M50 - Spinning Stars - Deep Sky Videos

so in preparation for this deep-sky video i essentially through a virtual dart at the list of objects that hadn't been done that we're on the website and i landed on em 50 i just closed my eyes and pointed of course i went to Wikipedia to look it up and there were two lines on Wikipedia about em fifty and the most interesting thing about it seemed to be that it was heart-shaped so I figured this was going to be a tough one so it happens to be an open cluster which is probably one of the less spectacular kinds of objects in the messiyah catalog its young about 130 million years old and it's just a collection of stars that would have formed out of the same molecular cloud in the same location in space and are pretty much the same age as well okay so I need to find something interesting to say about this open cluster so what I found was a paper which was part of a monitoring program which looks at the variability of stars in clusters like this now stars can vary for a number of reasons they can vary for intrinsic reasons because they're big pulsating stars that vary on a regular basis or they're cataclysmic variables that throw off material occasionally or they can vary through extrinsic reasons for external reasons either because something is passing in front of it I'm causing it to dim and that's a really exciting way in which we're uncovering lots of extrasolar planets at the moment or simply because they're rotating and they have some sort of rotational variability because of well not sunspots but of star spots variations on the surface that will appear and reappear and cause little 1% dips this paper was monitoring it for those those last two reasons but to do this of course you have to take lots of images over a very long period of time for the observing run in question you know three four six nights and then separated by a gap of another of ten months where they went back to the telescope and for each one of these nights where they were sitting at the telescope they were basically taking a seventy-five second exposure of this object reading it out taking another one looking at moving to another object doing the same thing moving back moving back and doing it over and over again so you can imagine how tedious this observing run must have been but in the end they had a really good a lot of data for m50 and we were able to determine the rotation periods for a lot of the members hundreds of the members of stars in this cluster so doing a big census of this cluster and really getting to know the stars and they're a bit better is that yeah absolutely because there are a few fundamental properties that you want to measure about stars you want to measure their brightness their color their mass and the rotational period and so for an open cluster like this it's interesting because you know the distance to it so you know all the stars are roughly the same distance away from you and you also know that because they formed at the same time they're all roughly the same age so then you can start to look at variations of the rotation properties with some of the other properties of the Stars like their mass like their metallicity so this is not the actual paper in question but it uses the data from it so what we're looking at here is a compilation of very similar studies and so m50 is this panel here so that's our object right here but what we're looking at is a series of other clusters for which these observations have been a rip made and they're arranged in increasing H so you can see up here we've got 1 2 3 million years these are these are stars that are just barely being formed and then they increase in age we get up to M 50 at 130 million years still a young cluster and then we go down to something like the Hyades open cluster which is quite old you know 600 million years so the plot that we're looking at in each one of these panels so each one of these dots is a star in that cluster and the mass of the star is increasing this way and so you're getting up to note one here which is the mass of our Sun and then on the y-axis here you've got the period so how long it takes to rotate about its own axis and so for our Sun that is about 24 days the exact number is is a little complicated but it's about 24 days the more to the right the star is the more massive it is and the higher it is on this plot the more slowly it's spinning the longer its period so m50 here is one piece of this jigsaw puzzle that's evolving in time and you can see how things are changing here so first of all when with a cluster like this which is really young you've got your stars forming but they've got a real scatter they've got a real range of periods about two orders of magnitudes or about a hundred times and so as you move up here you see an interesting pattern form and it really sort of comes into its own at about this age with them 50 which is as you go up in mass you see sort of a tight sequence form here and that means the lower mass stars are rotating faster but the higher mass ones are rotating more slowly and there's a lot of physics behind this which is not entirely understood which is why the data from M 50 is one important part of this puzzle to try to understand the physics of what's going on here but essentially it all comes down to angular momentum because a few things can happen as the stars forming it's contracting and so it's actually spinning up so just as a figure skater as they pull their arms in as they bring their mass closer to the center they will spin faster so a collapsing star will spin up as it gravitationally collapses this is complicated because it's usually surrounded by a disk of material that's that's helping it form and so there's coupling between the star and the disk which just gets a bit complicated but then once it's sitting on its own these stars are just just normal low mass stars sort of living the main part of their life there on what we call the main sequence and so they're sitting there they're rotating but as they rotate they're throwing off material through their stellar wind so this is a coupling of the magnetic field with the plasma in the star and the material is released off and blown out and we see this from our own Sun and you know solar storms will send charged material our way that will impact on you know my television reception or whatever the result of this in terms of the rotation period of the star is the opposite of the gravitational contraction as the material gets thrown off the angular momentum is conserved and the star starts to spin down its period gets longer and it rises up on this curve okay and for complicated reasons of physics we think that that this then converges as the Stars get older as we see in these increasingly older snapshots of clusters we don't have the fast rotators anymore and we have a really tight sequence relating the mass to the rotational period and all those stars have been have been spun spun down and they're all rotating at a longer period I can't provide you with any answers here m50 in this clique case is essentially a snapshot of a cluster marking one age sequence in in this stellar evolution so we can't sit and watch the stars evolve over hundreds of millions of years all we can do is find different clusters that are of different ages and see how things change with age this is really opening up a fairly new field called gyro chronicity which is essentially using the rotation period of a star to estimate its age and not just from a cluster where you essentially know that they're all the same age and you can figure out what that ages but any old random star and so that's quite a quite a new field but but this is all sort of material that's feeding into our understanding of how stars evolve our story was not already good enough at getting the age of stars without having to use this extra elaborate feature of them to guess the age now started star you're pretty complicated and there's a lot of subtleties and and as I said very interesting physics that goes on that means you know remember there's only so many measurements that we're able to make of a star as we sit here on earth so yeah there's still lots for us to figure out so this is what I wanted to show you it's the grave of Charles Messier his final resting place there's actually surprisingly few markings on the grave now when we first came in there was a list of all the famous people buried in this cemetery it's one of the most famous cemeteries in the world and Messier wasn't actually on there I think this would have been very difficult to find if it wasn't for some helpful information on the Internet

Channel: DeepSkyVideos

Views: 59,283

Rating: 4.9724998 out of 5

Keywords: astronomy, m50, messier 50, stars

Id: 17LITLns-pk

Length: 8min 47sec (527 seconds)

Published: Thu Jul 14 2016