so to button up the topic of spectra classification and stellar surface temperature now when I look at this image that we were looking at again in the last video and just to point out some real key parts of it which is that you know the hottest stars Oh stars on the top of this image bees are cooler still b5 cooler still all the way down to the coolest that are displayed em twos and just look at the very distinctive differences in the spectrum for oh stars it's very simplified isn't too many lines up there a zero stars are going to have the strongest at the Balmer lines and get the thickest lines that you see right here for each gamma is what that reads each beta is over here in the you know look steel to us in reality but it's almost a light purple here and then the H alpha or the red line over here on the far right it's the boldest and strongest line for the a zeros the coolest stars that are displayed in this image m2 s at the very bottom just look at the plethora of lines they have down there and of course things that we find on the spectrum of a cooler star like titanium oxide t IO and a neutral sodium na one at the neutral iron Fe one that you just don't see in hotter stars so the significance is that you know prior to this we thought we had to analyze the flux of a star over all the different wavelengths that it emits so we could find the peak of its plunk curve and therefore use fiends law to determine its surface temperature but this is telling us that a snapshot of the spectrum in the visible part allows us to do the same thing a computer of course we handle this very well and look at those snapshots of spectrum realize oh it's of this very specific spectral type and therefore since spectra type is correlated perfectly the temperature at the surface we know the star's surface temperature as well so it's a much easier task through the understanding of modern spectra to deduce Stiller's surface temperatures as opposed to the old method of you know using eyeballs first of all and analyzing a whole lot of different wavelengths with a much more time intensive observation period so that's the importance the significance of this image here your author in your textbook has this image that you'll see on the next slide here and it too is taking the major spectral classifications will be a FG km on the Left OB a fine girl kiss me and showing us the approximate surface temperature for the different spectral types you know 30,000 kelvins is kind of a nice ballpark figure for the later types of O's you know oh seven oh eight oh nine and twenty thousand kelvins for a B star in ten thousand kelvins for a nice at zero star and M stars the coolest of them all you know surface temperatures of only about three thousand kelvins which makes them glow a nice dull red in the visible range the middle category of the table you know show you the note worth the absorption lines what a computer or what anybody else will be looking for to deduce if you have this spectral type hey perhaps you know some star names perhaps you've had a stir 110 with me and you know some of these more these the brighter stars in our sky and the Mintaka is the belt star in Orion look at a ride in the evening sky in the wintertime I mean tacos the right hand star of the belt and it barely made the Oh class it is an oh nine star but nevertheless it is very very hot at the surface about 30,000 kelvins auslan Orion rides with a kneecap star looking very bluish white to us and it's a b8 Vega you know the original star to come up with stellar magnitudes and a zero star Sirius the brightest star in our sky besides our Sun about an 81 so very close to being about 10,000 Kelvin sat their surfaces versus our Sun which is a g2 star Alpha Centauri is the closest star to us you know the system and both of us have about the same surface temperatures g2 which means what else yeah we both appear to be about the same color right since the spectral traffic color go hand-in-hand today when you get to the K star Z's their orange e stars Arcturus and Aldebaran Arcturus at the brightest star in the summertime's guy up in boots you know Deborah Ron is the eyeball of the bowl in the winter time sky the M stars Betelgeuse is probably the most famous one in the shoulder star Orion and then of course Barnard star the star with the greatest a proper motion that we know of is also a red star okay in the next segment we'll figure out how temperature is related to basically mass of a star because the star is crushing itself to generate the temperatures in the core necessary to you come up with the nuclear fusion temperatures ignition temperatures and ultimately determine the surface temperature of the star as well after it's done actually doing that yeah thanks