 Greetings and welcome to the Introduction to Astronomy. In this video we are going to talk about using the Eclipse binary stars lab. So we're going to be looking at stars that pass in front of each other and will dim their light from each other. So as one star passes in front of the other it blocks out some of the light from the other star. And there will be a lab worksheet for you to look at and as always you may want to make sure you look at the main content material that are not the simulators that gives you some additional information for these and then the simulator itself is what I am going to go through here and discuss just a little bit about the controls. So let's go ahead and get started here and when we open the simulator what we'll find is something like this with a number of different screens available and you will see the actual here the image of the system itself. This is the light curve that you'll look at showing the what they call the normalized flux. So what you would normally see would be one that's the normal amount and then when the eclipse occurs when one star passes in front of another there will be a dip in the amount of light and when the other star passes in front you'll see another dip so when the bright star is being eclipsed then you're going to have a larger dip more of the light is going to disappear. When the fainter star is being eclipsed you're going to have lesser material lesser amount being blocked out. There are some various presets that you can use here preset systems and you can also adjust the properties of each of the two stars and the system themselves and you can actually watch the animation if you want to watch. So if we wanted to look at for example to run this animation forward we can click on start animation and you can watch the red line shows where you are at that point. So you can see that as one star passes in front of the other there will be a dipping in the amount of light that is visible from the entire system. Now let's look at a couple of examples here and we can look at for example some of the presets there are a whole bunch of presets here for you to look at so there are some examples that you'll be asked to look at and there are specific data sets for for sample stars that exist. So we can look at one here let's look at TWCAS and this is an example of the curve that we see the solid line is the theoretical curve based on the numbers that you give and the other curves are the data points are the observations so you'd want to be able to match them to make them look as close as you can. Now in this case as you run the animation forward you will see that one star does not completely block out the other and when something like that happens then you will get a curve that is rounded at the bottom or more pointed and that is because you're not blocking out fully blocking out the star so more and more of the star gets blocked out you reach a maximum point and then it comes back so it'll give you almost a v-shape here in the light curve now there are our examples where it is completely blocked out and we can look at another example like that to see what happens when the light is completely blocked out and let's look at this one DMDEL and this is one where we can see the stars and see that as we look at the system and run the simulator forward we can see that one star completely blocks out the other or completely passes in front of the other and in those cases you will get you will get that the two that it actually will bottom out and it will be flat there will be no change for a while and that's because no more or less of the star is being covered at those times so that's one of the examples and one of the other things you'll have to look at is to be able to try to match them so you can see here as this is set the data points really don't match very well with the observations you can see that there's a big difference in certain areas right here there's a big gap between the data points and even here they just don't fit very well so we can adjust the parameters and that's what you're going to do in some of these you can look at adjusting these parameters you can change things like the mass well that doesn't change a whole lot with the light curve so that won't help you a whole lot but the radius you can adjust that to try to get things matching up you can adjust temperatures which will also adjust the curves and you can see how that can bring things a little bit more in line and you can you can adjust the properties of star two as well so you may have to play around with these a little bit to try to get the curve to match as best you can so you can change various properties change the sizes the separations of the objects to try to get the best possible curve that you can to fit these and i'm not going to spend the time here to get a perfect try to get a perfect match but you can play around with some of these and try to get a much better match as you can see we're already a lot better than we were before so we already have a significantly better fit to this there are still some things you could play around with but then you'll want to play around and get the match that fits the best on these and hopefully that'll give you an idea of the various orbital parameters that you can change so those are most of the things that you will want to play around with during this and of course there will be other places in the instructions where it will ask you to do very specific things so that concludes this explanation of how to use the eclipsing binary simulator we'll be back again next time to look at another one of these labs so until then have a great day everyone and i will see you in class