing. You'll see these bright stars, so the bright star will be to the lower left. But if you've binoculars, you will see this sort of star to the left of the Moon and the Moon creep closer to it. I don't occult it. It goes under at this time. And then the next night it's actually first quarter. So we the moon, obviously this first quarter sort of thing, you know, the moon is half phase. Again, astronomy is not and it's always a half illuminated moon. But what we mean, he's going to go through its orbit from new thing so its first quarter and it'll light to the left hand side, the upper left of Regulus this time. But there is something else in this region which is just picking up. But if you've not got a minor planet, an asteroid for another word, sort of thing, the dwarf planet now in particular because it got converted because Ceres, which was the first minor planet to be discovered. Ceres is quite close to the star, Denebola, which is the point, the tip, the far left of Leo the lion. So it's worth having a look around there. And if you make a little drawing without cheating and using software to identify which one is. Make a drawing. If you get a couple of nights, the one that's moved will be Ceres. That's how you know these things is great for photographers as well. I've got a friend of mine doing a sequence at the moment sort of thing whereby he's taken a sequence showing it moving past this particular star because its quite close. It's handy when again like the moon guides us to some things when there's a bright star and it guide you on to a minor planet, or in this case a dwarf planet as well. Now you won't mistake them because Denebola is magnitude +2.1 and Ceres is +8.1. So a significantly fainter minor world there. So we get to the end of this particular week and that's May 28. And we now I'm sorry, but it's the morning sky. Yes. We got to have some things in the mornings, haven't we?? We can't have it all in the evening sky, for heaven's sake. And we're actually looking out because we've got three planets. One is just emerging and we're looking at around about 3:30, 3:40 in the morning. In the morning twilight, you've got Saturn - that's in Aquarius –you've got Neptune. Now, you'll need binoculars or a telescope for Neptune. It Is a lot fainter. And then if you keep watching over towards the well, the east north arising, you'll see a bright planet, a bright dot slowly creep up from the horizon. And that's the return of Jupiter. The return of the king. Jupiter. So, yes, Jupiter is beginning to come back. And it,being bright, you get it earlier than some of the fainter planets like Neptune and even Saturn, really. So Jupiter is actually back. But to say around about 3:30, 3:40. About 3:40 is when Jupiter rises. But do bear in mind, wherever you are in the United Kingdom, you will find that will vary. So further north you'll have to wait a little bit later. So you see the problem sort of thing. You have to adjust your time. So we tend to do these timings for the middle of the country, trying to be fair to everybody.

Ezzy Yeah, definitely. If so, if there's ever a specific time for anything astronomical, whether that's sunrise or a moon rise or when an occultation is going to happen, it always pays to double check exactly when that's going to happen and also get set up a couple of minutes early just in case your watch is a bit off. But yes, it certainly sounds like there are lots of fascinating things to see in the night sky. And if you want to keep up to date with all of the latest stargazing tips, please do subscribe to the podcast. So in summary, this week, noctilucent cloud season begins. So keep an eye out for those night shining clouds. Then on 23 May, the crescent moon will be near the planet Venus. On 24 the Moon and Mars will be near M44. The Beehive cluster moving on to the 26 and 27, the Moon will pass by Eta Leonis and Regulus and the dwarf planet Ceres will pass by Denebola on the tail of Leo. Then on 28th, Saturn and Neptune will be in the morning sky, and you might even be able to catch a glimpse of Jupiter as it makes its return. So thank you very much for taking the time to talk to us today Paul.

Paul That's a pleasure.

Ezzy And thank you very much, everybody, at home for listening. If you want to find out even more spectacular sites that will be gracing the night sky throughout the month, be sure to pick up a copy of BBC Sky at Night magazine, where we have a six page pull out sky guide with a full overview of everything worth looking out for. Whether you like to look at the moon, the planets, or the deep sky, whether you use binoculars, telescopes or neither, our sky guide has got you covered with the detailed star charts to help you track your way across the night sky. From all of us here at BBC Sky and Night Magazine. Goodbye.


Chris Bramley Thank you for listening to this episode of Star Diary, the podcast from the makers of BBC Sky at Night magazine. For more of our podcasts, visit our website at www.skyatnightmagazine.com or head to aCast, iTunes or Spotify.


Elizabeth Pearson
Ezzy PearsonScience journalist

Ezzy Pearson is the Features Editor of BBC Sky at Night Magazine. Her first book about the history of robotic planetary landers is out now from The History Press.