What's in the night sky in the week of 15 to 21 May, 2023 in our weekly stargazing guide. Jupiter disappears behind the Moon in a daylight occultation, and Mars lines up with Castor and Pollux.


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 15 to 21 May. I'm as you and the magazine's features editor, and I'm joined once again by our reviews editor, Paul Money. Hello, Paul.

Paul Hello there Ezzy. It's good to be back again. Hopefully a few more features and things to look out for this week.

Ezzy Yes, absolutely. So what do we have to look forward to in this week?

Paul Well, I'm going to break with tradition. I mean, we normally do the evening sky first, but no lets start 4AM. in the morning, 15 May. But no, we start the week because we've got Saturn in the east, southeast. You want to be looking for Saturn getting better. Place now is pulling out of the solar glare, although of course, the nights are getting gradually lighter. But Saturn's, bright enough, it doesn't matter too much for that. But way off to its far left, closer to the eastern horizon is the crescent moon. And I love those early morning crescents. They are worth getting up for, to be honest. You do need an uncluttered horizon to be fair. But in the bright morning twilight, this gorgeous crescent Moon. But you've also got the earth shine. It's a great time to get the earthshine on the Moon. So you've got the combination of the sort of gorgeous colours of the morning twilight, the shine and the crescent Moon actually, as well. So but this is so light getting into the last few days or two before we lose the Moon to new and even back into the evening sky. I'm talking of the evening sky. Well, you know what I'm going to say? Yes. And it applies all week. Venus is going to... is still dominating, but with the light skies, you know, we're getting the night skys pulling out. So we're getting the lighter skies. And so, you know, Venus is slowly going to start dropping back. We're going to have it for another couple of months. But, you know, it is still there. So enjoy it while you can sort of thing. And the phase is diminishing. But it is bright -4.3. So pretty bright as such. And in actual fact, this week it lies close and passes Epsilon Geminorum, also known as Mebsuta. If I've got that pronounced right, I never know about pronunciation of these things. It's actually closest on 16th. So look out for thatbecause it's a nice star as well. So is one of those dominant ones of the actual the figure of Castor because of course Gemini is the twins, the two brothers, Castor and [Pollux]. The right hand side is the figure, the stick figure of Castor. And of course, Mebsuta is where you've got I always think it's like the the hip type where the the legs spread out sort of thing. So the bottom of the actual constellation. So Venus is heading towards there. So towards Mebsuta. And on 16th it's quite close to it. Meanwhile, Mars has moved out of Gemini and it moves into Cancer this week. So it does briefly form a straight line with Pollux and Castor. I mean, literally is a real straight line because there's going to be similar brightnesses, it'll be quite prominent so instead of two. And when I look at Gemini to see the twins, I see the two bright stars and they're quite prominent. But now there'll be a third one and that will be Mars. And that again occurs on 16th. But of course, Mars and Venus will be here all week in the evening sky. So even if you don't get a clear sky on that particular night then they'll be hopefully a clear night sometime during the week. We can always hope. Can't we. Now, 17 May, we do swap back to the morning sky. And the thing about this is it is a real challenge. And we always have to do these warnings and quite rightly, too, because I'm looking at a really, really thin crescent moon. 4:30 in the morning. And the reason why I'm looking at it is about 30 minutes before sunrise. So this is why you have to be careful not to overdo it, not to sweep up the Sun. Make sure you stop before the Sun has risen. The point about this is that you've got this very, very thin crescent moon. But at the same time, Jupiter is beginning to emerge out of the solar glare. Its deep in the solar glare at the moment, but you might just be able to pick it out. And having the Moon and then seeing a star. I mean, we know all the stars in that area are sky visible because of the light sky. So if you see a star to the left of the Moon, you've got Jupiter rising. So it's emerging now finally back into the morning sky. So it really is difficult. And you do need an uncluttered, clear horizon. You've got to be very careful because obviously you don't want to leave it too long and times will vary throughout the UK. So the further north the sky will be, light of the sun will rise earlier. So do take that into account we don't want you sweeping up the sun if you are using binoculars. But if you do find the moon, you should better find Jupiter and there'll be a good site in there as well. But do take care. Trying to spot it I like challenges like this, but you have to be careful. You know, you have to use common sense and you do have to be careful when it comes to something like this.

Ezzy As you said, when you are viewing something in the morning sky... because when you're viewing something in the evening sky and it's close to sunset, once the sun's gone down, you know it's not going to come back up again. But with sunrise, you do need to have, you know, build in a fair window, look up exactly when sunrise is going to be in your exact location, and then add some extra time on there as a buffer to be sure that you're not accidentally going to catch something in your optics because we don't want anybody to hurt their eyes.

Paul Exactly. I mean, and look towards the east. The east, the Sun will be well off to the sort of north east side where it rises. So if you concentrate east in that area around there, you should sweep up the Moon. I'd be very, very careful. The will, of course, be the Earthshine again. But I find when you get the moon that low, you've got such a bright sky, it's sort of like starts to fade into the background sky itself. So it'll be interesting to see what your thoughts are on whether you observe the earthshine as well on such a bright sky as well.

Ezzy And also later in the day, on the 17th of May, we do have something... It's not happening in the night sky. It's actually going to happen in the day sky, which is an occultation of Jupiter by the Moon. Now, occultations do happen relatively regularly, but it's not very often that people are looking for one in the daytime sky. But Jupiter is a fairly bright -1.9 and the Moon is a crescent, so you should hopefully be able to see both of them during the day. But obviously if you need to be careful of the sun rising and accidentally catching it in your binoculars, you need to be doubly careful when the Sun is up and high in the sky. So this occultation is going to occur between 11:30am to 5:30pm BST. But if you're in the UK, it's only going to be visible if you're in the very north. So if you are in most of Scotland and the northernmost tip of Ireland will be able to see this occultation. If you're on that border though, you might see what's known as... You might be in what's known as the graze zone, which is where the planet appears to just brush past the Moon rather than disappearing behind it. But for those of us in England or Wales or most of Ireland, then unfortunately you will just see Jupiter passing very close to the Moon instead of disappearing behind it.

Paul But I'd still be excited by that.

Ezzy I know I'm still going to be on the lookout for it. It will be relatively easy to see in the day sky. It will be due south and about 47º in altitude. So hopefully, even if you're at work, it might be above all of the buildings, possibly if you're in a city centre with a bunch of high rises, you might have to be a bit more careful about where you are trying to see this. Do you be careful, though, because the Sun is going to be 27º away. The best way to avoid catching the sun in this case is to try to find a spot where you can see the Moon and Jupiter. But you're in a shadow because if you're in a shadow, then you're not accidentally going to get the Sun coming through your optics. Of course. Do be careful even then, make sure you've got somebody who's paying attention to where the shadows are because you don't want to get caught up in the moment looking through your eyepiece and then not notice that the sun has moved. Because that does happen. So, again, be careful of the sun, but maybe there might be some people out there who will get the chance to see the occultation of Jupiter in the daytime.

Paul Now, New moon, of course, takes place. And then I think that on 19 May, I'm getting confused with it on in back in April, when, of course, there was an eclipse. Lots of friends who went out to Australia to see that sort of thing. So one of those things. I wish... I would love to do that again, see an eclipse of the sun. But I've got a long time to wait before it happens in the UK. Very long time to wait. But we end the week with the moon is due on 19th and emerges back into the evening twilight. So he's done a complete circuit round this month. So then we're heading back into Venus territory as I call it at the moment, but it is in the twilight it will be a crescent again. So again you get a second chance to have a look at the actual evening twilight sort of thing and the the actual earthshine taking place as well on the Moon. And interestingly enough we've lost the Pleiades. Sadly, we will have lost the Pleiades. But the Moon, Venus, Mars and now the Beehive Cluster forms nearly a straight line. So you go from. The moon, low down is on the north west to Venus, in the west northwest to Mars. And the the Beehive Cluster in the west itself as well. So that Mars is in Cancer is heading it looks like its heading for that cluster. So. Be well worth keeping an eye on that and then is trying to catch it up, but it's not going to succeed. But it does form an interesting triangle, a very long, isosceles triangle with Castor and Pollux. So Venus is the apex pointing down towards the horizon itself. So there. You want to be looking around about 10:00pm now. You notice other times of gradually got later. So then, because the skies are getting lighter as we head towards the summer skies. So, you know, it's well worth it. But I think we got three... We've technical got four planetary bodies because you've got to include the Earth as well. But we've got the crescent Moon, we've got Venus and we've got Mars, and then we've got the cluster as well. The Beehive Cluster as well to have a view at. So not quite as many events this week, but that's how it goes. You know, it's one of those things of the night sky and sometimes, you know, where we have a bit of a scarcity of planets as at the moment we've only really got... I mean, three that are easily visible. So we've got Venus, Mars and Saturn. But, you know, from next week onwards, without Jupiter, better. So more to look forward to.

Ezzy Absolutely. So in summary, throughout the week, Venus is going to be in the constellation of Gemini in the evening sky. On 15th in the morning, Saturn will be in Aquarius. Also, a good time to look out for some Earthshine on the Moon. The 16th Mars will be forming a line with the stars Castor and Pollux in Gemini. The 17th just before sunrise. Jupiter is going to start emerging from the solar glare. But do be careful that you don't accidentally catch the light of the Sun through your optics. And then on 21 May, Venus and Mars will be visible in the twilight as the twilight is fading. So lots there to see throughout the week.

Ezzy Pearson If you want to keep up to date with all of the latest stargazing highlights, do be sure to subscribe to the Star Diary podcast and we hope to see you all here next week. 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. Well, we have a 16 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 a 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.