A Lucky Cluster of Middle-Aged Stars - (Caldwell 1 or NGC 188) - Deep Sky Videos

Back to Basics we're going to start a whole new catalog having done all the messier objects I have a new catalog for us to make a whole bunch more deep sky videos of we're not doing NGC are we not no the NGC rather too many objects in the NGC the catalog I want to talk about actually has exactly the same number of objects in it as the Messier catalog probably not by accident 110 actually it's 109 because maybe one of the messier objects isn't really there but uh yeah almost exactly at the same number it is the Coldwell catalog and I thought I'd talk about Coldwell one but I guess so first of all we have to talk about what the cold World catalog is well let's start why it's called the cold World catalog uh it's called that because it was actually created by Patrick Moore um whose full name is Patrick cwell Moore and the reason why it wasn't called the Moore catalog is because M was already taken from Messier and so he decided to use C for corwell for his catalog Patrick Moore is kind of popularizer of astronomy died a number of years ago now presented a very long running program on the BBC called the sky at night now the 30es is a good example of a fairly close-knit Galactic or loose cluster is kind of everyone's idea of what an astronomer is in the UK he was in deep sky videos very briefly he did a one on mesier 40 I believe M40 look for it where is it you won't find it it's not there is he a good person to put together such a catalog was he is he like a legit astronomer absolutely he's the kind of the classic amateur astronomer in that he you know for many years had his own Observatory went out and took pictures of the sky made sketches of the sky so I should say why he's the right person which is that this particular catalog is they're basically things which are nice to look at and so and that's absolutely what amateur astronomers want to do right look at the nice things in the sky it's a beauty pageant it really is and it's sort of the the flip side of the Messier catalog so if you remember back in the the Messier catalog the reason why charl mesier made this catalog was because they were things he didn't want to look at right because he was actually interested in finding comets and all things that looked a bit kind of fuzzy and Comet like that weren't comets he wanted to kind of get out the way so the Messier catalog bizarrely is a catalog of things not to look at the cwell catalog is things which aren't in the mesier catalog but you do want to look at um so they're things which are just nice to look at in the skyp so there's no crossover they're not allowed to be in both catalogues no there are none I believe it's the case none are in both cataloges there it's things which didn't make it into the mesier catalog but nonetheless you ought to be looking at yeah I think we you know we should start with c word one because you know it's a easy place to start so and the other interesting thing about the cobwell catalog is it's arranged in a logical order right the mesier catalog is just random where the different numbers are corwell catalog is actually arranged in order starting with a thing which is furth this North and working its way South so if you live in the Northern Hemisphere you look at the low number Coldwell catalog and if you live in the southern hemisphere you look at the high number Coldwell catalog objects um and so Coldwell one is basically almost at the North Celestial pole it's about four or five degrees off the celestial pole which means that actually from here in the UK is visible all year round it's one of these things called a circum poolar object so it's actually always visible and what is it is an open cluster the thing that we spend so long staring at in the Messier catalog we don't like open clusters they're boring but actually every cluster has a story to tell every object and here we go here's a picture of it so this is my picture taken from my back Garden oh you took this yes one of mine so it's hasn't got a mesier number it's obviously not a mesier object nope it was discovered by uh John herel I think son of William herel sometime in the 19th century and yeah it's just one of these ones it didn't make its way into the mesier catalog it could have done it just Missy happen not to look in that part of the sky I suspect cuz he would have seen it like yeah it's you know as you can see it with a little telescope from my back Garden in the middle of Nottingham so it's not a particularly challenging object it's a bit further away than quite a lot of open clusters it's about 5,000 light years away so relatively distant but it does have some interesting features it is old it's very unusual so if you remember there were these two types of cluster the globular clusters which are the kind of impressive round spherical ones very you generally with very many stars and then there are the open clusters which tend to be kind of more ragged in appearance fewer number of stars not so well bound together globular clusters are all very old and have been around you know almost as long as the universe has been around the open clusters tend to be much younger they tend not to last very long because they're not terribly tightly bound together they're the smaller collection of stars so over time Stars just escape and they just get sort of torn to pieces and so the Stars spread out around the Galaxy what's interesting about cold world one is it's old as well as being an open cluster so it's one of these ones that kind of didn't form at the very beginning of the formation of the Milky Way but it is about 8 billion years old and so that's quite old for an open cluster it's unusual for one to be that old because normally by eight what by 8 billion years you would have just completely dispersed exactly they just have spread out and in fact you know most of the Stars we see around us the armed in clusters would have been born in one of these open clusters and over time they

just kind of get smeared around the Galaxy overall possibly the sun almost certainly I think probably almost all stars formed in a cluster of some size you know it might have been quite a small cluster but they all formed in these clusters Stars don't form individually they form in groups what's held this one together why has it stood the test of time so I think there were a couple of reasons firstly uh it's quite massive so actually you know it it was quite well held together by its own gravity secondly it Formed quite a long way out in the Milky Way that means that it didn't keep running into other things as it was kind of orbiting around the Milky Way you know if you're form relatively close to the center of the Milky Way you're going to keep there are spiral alarms and there are other clusters and everything's a bit crowded and therefore you're more likely to kind of end up gravitationally interacting with the kind of things which rip clusters apart this one formed relatively long way out which meant it probably didn't encounter too much stuff and it's also on an orbit which takes it quite a long way out of the plane of the Milky Way and again that means it spends a lot of its time away from most of the action in the plane of the Milky Way it has to plunge through from time to time as it kind of orbits around but most of the time it's away from where most of the things are that could rip it to bits so it's just had a whole series of things in its favor in terms of it surviving that long and which is why it's still here 8 billion years later I would imagine this would make it quite a desirable Target for astronomers something that's stayed intact for so long it's sort of interesting I mean it's an interesting laboratory for studying for example the studying Stellar structure and star formation well not star formation CU it's quite old now but you know how stars have evolved because it's that you know it's that middling age you know you've got your very old globular clusters which are what 10 12 billion years old you've got your very young open clusters this is kind of middle-aged uh collection of stars all more or less the same age but all middle-aged and so it's sort of an interesting laboratory for studying from that point of view the only thing that kind of counts against it a bit is it's quite a long way away and so therefore it's that much harder to study in detail cuz it's quite a distance away it's also known as NGC 188 it does have an NGC number as well so you can count this as another of the NGC objects if you want as well but I've just happened across a paper that came up on this Archive of pre-prints of papers somebody has used the we talked about it before this Gia satellite which is um studying Stars the positions of stars with exquisite accuracy and one of the things that Gaia measures is it measures this thing called proper motion which is the motion of the stars on the sky because it's measuring their position so accurately it can come back a year later and see how far they've moved and so one of the nice ways of identifying stars in a an open cluster like this is that all the stars because if you go back to the picture for just a second here you know you can see there's a cluster in the middle but there's a whole load of other stars as well it's not just the Stars you know and that presumably there are even when you get quite close to the middle here there are stars around there that had nothing at all to do with the cluster they're in front of it they're behind it they're not associated with it but the nice thing is that all the stars that actually are in the cluster will all be moving together and so one of the ways you can identify which uh stars are actually members of the cluster is by studying these proper motions studying the Motions of the stars and all the ones that are moving together are almost certainly members of the cluster and ones that are just moving in random directions probably aren't so they use data from guia to kind of really clean up that these are the stars which are actually in that open cluster and use that to study it in a much more kind of robust way of actually making sure that they really were just studying the stars that were members of that same group Professor surely these stars have their own motion within the cluster itself too though as they interact with each other but is that insignificant compared to their overall motion of the cluster as a whole it's smaller it's not insignificant and in fact there's information in that too right because you also you can study the Motions of the Stars within the cluster um and that tells you stuff about for example what the mass of the cluster is so you can use the Motions to figure out what the mass of the cluster is but it's like you know it's like you've got a swarm of bees that are kind of all buzzing around doing their own thing Within in the Swarm but the whole swarm is moving off in a particular direction and so you can you know and the dominant effect is that overall motion so you can use that to identify the cluster when it comes to stars in the Milky Way and the Stars you're talking about here as in the stars at that a part of the cluster and the stars that are in the foreground or background is that the only way we can differentiate can we use red shift or can we use the chemical composition of the Stars so well the I mean the red shift is basically measuring this speed so I talked about the motion that way but of course there's also motion that way or that way and again you can use that to say actually all these stars are going to have be moving with a common red shift or blue shift and so you can use that as a further piece of information and of course the other beautiful thing that guia measures it actually measures the distances of the stars as well it measures this thing called Parallax which again go back and do a little bit of physics here the as the earth goes around the Sun you end up looking at the stars from slightly different directions depending on where on its orbit you the Earth is and that makes the stars appear to wobble

backwards and forwards as you view them from slightly different perspectives and so you can actually use that effect to measure the distance to the Stars so we actually know the distances to these Stars which gives you another way of saying these are the ones that are probably in the cluster because they're the right distance away the ones in the foreground probably aren't background probably aren't so there's lots of kind of bits of information that all go together to figure out which things are members of the cluster and which aren't you probably I mean in principle you could use things like the chemical composition as well but that's probably something you want to measure in that you actually want to say okay do all the stars in this cluster have the same chemical composition or did some of them format a more recycled material and therefore have more heavy elements in them so rather than using that as something to actually identify cluster members it's something that having identified the cluster members you probably then want to measure you told me at the start the cordwell catalog was you know well I used the term beauty pageant you told me they would be more spectacular I was expecting of like some big pink nebula and a horse's head and all sorts of stuff that that's I wouldn't call that a complete and utter Beauty it's not and there were good ones to come so we should make some more but because of the way they're ordered they didn't start with the prettiest one they just start with the one which is furthest North thanks for watching look I don't know if we're going to do the whole cold well catalog maybe we will we'll have to have a talk about it of course we've already done all 110 messier objects I hope you've seen that playlist I'll link to it on screen and in the description and if you'd like to see more objects cover here on deep sky videos well one thing you could do is support us on patreon just like these people whose names you see on the screen of course the best thing you can do is watch and share the videos but a little bit of extra support on patreon goes a long way