Mercury reaches greatest elongation this week, while Jupiter will be bracketed by its moons. Find out how to see both of them in our weekly stargazing podcast, Star Diary.
Chris: 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: 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 GMT. In this episode, we’ll be covering the coming week from 18 to 24 March. I’m Ezzy Pearson, and I’m joined this week by Mary McIntyre.
Hello, Mary!
Mary: Hello!
Ezzy: So, what do we have going on in our night skies this week?
Mary: Well, in terms of planets, Mercury is the shining star, really, because it’s going to reach greatest elongation on 24 March, so that is where it’s at its greatest western point away from the Sun.
So it’s going to be visible in the west after sunset and it’s not setting until 90 minutes or two hours after the Sun as the week goes on. So it’s the best opportunity that we’ve had so far this year to look at Mercury.
It is going to fade in magnitude but when it’s at kind of magnitude +0.1 it’s still pretty easy to spot even with the naked eye and even more so with binoculars.
Though if you do have kind of strong binoculars or a telescope, if you was looking at Mercury last week you would see that it had a gibbous phase like the Moon does. But as we move through the next couple of weeks that phase is going to change down to a crescent phase and it was Galileo looking at these phases that made him realise that the heliocentric theory had to be correct, that there’s no way that these planets could exhibit these phases if they were in orbit around Earth.
So it’s really fun to actually see the phases of Mercury and people often forget that Mercury does exhibit phases as well. So it’s really good to look for that if you are looking for Mercury.
Ezzy: Mercury is a bit of a tricky one because it is so close to the Sun and it moves very quickly.
Mary: Yes. It’s one of the reasons why they, as you said, they knew it was in close to the sun is because it moves across the size.
Ezzy: In fact, that’s why it’s called Mercury, because he was the fleet footed god zipping around the sky.
Mary: He does zoom around. We’re starting to lose Jupiter a little bit now. He’s slipping lower into the dusk sky. So if you go out on 18 March at 20:15 Jupiter’s only 20 degrees above the horizon and is now setting at 22:30.
But on 20 March, it’s a really good time to go and have a look at Jupiter because the Great Red Spot is going to be in transit and at the time that the Great Red Spot is bang in the middle at 19:00, Jupiter is going to be 30 degrees above the horizon but what makes this really special is that the Galilean moons are completely evenly spaced either side, to each side. So as you look at Jupiter, you’ll have Callisto and Europa on one side, Jupiter in the middle, Io and Ganymede on the other, and they are perfectly spaced around Jupiter, with the Great Red Spot bang in the middle. So it’s like the most perfect alignment to actually look at.
Uranus is still to the upper left of Jupiter, about 9.5 degrees to the left of Jupiter, and is setting at 23:00 so you still have a chance this week to have a look for Uranus.
Moving on to the Moon, we’ve got the Moon moving from first quarter through to full Moon, so we have a full Moon on 25th.
Again, there are a couple of really nice clair obscure effects to look for. On 18 March at 23:00 we have the Eyes of Clavius. Now Clavius is one of the biggest craters on the lunar near side and it has two smaller craters on its inside and the light just catches the rims of those craters before the floor does and it looks like a pair of eyes looking out at you.
So that’s a really fun one to look for. On 20 March we have the Jeweled Handle or Sinus Iridium and that is where the edge of Sinus Iridum is catching the sunlight and really shines up brightly against the slightly darker maria surface on the basin of Sinus Iridum. So it’s just absolutely beautiful to look at and it is sometimes called the Jeweled Handle because it does look like the handle of a sickle and it is really lovely to look at.
Another clair obscure effect is Cassini’s Moon Maiden, and this is actually visible for a few days. Most clair obscure effects are very time critical, but if you look at the bottom edge of Sinus Iridum, when you look at it through a telescope, everything is upside down. And when Cassini was looking at the Moon, he saw this as the side profile of a lady with long flowing hair, so he named it Cassini’s Moon Maiden after Genevieve, who was his wife.
And I hadn’t actually seen this clair obscure effect until last year and realized I photographed it hundreds of times and hadn’t noticed that that’s what it was. Because when you see it the right way up it doesn’t look like a lady but when you look at it upside down it really does so that’s a really fun one to try to look for.
We do have a couple of lunar conjunctions as well, so on 20 March the 77% Moon is going to be only 5.5 degrees to the right of the Beehive Cluster, so that will be lovely to see. And on 21 and 22 March the 91% Moon is going to be very close to Regulus, so that’s going to be kind of best viewed in the early hours of the morning and it’s going to be fairly close to Regulus.
On 24th, the Moon is going to rise almost full and that night there is actually a penumbral eclipse. So the penumbral eclipse is kind of hard to see, it’s just like a very slight dimming because the Moon is just passing into the penumbral shadow of the Earth. We’re not going to see any more of the eclipse from the UK and we’re only going to see a hint of that at about 4:55 in the morning.
So not one I’m probably going to set my alarm and get out of bed for, because I don’t do mornings, but it is always fun to see that and just being aware of again, like Earth is casting a massive shadow out into space. And when the Moon passes through that, it dims the light on the Moon. So even though a penumbral eclipse isn’t a wow, when you look at pictures of it, it does kind of give you a sense again of that movement of the Solar System and the interplay of all the shadows in the Solar System.
Ezzy: Yes. I think people, if you are interested in seeing an eclipse, there is a much bigger and better one that is on its way in the next couple of weeks. On 8 April, an eclipse will be passing across the entirety of the continental United States. It’ll be visible across North America.
You will be able to see some of a partial in the UK. It’ll be very, very slim, but you should be able to see something. But if you are looking forward to an eclipse, that is probably going to be the one that you’re going to pay attention to a bit more. There will be other lunar eclipses, I’m sure, in the UK that are going to be much better. But…
Mary: They are very common.
The great thing when the eclipse does happen properly, there’s always somebody live streaming it from somewhere so you can still enjoy it thanks to the internet.
Ezzy: Somebody will do it and you won’t have to get up at four o’clock in the morning.
Mary: No.
I would talk about Comet 12P/Pons-Brooks again because it’s still moving towards perihelion and is kind of slowly brightening. Although what magnitude it will be at this point, who knows?
Probably somewhere around mag +6.0 but this outbursts all the time so we don’t know. But what’s interesting is that it’s going to be in conjunction with Messier 33, the Triangulum Galaxy. That is a galaxy that is fairly easy to spot in binoculars, so just have a look for that, 3 degrees away from M33 on 23 March.
Ezzy: Well, thank you very much for taking the time to go through all of those things with us, Mary. It sounds like there is a lot of really interesting things to see in the night sky this week, so thank you very much.
Mary: Thank you.
Ezzy: And if our listeners would like to keep up to date with all of the stargazing highlights, please do subscribe to the podcast and we will be back here next week.
In the meantime though, just to summarise that week again.
Starting with the planets, on 24 March, Mercury is going to be at greatest elongation. It’ll be a chance to really get to grips with the fact that you can see Mercury’s phases, so do look out for that one.
We’re starting to lose Jupiter out of our night sky, but on 20 March you will be able to see its moons perfectly bracketing around the planet itself, so one to look out for there.
And Uranus is also still visible and close to Jupiter in the night sky.
And looking at the Moon, it will be heading from first quarter towards being full on 25 March.
On 20 March the Moon will be close to M44, the Beehive Cluster.
On 21 to 22, you’ll be able to catch the waxing Moon next to the star Regulus.
There’s also a couple of clair obscure effects to look out for. On 18 March, you’ll be able to see the eyes of Clavius. And on 1 March, Cassini’s Moon Maiden as well.
There will also be a prenumbral eclipse visible in the early hours of the morning of 24th and also Comet 12P Pons Brux will be passing by M33, the Triangulum Galaxy, on 23 March.
So lots of things to look forward there and we hope to see you all back here soon, 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 Night Magazine, goodbye.
Chris: Thank you for listening to this episode of the Star Diary podcast from the makers of BBC Sky Night Magazine, which was edited by Lewis Dodge.
For more of our podcasts, visit our website at skyatnightmagazine.com/podcasts, or head to Spotify, iTunes, or your favourite podcast player.