Star Diary: 18 to 24 July

Neptune, the Pleiades and asteroid that used to be a comet are all visible in this week's night sky.

BBC Sky at Night Magazine Star Diary podcast.
Published: July 17, 2022 at 8:00 am
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What's coming up in the northern hemisphere's night sky in the week of 11th to 17th July.

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Transcript

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 skyatnightmagazine.com or digital edition by visiting iTunes or Google Play.

Ezzy Greetings, listeners. Welcome to Story. A weekly guide to the best things to see in the Northern Hemisphere's night Sky. In this episode, we'll be covering the coming week from 18th to 24th July. I'm Ezzy Pearson, the magazine's news editor, and I'm joined on the podcast today by reviews editor Paul Money. Hello, Paul.

Paul Hello. There is another exciting week and it is a good week this week.

Ezzy Oh, absolutely brilliant to hear about that. So what are your recommendations for this coming week?

Paul Well, the good news is there's lots happening. The bad news is in the mornings sky. So we have to get up again.

Ezzy A couple of more early nights.. morning sky.

Paul We're astronomers! Heaven sakes, we should be getting up observing these things, you know, you shouldn't be a fair weather astronomer. Just stay in the evening sky. There's lots happening there in the morning sky as well. So last week we ended the week on the 17th with the moon next to Vesta and occulting tau Aquarius. Well, the next morning, July 18th. So all the action happens now in the morning sky because the moon's back here and the next morning the moon is actually directly below Neptune. So Neptune obviously needs a telescope, large binoculars to actually spot. But at least you've got the moon to actually guide you to it sort of thing. So there we are. Now, Jupiter is to the left of Neptune. And so the motion of the moon means that on the 19th the moon is directly below Jupiter. Now they will be a naked eye, obvious naked eye you got... So you'll see a star... How many times do we at the magazine get comments about "what was that star next to the moon the other night?" Something I get them when I do my radio spot, sometimes for a local radio or something. What was that star next to the moon? That was no star. That was a planet. Which of course means wandering star. But anyway, so they said, we've got.

Ezzy The reason they have that name. Planetes Asta, meaning wandering planet. Sorry, wandering star.

Paul Wandering Star. Yes. Yeah. That would be Planet planet, wouldn't it. Wandering planet. But on the 20th the moon moves constantly, doesn't stop of course on the 20th, the last quarter Moon lies in Pisces. Then on the 21st, it lies to the right of Mars. So again, we've got this parade of planets still taking place. On the 22nd is to the left of Mars. So sometimes they are directly underneath or close to the actual planet. Sometimes the moon is either side of the planet, it's just down to the positioning. You know, perhaps next month it'll end up being either side of Jupiter and then directly below Mars. It's just the quirk of the way how the moon's orbit goes and the motions of the planets as well. This is why it's all fascinating. You get different combinations and no one event is exactly the same as the other. The role unique in their own right. But on the 22nd, when it is to the left of Mars, the Moon is also close to Uranus. So again, a guide to find Uranus. Uranus will be slightly to the upper left actually of the Moon. Then finally on the 23rd here, it's actually below Messier 45, the Pleiades the star cluster by several degrees, admittedly, but by now the Pleiades will be becoming easier to observe. It's higher in the sky. So I always get excited when I see the Pleiades and the Hyades with Aldebaran back into the evening sky. I'm one of those that can't wait for the summer solstice to be over because I know, I know the night to draw in. I can't wait for the summer's to be over in the night start drawing. And I do like the summers. But I'm an astronomer. I do like the dark skies. So there we are. So if the moon is below messier 45 on the 23rd, then the next evening it'll be above Aldebaran. And I say it's nice to see Taurus coming back into view. Now, The parade of planets. We've still got Venus. Venus will be further over, but it's next week when the moon reaches it as such. So Venus is still visible, but it is still trying to drift back into the solar glare. So we're lucky we can actually see it. We see simply because it is so bright and that's what keeps it visible. However, we have lost mercury now completely, so we've lost that line-up of the naked eye planets in actual order. But that's just the way it goes. So I hope we got it last week when we could actually see them. I want to finish with something rather unusual. And, you know, it's nice when you do these simulations of the night sky and suddenly something pops out and you think, wow. But that that's that is an unusual event because it's something different. And what we want to do is I suggest you take a peek at an asteroid that'ss also been designated as a comet. It's a dual identity here. A dual identity. It was originally discovered as Comet 17P/Wilson-Harrington. That was back in June 1949, when it was discovered. But then the comet was lost. So it's like everything else. I mean, sometimes these things happen. Yes. We do lose some of these objects in the night sky, but it's often down to perhaps they they've gone fainter than they expected. They kind of especially comets can disintegrate.

Ezzy Oh, yeah. Comets. Comets break down all the time.

Paul There are running nightmare aren't they, for predicting. I remember Comet Ison. We were all excited by that and it disintegrated sort of thing in a comet atlas did the same thing as well. But in this case what happens is often sort of thing, perhaps the oribt, there wasn't enough to make the orbit as accurate as people wanted. So when they search for it next time, it probably wasn't quite in the place it should be. But then an asteroid was discovered in 1979 and that was given the designation 4015/WilsonHarrington And the reason why was given the designation 4015/Wilson-Harrington was because in actual fact they started to realise that it was actually the same object as the comet because they were in a identical orbital pass and exactly in the right position for both the comet being predicted and the asteroid itself. So they finally decided in 1992 that it definitely was the same object. And so far, as far as I'm aware, it's about one of the few objects is designated by two ways. Comet and an asteroid. Found first as a comet now seen as an asteroid because it doesn't have any activity. So when they found it was a comet, there was a clear cut tail. That's why they designated as a comet. It's over a thousand years orbital period, by the way. So that sort of also tends to imply it could be a commentary body, but it's now obviously outgassing all the ice and there's only the hulk left. Yeah. So I think that's amazing. So the thing yeah, the thing about this is that it actually though is moving past a reasonably bright Star, a Naked Eye Star, again, eta Piceum. And again, we love these events because it draws your attention to them. So you'll be able to see this unusual object, which is around about magnitude 7.4, 7.5. So, you know, well worth having a look at and from the 19th to 20th. It passes above Eta Piceium. On the 19th. It's pretty close to Eta Piceum. on the 20th, ironically if you're a deep sky imager, you might want to try for this. I know it's like night, but it's actually above Messier 74, the galaxy. Now, it's not an easy galaxy anyway because it is face on. It's quite dim. But you know, again, we like challenges as such. So there we are. So pick out an unusual object which happens to be a reasonable brightness at the moment. 7.4 So you know, that's quite good. That should be visible in binoculars. You'll need a good star chart and I'm sure the magazine will have one anyway. And there we are. We can pick out an object that was originally discovered as a comet but is now considered an asteroid as well.

Ezzy I always love things like this where it kind of shows are evolving, understanding of both like what objects are in themselves and also of what is a comets, what is an asteroid. You know, those are both questions that only got really answered relatively recently when you sort of look to how long we've known about, you know, there's these things, bright points of light floating about in space and comets that come and visit every so often. But actually like a studying of comets and asteroids is relatively recent. And so sort of seeing that kind of evolving understanding, I think is always fascinating. When you get these objects. It sort of it wasn't necessarily that we were wrong. It's just that's part of science sometimes. But sometimes you do get stuff wrong and sometimes you have to admit that and move on as you learn new things.

Paul And the reality was when I first started, you know, it was because of it's the coma, the actual material coming off it. It was clearly designated and we would have classed it as a comet. And in those days, nobody ever thought that one could be the other, you know, that could interchange. And as as we now realise comets are outgassing, so at some point they're going to run out so their ices and when they run out of their ices there's only going to be the rocky hulk left and therefore if they discovered now they would look like an asteroid. And that's exactly what happened with Wilson-Harrington, you know, so it was amazing. As you say, our understanding has come on in leaps and bounds. So this is a good time to see an object that started off as a comet but now looks more asteroidal instead sort of thing. We got one final object, its a challenge, but we have to mention it. On the 20th Pluto is at opposition around about 14th magnitude. It won't be too far away from Messier 75, a globular cluster in Sagittarius. But you will need a large telescope. The. Is quite low down in the sky. But when the objects reach opposition it does mean they are visible from then on all night long, although the summertime the whole night long isn't exactly very long, is it? But you know, if you got large scopes from now on is the best time to actually start trying to hunt down and check out Pluto. But there we.

Ezzy 14th magnitude is hard, but but possible again always a challenge, especially if you're looking to if you've been doing this a while and you're looking for something a bit new to to challenge you and get out there, see if you can see Pluto as it moves across the night sky. But thank you very much, Paul, for taking the time today to tell us everything that's happening in the night sky this week.

Paul It's been an absolute pleasure. Thank you.

Ezzy 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 Up 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 the detailed star charts to help you track your way across the night sky. From all of us here at BBC Sky magazine. Goodbye.

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Chris Bramley Thank you for listening to this episode of the Star Diary podcast from the makers of BBC Scotland Magazine. For more of our podcasts, visit our website at skyatnightmagazine.com Or head to aCast, iTunes or Spotify.

Authors

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.

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