Watch the rare sight of a moon’s shadow passing across the face of Saturn. Get the details in the latest episode of our weekly stargazing guide podcast.
Chris: Hello and welcome to Star Diary, the podcast from the makers of BBC Sky at Night Magazine. You can subscribe to the print edition by visiting skyatnightmagazine.com or to our digital edition by visiting iTunes or Google Play.
Ezzy: 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 at in the UK, all times are in GMT. In this episode, we'll be covering the coming week from 8 to 14 January. I'm Ezzy Pearson and I'm joined this week by Paul Money.
Paul: Hello there, Ezzy oh, morning time again to start with. Oh, we'll have to get up for these.
Ezzy: Well, mornings aren't always terrible and there's always usually something great to see in them. So what do we have coming up in this week's night sky?
Paul: Right, well, we begin the week with the morning twilight on 8th, around about 7am.
Now, twilight is getting stronger now, but we have a grand view of the inner planet's Venus and Mercury. Venus is trying to catch up with Mercury, but it's failing. Mercury itself, sort of thing, is quite low down, so you do need an uncluttered horizon. But Venus last week was passing above Antares, several degrees above it, but it was passing above Antares, which is in Scorpius.
But Venus is now in Ophiuchus. But the thing is now on 8th, they're joined by a slim crescent Moon, and that lies right In, Scorpius. In fact, the crescent Moon lies to the right of Antares, forming a lovely triangle with a star and Venus as well. Each joined in with the action, as you might say. A bit extra value for money, as you might say.
So the next morning, so this is now we're talking about 9th. We're looking at a little bit later. You need to give it about 10 minutes later because the Moon as it happens is it's. It's still there, but it's lower. It's the other side of Antares, so you've got to give it time to rise, but it will be quickly overwhelmed by the twilight.
So it's one of these sort of things, you're really on a timer for this. So as soon as you've got Venus and Mercury, forms a triangle below them, sort of an apex of a triangle. This is a very, very slim crescent Moon, so, but you've got to wait for it to rise. But as we always say, don't leave it too late till the sky gets bright and the Sun rises itself.
So we don't want you to damage your eyes, sort of thing. So, but just have a look, but you do need a really uncluttered southeastern horizon to catch that really thin crescent Moon forming this triangle with Venus and Mercury. So that's in the morning sky. But, because the Moon is so slim, it's heading towards new.
Which is great, it'll be new on 11th. So all week, in the evening sky, we've got the winter sky, we've got dark skies! Let's hope we have clear skies as well. It does help. Sort of thing. We have plenty of times in recent months, I have to say it's been pretty awful, whereby, you know, the Moon's been out of the way. You've been thinking absolutely fantastic, and it's been cloudy instead, sort of thing. You know, which is a great shame, because you look forward to these moonless nights, knowing you're going to get the winter sky in full glory.
But it is in full glory. You've got the, actually, if you're looking around about eight o'clock in the evening over in the southeast, you've got Sirius rising. You've got the Milky Way passing Sirius, but he arches up across the sky. So it goes up past, Orion.
So we've got a mighty Orion there. So it goes really between Orion's club and the feet of Gemini.
This is the Milky Way, and then up through Auriga, into Perseus, Cassiopeia. And would you believe it, it still hasn't set, we've still got Cygnus! I mean Cygnus is usually considered a summer constellation, and we're now into the January sort of thing.
But it's one of those things, several parts of Cygnus are actually circumpolar, so they don't actually set as well.
So you've got a lot there, so you haven't just got the giant planets in the evening sky. At the moment, you've got the best time to see the winter sky. Lots of nebulae, lots of deep sky objects. Clusters, a few galaxies as well, sort of thing, as well as our own Milky Way galaxy stretching across the sky.
So there's actually lots to enjoy as long as we've got those clear skies, because there's no moon actually in the way to spoil them. So fingers crossed, Ezzy, we can actually do that.
Ezzy: Yes, and if you want to have a guide to show you what might be worth observing in the winter sky, do pick up a copy of Sky at Night magazine where we have a sky guide which will take you through a binocular and a deep sky tour every single issue of the best things to see. And we also have lots of guides to the winter sky over on our website, skyatnightmagazine.com. So please do have a look at both of those for even more tips and tricks on what's best to observe at this time of year.
Paul: Exactly. I mean, brilliant resources that we've got available.
All week we've got Saturn on view. Now last week, right at the end of the week, we mentioned that the Galilean moons can often have a dance of the planets and they cross the surface of Jupiter. At least the visible surface of Jupiter, and their shadows can do it as well.
But, here's a chance to have one at Saturn.
Now, I mean, I think this is amazing, because this is pretty much... I wouldn't say the total limit for amateur astronomers to see a shadow of a moon on another planet. I'm not quite sure whether anybody's done it with Uranus. It will be quite a challenge, but I think it's been done. But at the moment, it doesn't work at the moment because the angle, the tilt of Uranus as well.
But the tilt of Saturn is getting shallower. The next couple of years, we'll see the rings go edge on. And that means as the moons orbit Saturn, their shadows, they will cross the disk and also the shadows. Now, as it happens, we've actually got an interesting event on 11th. So 11th is of course new Moon for us but it's also a great event. The shadow Dione and Saturn actually crosses the southern hemisphere in the early evening.
I mean the early evening You don't even have to stay up all night for this, you know, you've got an early evening event sort of thing. So you don't have to to wait until the early hours of the morning like sometimes. They usually happen in the early hours and something awkward usually happens as such but this is about 5:30 PM.
Whilst twilight is still fading the shadow will already be close to the centre of the view of the disc of Saturn but it'll get better as the sky gets darker towards six o'clock but the shadow is slowly moving across and it will move off the disk by 6:30. But this is a perfect time to see if you can see.
You will need a telescope and quite a reasonable amount of magnification as well. But Dione will be passing underneath the planet, but its shadow will be crossing and it'll be quite tiny, but to see this little dot. This shadow on the planet's atmosphere, I think will be quite exciting. So I'm looking forward to that.
I'm going to try and video it and see whether we can get some pictures. And again, if anybody does take a picture, please send it up. You know, we love these sort of pictures. Because these are the more rarer ones. Although over the next few years, they'll start to get more and more. We'll see a lot more taking place.
So I'm quite excited by Saturn over the next few years. It's improving its position on the ecliptic. But of course we are going towards ring plane crossing sort of thing in a couple of years and we lose the rings but we gain the moons crossing a planet.
Ezzy: I think that's worth bearing in mind with Saturn. Because people always get a bit sad when the rings close up because, you know, it does tilt backwards and forwards and sometimes when you're looking at it edge on you can't really see the rings as well.
Because that's what Saturn's famous for. But that doesn't mean that there's not still lots of other interesting things that you can see on the planet. Like these shadow transits. So, don't discount Saturn for the next couple of years, it's still always worth a look at that giant planet.
Paul: Well worth it. Now, the next morning, January 12th, yes, we're back to the morning sky as well.
Seven o'clock in the morning, Mercury's at the greatest elongation west, it's about 23.5 degrees away from the Sun, sort of thing. So, when it's on the west side, it's visible in the Morning sky. When it's on the east side, it's visible in the evening sky. Now, Mercury shining up -0.1 magnitude, but from now on, it will gradually now start to drop back towards the solar glare.
This is why Venus won't catch it up. So get them now while they're together because Mercury will very quickly drop out of view. And you won't be able to mistake them to Venus is around about -4.0 magnitude. So a significant difference between the two. In fact, the most. Brightest object, other than the Sun and the Moon, in the sky, has to be said is Venus.
So there we are. So that's on 12th, sort of thing I say, after this Mercury will start to drop back.
Ezzy: Just popped in to say hello and now it's going away again.
Paul: Exactly, yes. It is, it is a bit like that, isn't it, sort of thing, you know, just peeps his head over the horizon, sort of thing. Gives a little wavers for, I mean, if you get the right apparition, the evening apparition, later in the year, sort of thing, you know, the first one, usually in the spring, is usually quite good.
You've got it for around about at least a month, because it lingers. It's all the interplay of the sort of angle of the ecliptic and the position Mercury's along it as well. But we have to wait later on in the year for the morning apparition of Mercury to be really long. But most of the other times, they're quite short, sort of thing.
Because it's down to the angle of the ecliptic itself. But, at least you should be able to see it, But you do need an uncluttered horizon. It's the same old story, sort of thing, If you've got a lot of trees, buildings, or anything like that. You will probably need to find a nice sight, sort of thing, to go out to.
Perhaps if you're on the way to work, there might be a lay by you can pull in, sort of thing, to see it. But, I have to say I've done that a few times, sort of thing, and had my camera with me, and then forgotten the tripod.
Ah! That's usually the case, isn't it? There's always something you forget, sort of thing, you know, that has to do with that.
But I'll tell you what, nowadays, though, you can catch them with the your smartphones handheld, you know, because it's twilight, you can get a good picture like that, so well worth trying that.
Okay, so let's go to the evening sky again now. We're talking about 5:30 in the evening because as we're going into 13 and 14th January, yes, Saturn's in the sky, and we mentioned the transit of the shadow earlier in the month on 11th, but it's now joined by our own Moon. So on 13th, the Moon is to the lower right, quite a few degrees away, but it's just creeping out of the twilight.
You can still enjoy the winter sky, because it's only a slim crescent and it's setting quite quickly. So it is now emerging, sort of thing, so on 13th it's to the lower right of Saturn, about 5:30 but on the next evening, it's directly to Saturn's left. So you've got this lovely... it'll be a gorgeous view, this crescent hanging there, you'll have Earthshine as well.
Remember Earthshine is the light that's bounced off the Earth's bright reflective atmosphere, and it's filling in. I always think of it like the photographers fill in flash, so they often use these parasols don't they, they're brightly lit, to illuminate the other side of the person to make it more even.
This is the same thing. So you'll get the Earthshine, you'll get the crescent, and you'll have Saturn there as well. A great chance for a fantastic picture, I reckon, sort of thing. So, do take a look at that. And that really completes this week's set of events there, Ezzy.
Ezzy: Does sound like we've got a lot of really interesting things this week.
If people at home would like to get to grips with what's happening next week and throughout the rest of the year, do subscribe to the podcast to keep up to date with all of the latest stargazing tips. But thank you very much for taking us through all of that, Paul.
To summarise again, on 8th in the morning twilight, you'll be able to see Venus trying to catch up with Mercury in the constellation of Ophiuchus. They'll be joined by the crescent moon near Antares.
Then moving forward into 9th, the very, very thin crescent moon is going to be moving closer towards Mercury, but it will be overtaken quickly by the dawn. So do be careful that you don't accidentally catch the Sun in any of your optics.
On 11th, we're going to have a new Moon, meaning it's a great time to take advantage of any deep sky observations that you want to do. Perhaps looking at the Milky Way, taking a closer look in Orion. There's lots of nebula, clusters and galaxies that are on display throughout the season, so be sure to pick up a copy of Sky at Night Magazine to keep up to date with the best things to see, or go over to our website, skyatnightmagazine.com.
Again, on 11th, you'll also be able to see a slightly unusual event, as the moon Dione does a shadow transit across the face of the planet Saturn. Definitely one to watch out for there.
On 12th, Mercury is going to be at its greatest western elongation. It'll be quite bright in the night sky, though Venus will be nearby and it will be even brighter.
Then to 13 to 14 January, Saturn is going to be accompanied by the slim crescent Moon as well.
So lots of really interesting things to see in the night sky this week. Thank you very much for joining us and we'll see you here next week. Goodbye.
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 pull out 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.
For more of our podcasts, visit our website at skynightmagazine.com or head to Acast, iTunes or Spotify.
Listen to the next episode of Star Diary 15 to 21 January 2024.
