so here we go two final things to talk about there is a way that we can classify stars based on what their spectrum is okay there's a way that we can classify stars based on what their spectrum is and there's billions and billions and billions and billions and billions and billions of stars out there and so would we expect there to be how many types of spectrum would we expect there to be like how many different patterns would we expect there to be in the universe so it seems like there would be a lot because there's billions of stars but the people who are actually studying this a little over a hundred years ago realize that even though there's billions and billions of stars almost all of them have just a few different spectrums turns out stars even though there's lots of them are all very similar to each other okay and because they're so similar to each other we can classify stars based on which shape their spectrum looks like out of just a few categories so let me get a blank sheet of paper to write on I'm running out of paper give me a blank sheet of paper here we go so this classification of spectrums is called the spectral type spectral type okay spectral type and I've seen some textbooks called this the Henry Draper classification but I am not gonna call it that because these spectral types I don't think they should be named after this guy named Henry Draper don't even worry about who he is let me show you the picture of the people who actually did the work and who came up with the classifications for stars based on spectrums here we go check these people out right here these are the people who did the work to come up with the spectral types the classification of stars based on their spectrums okay and here's my question can you figure out by looking at this picture why this work these spectral types this classification was not named after these people can you figure out why it's not named after these people keep in mind that it was named over a hundred years ago that's right it's because it was it was the 1910s and you probably noticed these are women and women did not get a lot of credit for their work in science these women were actually criticized at the time for not becoming housewives for going into science instead of being a good wife it was it was a crappy time the past kind of sucks in a lot of ways it's pretty bad in fact the woman who was probably this should be named or after is this woman right here she was the one that came up with the categories we used today and she was the one to essentially decide which stars go into which categories I wish we named it after her because you should give credit where to the to the main person who came up with the ideas and also it would have been it could have had a really cool name okay so um what her name is is Annie jump cannon like her first name is Annie her her middle name is jump and her last name is cannon like the kind that shoots so the Annie jump cannon this could have been called the Annie jump cannon classification and I would have been so happy to call it that the the jump cannon classification but because of that I'm not gonna call it the Henry Draper classification okay I'm just gonna call it spectral type because that's that's what they call that's what the people working on it called at the time oh and yeah actually Annie jump cannon never got married never had kids she devoted her life to astronomy and made all kinds of other discoveries along with this so she is now astronomers now know who she is and and we give her credit for a lot of things now and there's plenty of women in an astronomy now and it's increasing all the time and they are given credit for what they do because that's what you do that's what you're supposed to do so yeah anyway I just wanted to put that as an aside because I kind of thought that was a was a crappy thing that the past did so what can you do anyway so let's talk about these spectral types Annie jump cannon x' spectral types how many are there turns out you can divide stars into just seven categories okay and this is not gonna show up because of the way the screen is gone let me see can i zoom this in a little bit no show me a bit show me bigger show me a bit whatever okay it's okay I don't worry about the eggs being able to actually see these but if you look here if you look real close these seven rainbows represent the seven spectrums that stars can have and they are in order okay they're in order if you look on here if you look from the top really closely to the bottom you can see how this one on the bottom has a lot more lines on it a lot more missing colors and the one on the top is only missing a few colors they've organized them so that those basically gradually increase as you go down the page here and later they were able to figure out that the order of the spectral types is the order of temperatures so the very hottest stars that exist all have spectrums that look like this and the very coldest stars that exist have spectrums that look like this and every other one in between is a medium is an intermediate temperature so that one's hotter than this one that one's hotter than this one that one's hotter than this one on down okay unfortunately these spectral types were labeled with letters and they were given a letter before they knew there was an order and they were also given letters before we knew there was only of them and when they reordered them according to temperature they kept the original letters so you can't see it here very well but the very hottest category is oh and the very coldest category is called M okay and everything else in between is a different letter so let me write out what those are from hot to cold so here we go the spectral types from hot to cold got hot over here and cold over here are in this order Oh B a F G K m OB a F g/km okay and you do need to know the order of these letters because here is a possible type of test question I could ask here you go answer this in the chat what's hotter a B or a G which one of these is hotter B is hotter okay which one's hotter an F or a K which one's hotter F because this side is the hot side this is the cold side so I could ask you any set of letters and ask which one's hotter okay now check this out here we go here's a slightly harder question what color would we expect the O's and bees to look what color would these O's and B Stars be those would be blue those would be blue okay how about these k's and elms what color would these k's and m's be those would be red that's right so O's and B's are blue because they're hot Ches and Elms are red because they're colder and then a F and G these ones in the middle what kind of colors would they be they would be yellow and orange depending on exactly where they they show up our Sun based on its surface temperature is a G our Sun our spectral type is a G star so even G's are yellow so think of these ones in the middle is yellowish these ones is red maybe a little bit orange on the case and then the O's and B's would be blue okay now somebody asked where do the letters come from originally they didn't know there was only seven categories they had a whole bunch of categories and they just labeled them ABCD efg on what oh no you know to the end of the alphabet and then they realized that some of them were duplicates so they got rid of some of the letters if they were a duplicate of another letter and then when they found out that there was a temperature order to it they rearranged the categories without real evering them honestly if it was me I probably would have real entered them as just ABCD efg or whatever right but I'm not I wasn't in charge of it if they had renamed it it would have been hard to to compare work that was done before and after the renaming like if you have renamed it at some point old papers that talked about bees wouldn't be the same be as later so that's why I think why they kept the same land letters but luckily for you guys there is a helpful phrase that has been used for probably over a hundred years to remember the order of these letters I did not come up with this phrase I think it's too goofy it's I apologize here we go here's the phrase oh by the way that's the word Oh for the letter oh I think that's kind of lazy the word they use for the letter O is oh okay so here we go here's the full phrase Oh be a fine girl kiss me yeah okay this is the phrase we use Oh be a fine girl kiss me not my phrase it's a you can tell it's super old-fashioned at this point and also you would be surprised how long it took people to realize that you could also go it's equal opportunity you can also go oh be a fine guy kiss me boom still works so no matter what you want to kiss it'll work as long as what you want to kiss starts with a G so Oh be a fine girl kiss me Oh be a fine guy kissed me works out o be of fine giraffe kiss me o be a fine goat kiss me o be of fine gerbil kiss me whatever it is as long as it starts with a G you're good yay yay so uh here we go feel free to come up with your own phrase if you want to that's totally fine I will never forget this phrase number one because it's extremely cheesy and number two when I first learned about this it was in the early 2000s and Snoop Dogg was real still real big um I know he's still big but he's not big like he was sorry snoop uh if you're watching this Snoop sorry you're still big to me okay but uh here we go why am i bringing up Snoop you guys know who snoop is right you guys you guys know who snoop is right okay good if you don't know who snoop is just just just get out of here just just get out of my class if you don't know who snoop is sorry about that so here's why I'm bringing him up when I was first taught this phrase Oh be a fine girl kiss me when the professor said it in my head immediately instead of my professor saying it it was snoop saying it with the with with with a much smoother rhythm so what I want you to do is right now I'm not gonna do a voice but I want you to imagine snoop saying this Oh be a fine girl kiss me with a better rhythm than that Oh be a fine girl kiss me probably slower and he would probably throw in some words in there that we probably shouldn't say on stream but oh be a fine girl kiss me Oh be a fine girl kiss me just turn it into a pop in your head and then you'll be you'll be good to go does that make sense okay all right almost