Saturn’s moon Dione casts its shadow across the ringed planet this week. Find out how to see the sight for yourself by listening to this week’s episode of Star Diary, the podcast from the makers of BBC Sky at Night Magazine.
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Chris Bramley: Hello and welcome to Star Diary, the podcast from the makers of BBC Sky at Night Magazine. You can subscribe to the digital edition of the magazine by visiting iTunes, Google Play, or Apple News, or to the print edition by visiting skyatnightmagazine.com.
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 in the UK, all times are in BST. In this episode, we'll be covering the coming week from 29 July to 4 August. I'm Ezzy Pearson, the magazine's features editor, and I'm joined today by Katrin Raynor an astronomer and astronomy writer.
Hello, Katrin.
Katrin Raynor: Hi, Ezzy. How are you doing?
Ezzy: I'm doing well. I'm excited to hear what we've got coming up in this week's night sky. Apparently it's going to be a bit of a busy one.
Listen to last week's episode, Taurus the Bull gains another eye (Star Diary, 22 to 28 July)
Katrin: It's all about the Moon, Mars and Jupiter this week, but you will need to get up early to see them as they are only visible in the morning sky.
We also have some great planetary moon transits that will be well worth photographing. And, as usual, noctilucent cloud season still ongoing, but be mindful, their presence is going to start to tail off as we enter August.
I'll kick off with NLCs, noctilucent clouds. They have been a main feature of the Star Diary for quite some weeks now. Well, since June, and as I said at the beginning, you know, we're going to see them into August, but they are going to start to dwindle now .
So just a reminder, you will need to look to the northwest horizon around 90 to 120 minutes after sunset, or a similar time towards the northeast before sunrise.
Use your eyes. You don't need any equipment and they're going to look blue white, almost electric in the twilight sky. And as we have said in previous weeks, you know, take to the internet to look at some images just to familiarize yourself with what you're going to be looking out for.
And I promise I'll stop talking about them soon.
Ezzy: We're entering the end of the season, so it's your last chance... well, one of your last chances to go out and see them. So definitely try and get that if you haven't already.
Katrin: And it is important, isn't it, I think. It's one of those things that you only see for a couple of months in a year and during the lighter evenings when there isn't too much else to see if it is too bright NLCs do kind of give you that fix, don't they, of seeing something in the sky.
We'll stop talking about them soon. They'll be old news.
So the Moon is waning all this week and its position in the morning sky will create some lovely observing and photography opportunities with the planets.
There's going to be a new Moon on 4 August, which will be a welcome respite, I think, for some observers who already struggle to observe in the lighter nights of summer and want to get some deep sky observing under their belt.
So Solar System wise, on 29th as 29% lit waning crescent Moon rises, that's gonna be quite easy to remember, it's 29% on 29th.
Ezzy: It's nice when they do that.
Katrin: Yes.
Ezzy: It's very considerate of the universe.
Katrin: Yes. It's lovely. So the waning crescent Moon is going to sit 1.5º east southeast of the star cluster, the Pleiades and as the morning creeps onwards Mars will rise just after 1:00AM and Jupiter will follow shortly afterwards at 1:30AM.
So we have spoken about that the past couple of weeks really, haven't we? Like what's happening in Taurus. That seems to be where a lot of the planets are positioned at the moment. And yes, it's just lovely section of the sky to look at.
Ezzy: There is a lot going on in Taurus.
Katrin: Yeah, there's so much, isn't there?
I do enjoy observing Taurus and as well I think it's a great constellation to observe because you can see so much with just your naked eye or binoculars, big telescope, whatever. You know, you can see star clusters with your naked eye, you can see variable stars, so it's a great constellation.
So on 30th the Pleiades star cluster rises at 12:07AM and is shortly followed by the waning moon 8 minutes later and if you have a clear northeastern horizon this is going to be a lovely sight to see.
The Delta Aquarid meteor shower peaks today And you're probably only going to see around 16 to 20 per hour. As we've mentioned previously, you know, these are best seen in the Southern Hemisphere and they appear low on the horizon for us in the northern hemisphere. So you would need a good unobstructed view and dark skies.
To locate the radiant point or the point from which the meteors appear to come from, find in the constellation of Aquarius the faint star called Skat. So you might need to use an app or a star guide to help you locate this star and the radiance is going to rise mid evening and be highest in the sky at 2:00AM.
Ezzy: So the radiant- just in case people aren't familiar with meteor shower nomenclature- that's the point where all of the meteors appear to be coming from. So it's basically the direction of where the Earth is heading. So that's where the Earth is plowing through this, this debris field that causes meteors.
It's not usually the best place to see it. You want to actually look slightly away from the radiant because as they're streaking, they're streaking away from that, that's where you want to look is slightly away from it.
Katrin: Yes, that's a good point to raise actually, thank you.
On the 31st the Moon is now a very thin crescent, only 20% illuminated and rises just before 1:00AM.
Mars rises around 10 minutes later with Jupiter not far behind, so the trio of Mars, Jupiter and Aldebaran is going to form a triangle in the morning sky. It's another fantastic naked eye or photography observing opportunity for those of you who are up in the early hours.
And Saturn's going to be at its highest point in the sky on 31st in the south, located to the east of the constellation Aquarius. So the ringed planet will rise just before 10:30PM, but the best time to view will probably be after 3:00AM.
And if you're out looking at Saturn, now is a good time to view Neptune. It is slightly higher in the sky than Saturn and to the east of Saturn near to the constellation of Pisces. So now Neptune is going to be a magnitude of +7.8, so you are going to need binoculars or a telescope to see this planet.
Ezzy: We do quite often talk about planets being better to see when they're high in the sky, but we don't actually often say why. So that's partly because then they're away from the horizon so you're less likely to have trees and things in the way.
But it also, the air is a bit more stable higher up. Close to the horizon it tends to make things a bit wobbly, which can make it a bit difficult to focus on these planets sometimes.
Katrin: Yes. And sometimes you can tell, can't you, when you're looking through a telescope, it does appear to be, like you say, wobbling.
It's not quite a clear image of the object that you're hoping to see.
Ezzy: I've seen some where it's, you know, it's like a mirage. It's just wobbling all over the place. And it's exactly like that. It's usually not that bad.
Katrin: I like that. A mirage, that's a nice way of describing it, I think.
Ezzy: The same effect, really. It's the, the air bending the light as it's coming through and affecting how we see it.
Katrin: Yeah, so it's important to consider, I think, isn't it, when you're looking through your telescope wondering what's going on. It's not your telescope, it is probably just the atmosphere interfering.
So we also have on 31st Ceres, a main belt asteroid smack bang in the middle of The Teapot asterism in the constellation of Sagittarius.
And there's no Moon to interfere with observing it. So Ceres is going to rise at 8:20PM and set just after 2:00AM. It's going to be a magnitude of +7.83. So you're not going to see with the naked eye a small pair of binoculars or a telescope, you should be able to spot it. But the problem with asteroids is you kind of really have to know what you're looking for because they do look like star like points of light, don't they? So yeah, you're going to need some kind of additional help, I think, to help you locate any asteroid that you want to see that's visible in the sky.
Ezzy: I think one of the best ways is if you come back to it night after night and you can slowly see Ceres making its progress through the teapot, which is still a weird sentence to say. And then you'll get more to grips with what the stars are within that part of the sky to begin with, and you can hopefully see this one thing starting to make its progress along the way.
Katrin: Yeah, it's a good way of knowing that you have actually observed it and plotting it is, I think we said before, making a little flick book would be quite cool, wouldn't it, of your observations. You can just see it moving.
So on 1 August, you know, we're going to kick a new month off with an 11% lit waning Moon. It's rising just after 1:30AM, by which point Mars and Jupiter will already be visible in the morning sky.
And as the Moon rises higher, an open star cluster M35 in the constellation of Gemini will lie just below. So M35 is also known as a Shoebuckle Cluster and is a naked eye target from dark sky areas. But as usual its name doesn't really match with what you might see. So don't expect to see a shoebuckle.
Ezzy: Doesn't look like a giant shoe floating in the sky?
Katrin: No, not at all. I would be interested to know, I suppose, where that name came from and who came up with it.
Ezzy: It might be one of those things that it was, at the time it was named, shoe buckles looked very different to what they look like today.
Katrin: Oh, yeah, that's true. Yeah.
Ezzy: Which is another thing to think about when these names is, did the thing that it's named after look the same then as it does now?
Katrin: Yeah, I mean, do we get buckled shoes anymore? I just don't know.
Ezzy: Occasionally, but not very often. It's more a fashion choice.
Katrin: Yeah, the Velcro cluster doesn't quite have the same ring to it, does it?
Ezzy: No, it's not quite as romantic.
Katrin: So the Shoebuckle Cluster will shine at a magnitude of +5.2. And if you grab a pair of binoculars and take a look, it's going to reveal many more stars. And we also have another open star cluster very close to M35. It's got the snappy name of NGC 2158. And this open star cluster looks much more compact in its appearance.
Compared to M35, so going to be a great chance to see two open star clusters very close together.
Now on 2nd, we have another transit of two of Jupiter's moon shadows to look out for in the early hours of the morning. So Io and Ganymede's shadows will transit the gas giant between 12:23AM and just after 1:45AM.
If you tuned in a few weeks ago, I talked about the light and colour of the four moons. They blend in really well with the light and colour of Jupiter. So seeing the moons themselves, it's going to be a challenge in front of Jupiter itself. But the shadows of the moons are, you know, really easy to see on Jupiter because we see them as a dark point against the bright planet.
So yeah, you're going to need high power binoculars or a telescope to see this. Again, grab your DSLR if you want to take some photographs and share them with us. It'd be great to see these transits, wouldn't it?
Ezzy: Absolutely. Uh, we always love to see your images and your sketches maybe if you've done any or just write in to tell us what you've seen. You can contact us at. contactus@skyatnightmagazine.com. We'd always love to hear from you.
Katrin: And on the 4th, we've got another moon transit to enjoy, but this time it's on Saturn. So Saturn has 146 moons at the time of recording with confirmed orbits. And in the early hours, Saturn's fourth largest moon, Dion, will transit the planet just before 12:30AM and continue until 2:25AM. So you're going to need a larger telescope to see this transit. But again, I'm going to try and get outside and see this and I can tick more things off my astronomy bucket list this year.
Ezzy: Absolutely. It's always good to have
the list that you're slowly ticking down. And as you improve in your journey, you add more things on more challenging things that require bigger, beefier, more expensive telescopes.
Katrin: Bucket list goes to space. Yeah.
Ezzy: Well, Saturn seems to have no shortage of moons to be able to see. I remember when there was less than 60. So now there's 146.
Katrin: The list is getting longer and longer. I think, okay, what we'll do is next time we record, I'm going to ask you to recite all of them from memory.
Ezzy: All of them? Because I think some of them are called, like Saturn moon 47B and things like that.
Not all of them have exciting names like Enceladus and Titan and things like that. Most of the moons of the Solar System are named after, you know, Greek gods, Shakespearean heroes and heroines. That's around Uranus, I believe.
Katrin: Titania? I believe
Ezzy: Yeah, Titania, Oberon, all of those. The entire cast of A Midsummer Night's Dream can be found around Uranus.
Katrin: Yeah, they're not memorable some of the moon names, or like we've said in the past, you know, planets or star systems, just, I don't know how anyone's supposed to remember the long chain of numbers.
Ezzy: It's a problem that now we're finding so many of them. We found 146 moons around Saturn and we're finding, I think at last count, it's close to 6, 000 exoplanets and it's just, you can't keep up with it.
So the exciting ones get to have fun nicknames, but for the rest of them, we'll have to stick to chains of random letters and numbers.
But hopefully there's still a lot of things to see slightly closer to home.
And if our listeners at home would like to keep up to date with what's going on in the night sky throughout the weeks and going forwards, please do subscribe to the podcast and we'll be back here next week.
But just to summarise this week again.
It's still noctilucent cloud season but it is beginning to come to its end so make sure you get out and see those if you can.
The Moon is waning all week and there will be a new Moon on 4 August.
On 29 July, a 29% lit waning crescent Moon lies in the Pleiades.
On that same night, Mars will rise just after 1:00AM and Jupiter will follow shortly afterwards at 1:30AM.
The Delta Aquariid meteor shower peaks on 30th. It's not the most prolific shower and is best seen in the southern hemisphere, but it's still worth getting out there and keeping an eye out whilst you're out observing for other things.
On 31st, keep an eye out for Mars, jupiter and Aldebaran positioned in the early morning sky forming a triangle.
Saturn will be at its highest position in the southern sky that night as well. And Ceres, a main belt asteroid will be in The Teapot asterism in Sagittarius, all on 31 July.
Moving into August on 1 August, the thin crescent Moon lies above open star cluster M35 in Gemini.
On 2nd, another transit of two of Jupiter's moons cast their shadow onto the planet's surface.
And finally, on 4th, another planetary moon transit happens, but this time it's Saturn. The moon Dione transits Saturn after midnight, and that transit will last for a couple of hours.
So lots of things to look up for and get to grips with and hopefully we'll see you all back here next week.
See you soon.
If you want to find out even more spectacular sights that will be gracing the night sky this month, be sure to pick up a copy of BBC Sky at Night magazine, where we have a 16 page pullout sky guide with a full overview of everything worth looking up for throughout the whole month. 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 detailed star charts to help you track your way across the night sky.
From all of us here at BBC Sky at Night Magazine, goodbye.
Chris: Thank you for listening to this episode of the Star Diary podcast from the makers of BBC Sky at Night Magazine, which was edited by Lewis Dobbs.
For more of our podcasts, visit our website at skyatnightmagazine.com/podcasts or head to Spotify, iTunes, or your favourite podcast player.
