What's in the night sky in the week of 17 to 23 July, 2023 in our weekly stargazing guide. Venus's changing phases and Pluto at opposition are the highlights of this week's stargazing guide.
Chris BramleyHello 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 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 17 to 23 July. I'm Features Editor Ezzy Pearson and I'm joined this week by reviews editor Paul Money. Hello, Paul.
Paul Hello Ezzy. Nice to see you again.
Ezzy Nice to see you. And what can we expect to see in this week's night sky?
Paul We start off on the 17th itself. Now it is in the morning sky, we're looking at 03:00 AM.. We mentioned towards the end of last week that Taurus is back in the sky, especially the Hyades and Aldebaran. Well, there's something else to look at near them and that is on the 17th and 18th, the minor world vesta. This is the fourth one that was discovered, which is why it's called 4 Vesta and it will be nearby to Aldebaran. It's about a degree away from Aldebaran. You'll need binoculars. Vesta is at least +8.0 magnitude, whereas Aldebaran is easily naked eye, very bright. You won't be able to mistake that, so it's worth having a look at. You do need star charts because obviously there are other stars in this vicinity as well. But the reason why we say 17th and 18th, you look for the one star that's moved. To hopefully you get two mornings clear and you can compare the position. So draw the star positions, and then the next morning draw them again and then compare them and see which one has actually changed position and that will be Vesta.
Ezzy And that's, in fact, exactly how they found most asteroids in the first place. Definitely when I was doing my degree, we had to take images and do what's called blinking. So those two images that were taken several hours, days apart and tried to see what part... what object it was that had moved across the night sky. So if you do fancy some astrophotography, maybe you can try that and see if you can see Vesta moving across the night sky as well.
Paul And of course, they did use that technique to find Pluto, and we'll come to that towards the end. So, yes, that is a morning thing. And again, they won't be very far above the horizon, so that will have an effect as well. So bear that in mind. Now, 19 July, we're back into the evening sky. We had a challenge at the end of last week whereby you were trying to see Mercury. Have another go on 19th. And the reason why I'm suggesting this is that the Moon has passed through new phase and will be an incredibly thin, slender crescent to the upper left of Mercury. So again, if you can't see the Moon, Venus is still in the sky. So we've got four planetary bodies hanging in the sky. They're very low down, 10:00 PM in bright twilight. We'll have Mars, which will be difficult. We'll have Venus, which is the one you should be able to spot first. That should lead you to the crescent Moon. You got to remember the crescent Moon. It's very thin. When it's thin, it isn't actually that bright when it's an extremely slender crescent. And then to the lower right of the Moon, you've actually got Mercury just above the horizon. So it really is a challenge because they will set very, very quickly. This is now the problem with Venus and Mars. They've been dropping quite rapidly towards the horizon as such, so they will be carrying around with Mercury, they too will drop to the horizon. So this is not a very good apparition for it, but always think it's a nice combination. You've got four planetary bodies there to see if you can see, so use binoculars. But as we always say, absolutely make sure the sun has set first. That is golden rule for safety. Make sure the sun has actually set.
Ezzy At least in the evening sky. Once the Sun has gone down, you can be pretty sure it's not going to come back up again or lose track of time and it'll suddenly pop up like it would in the morning sky. So just make sure it has fully set, completely set. And then once that happens, get out there and try and find those four.
Paul Now, all this week, you can do something different with Venus. You have to remember that Venus is bright and Venus with care, can be spotted in the daylight sky. It's a challenge that Pete Lawrence has often mentioned in the magazine and we cover it in the July issue as well. Because Venus is doing something interesting. Throughout the month of July, the phase is diminishing, it's getting thinner and thinner. So Venus is looking more and more like the Moon without the craters. But if we look on 19th, around about 05:00am, so the sun will be getting low. But if you work out well... I mean, if you especially if you got a Go-To telescope, it's quite easy for got a Go-To. I know it's lazy, but if you got a Go-To telescope, ideally do an alignment beforehand and then hibernate it. And when you bring it out of hibernation, just tell it, go to Venus and it'll take you to Venus. Not literally, it won't fly off the Earth's surface, but you know what I mean. So it's an easy way of doing it.
Ezzy I don't see it as being lazy, I see it more as you are taking away some of the grunt work. If you're not trying to learn your way around the night sky, if you're literally just trying to do a project or something like that. You're just making your life a little bit easier. I don't think there's any shame in using Go-To to help yourself.
Paul Well, let me tell you a brief little story. Just the other week I decided there's a mount that's been set up outside all the time and I haven't really been using it's. It's been covered over because I've been using some of the other more portable mounts. So I went back to it and when I looked at the date that I'd changed the settings, it was July last year. I went and used that to find Venus in daytime, and it wasn't in the eyepiece. So I thought, oh, this is serious. But it was in the finder. Just. But there's a little moral to this story now, make sure you haven't knocked the finderscope, because I spent ages trying to find Venus, manoeuvring it into the centre of the finderscope, and it was nowhere near. Eventually I had to realign at night the next night, then go back, and then I could find it and I had to realign the finderscope. But when I found Venus in the finderscope, it was easy as anything. And I used binoculars in the middle of the day to find... 10x50 binoculars and I found Venus as easy as anything. So I mean, as we get towards the end of the month, the disc is getting bigger, so you will actually start to notice the crescent, even in 10x50 binoculars. But obviously a telescope will make it more obvious. So there you are. Start watching the crescent of Venus as it starts to shrink over the next few weeks. But bear in mind, it will gradually start to get closer and closer to the Sun as well. So again, we always have that caveat with the safety. You must be safe because otherwise you could damage your eyesight permanently. Now, just as twilight begins on July 20th – this is late evening, so it's literally border time, daytime and twilight. We'll have the crescent moon. This is the 20th, remember. the slim crescent moon will be a bit more obvious, and it is virtually directly above Venus. So even if you can't find Venus, you should be able to find the Moon and then look directly below it and it'll be about just under seven degrees. The moon north of Venus itself. Or above Venus, I should say. So you've got the crescent Moon, and then if you put a telescope on Venus, you'll have a crescent Venus as well, so you'll be able to compare the crescents. I love doing that because it reminds you sort of thing that Venus goes through phases just like the Moon does, sort of thing. It's the only planet that... Well, Mercury. But Mercury is a lot harder because, of course, it's always nearer to the glare of the sun, isn't it? But Venus, you get a chance to see the crescent quite easily. So do have a go at that. Finally. Well, we like challenges, and this is a big scope challenge. Now, anywhere from an eight inch upwards. I know some people have seen it with a six inch, but that's on the perfectly dark skies and in a less crowded area of the sky. I'm talking about Pluto, because Pluto comes to opposition on 22 July. Yes, it's magnitude 14.4. So this is why you need a big scope. So it's worth having a look at. If you've never seen Pluto and you've got a big scope, do have a look for it. This is the time when Pluto now becomes visible throughout the actual night. And a bit like we mentioned, you remember we mentioned about Vesta and doing the blink comparator. We mentioned that Clyde Tombaugh actually discovered Pluto using a blink comparator comparing photographs or thing. You can do the same thing. And that would be perfect to do this for Pluto again now, because it is moving very slowly against the background stars and so now visible. You need it's low down in Sagittarius, so it's suffering a little bit from that. So there will be some reduction in the brightness because of the position in the sky. But if you look around about the southern point, when it's highest in the south, around about midnight by then, then you should be able to pick it up with a large scope. And if you do I mean, admittedly it used to be the ninth planet, but now, of course, it's the first of the dwarf planets, so have a look at it. You never know if you've got a big scope well worth having a look at it, as long as you've got a clear southern horizon to pick it out. It's nearly at the border, by the way, of Capricornus, so it's only just in Sagittarius at the moment. But it is a challenge. So if anybody sees it or photographs it, perhaps contact the magazine.
Ezzy Yeah, exactly. There is a reason why Pluto wasn't discovered until the 1930s. It's not the brightest thing in the world, as you said, +14.4 in magnitude, but it's definitely one to check off because most people have seen all of the other planets. Most astronomers have seen all of the other planets, but Pluto is the one that's a bit of more of a challenge. So, yes, if you manage to see that one or snap an astrophoto, we always like to hear about it. You can find details about how to contact and send those over on our website, www.skyatnightmagazine.com.
And thank you very much for taking us through all of the week's highlights Paul. To summarise, on 17th and 18 July, the minor planet Vesta will be just above Aldebaran in Taurus. You will need star charts to find that one. On the 19th, you can see Mars, Venus, Mercury and the Moon altogether in the night sky. They will be very low and won't be visible for very long, so look for those at around 10:00 PM. Throughout the month, you'll also be able to see Venus's changing phases. They will even be visible in the daylight sky. But on 20th you can compare Venus's crescent with that of the Moon, as it will be directly below the Moon on 20th.Then on the 22nd, Pluto will reach opposition in the constellation of Sagittarius. That one is a bit of a challenge. It's only +14.4 magnitude, so you will need a big telescope to be able to see it. But that is the week's highlights. If you want to make sure to catch next week's highlights, do subscribe to the Star Diary podcast and we will see you then.
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.
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.
