last time we looked at one way of locating things in the sky the horizontal coordinate system how might we organize what we see up in the sky in general to help I've taken some snapshots with an observatory simulation program called stellarium at first glance we see a bunch of stars in the sky you might recognize the belt of a the head of Taurus and the Seven Sisters otherwise named the platis however how would you point that out to someone who's never looked up at the night sky before you might just wing it and say see those bright stars in the slightly diagonal line near the Horizon that's the belt of Orion now the belt is surrounded by four stars that make up a rectangle those are the shoulders and feet of Orion Orion also has a sword on his belt hanging down that's a good start what we've described is called a constellation a constellation is just a pattern of stars in the sky the stars don't have to be related to each other and in the vast majority of cases the stars that we use to denote a constellation are not at all related if we look up to the right from the right shoulder of Orion we see the V of Taurus the Bull one of the horns of the bull has a bright red star this is one of these cases where the prominent stars of a constellation are certainly related to each other these are the brightest stars of a star cluster called the hiades further up into the right we see the pladis otherwise named the Seven Sisters this is a real cluster of stars and because the cluster's appearance looks like a tiny cup with a handle we call its readily identifiable shape an asterism the belt of Orion is an asterism the V of Taurus is both part of a constellation and an asterism asterisms can span across many constellations or they can be so small as to need a telescope to see them again both constellations and asterisms are named patterns of stars in the sky that do not have to be related to each other all constellations and asterisms are products of our place in space if we went a thousand light years away from here we'd not be able to pick out any of the familiar shapes except possibly those that are directly behind us and even those would be heavily distorted I've just now added the artwork associated with these various constellations this artwork is based on Western mythologies a lost work of Hotes known by the summary done by aristes said that Orion was the son of the sea god Poseidon and U daughter of Minos king of creit one day Orion was hunting on the island of creit with the goddess Artemis during the hunt for some reason Orion threatened to kill every beast on Earth Gaia was horrified and sent a giant scorpion to kill Orion the creature succeeded in its Mission and after his death the goddesses asked Zeus to place Orion among the constellations Zeus consented and as a memorial to the hero's death added the Scorpion to to the heavens as well as the constellation Scorpius Orion as a constellation seems to be hunting Taurus the Bull and he's seemingly backed up by the Unicorn monoceros he's followed by his dog in the lower left highlighted by Sirius the dog star the dog Kanis major seems to be chasing the rabbit at his feet there are all these kinds of little stories you can tell by imagining that these dogs and heroes and animals are up in the sky many other cultures also called Orion a great hunter or giant notably The Babylon Ians called Orion the true Shepherd of Anu in Kuna form tablets dating back to PR 3000 BC the ancient Egyptians from about the 23rd or 24th century BCE called Orion sa a god whose form Pharaoh would take when he ascended to the heavens the list goes on but the current star names of Orion hail from medieval Muslim astronomy that there are stories and myths and legends placed upon the patterns of stars in the sky says so much about Humanity's need need to connect to the Everlasting and unchanging it is easily argued that religious thought has its roots in noting the permanence of the Stars patterns year after year compared with the frighteningly temporal nature of life on Earth it's also a personal belief of mine that as we lose our Dark Skies to light pollution we lose a significant part of what it means to be human we lose our sense of things bigger than ourselves and we lose our connection to the journey that is represented by watching the sunset the slowly appearing stars in the darkening Sky arise to tell their stories remind us of ancient times and times that will be as the sun rises this alternate reality recedes into the realm of Dreams the striking difference between Day and Night Calls for us to create these stories and learn from them to help us understand the ancient stories better I've trace the constellations with lines that denote the most prominent asterisms this connect the dots game helps us better see the patterns I've also added the constellations names now I've added some names for some of the brightest stars Al debron is the name of the eye of the bull Beetlejuice is the upper left shoulder as we see it of a riot on the right is Bellatrix the advancing foot is named Riel the knee he's resting on is SEF and the belt stars are named alnac Alam and Mina you can see Sirius in the lower left and proon and canis minor in the upper left most bright stars are named many have Arabic names which have been formally adopted by the international astronomical Union this is partly in honor of the fact that Muslim astronomers kept the knowledge of ancient Greek astronomy alive in the European Dark Ages by translating talmy's syntaxis Mathematica into Arabic as the almagest later translations hundreds of years later back from the Arabic allowed Western astronomers the opportunity to use improved measurements of the positions of stars and planets to eventually prove that the Earth orbited the sun Al deon's name came from the Arabic Al dearon meaning the follower because it seems to follow the pladis the name Beetle Jews was derived from the Arabic yadal jaza The Hand of Al jazza I.E Orion an error in the 13th century reading of the Arabic initial yah as ba eventually led to the European name Sirius hails from ancient Greek which translates into the scorcher we could go on and I suggest you look up the star names on Wikipedia little tidbits are really interesting many traditional names have been used for centuries across cultures it seems that the sky is a great meeting ground for people I've removed the art so we can just show the lines and some star names it's fun to draw them out for a friend when you're at an evening stargazing session might go a little like this do you see the belt stars of Orion they're the three in a row close together all the same brightness good now from the left most one of the belt goes straight up 12:00 to the bright red star that's Beetlejuice about the belts width to the right at 4:00 from Beetlejuice is a bluish star that's Bellatrix those two stars are the shoulders of Ryan the hunter if you look in between those stars and a bit up you see a brightish star that's not as bright as Bellatrix but is the third brightest right around there that's MSA The Shining one in Arabic that and that's the head of Orion so let's go now back to to the Belt the belt has something right below it the sword of Orion the Middle star in the sword is pretty fuzzy and doesn't quite look like a star that's the distant star forming region called m42 or the great nebula in Orion if we go just down to the right from The Sword we see a bright star almost as bright as Beetlejuice but it's blue that star is Riel on the left foot of Orion we're assuming he's facing towards us so that'll be his left foot his right foot is named SEF which is interesting in because SEF in Arabic means sword swords get moved around I guess it's chats like these that happen at every Star party across the planet that people teach others the names and traditions of the sky however such Stars don't help us with a myriad of other stars in the sky so what's their story in 1922 at the request of the IU during its very first session Henry Norris Russell produced a list of 88 constellations but these constellations didn't have clear borders between them then in the next IU session in 1928 Belgian astronomer Eugene delport Drew up a definitive list of boundaries for the 88 constellations he used vertical and horizontal lines of right Ascension and declination to cover the entire celestial sphere these modern constellations usually shared the names of their Greek and Roman predecessors such as orah and Taurus those boundaries are what you see as the dim red lines in this image any star planet or nebula that is in that area of the sky is by definition in that constellation so now it's not just the lines and asterisms it's everything inside the red boundaries let's now take a look at one of those Star Charts from the international astronomical Union as you can see from the website on the left this is where you can look at all the official ones this particular star chart is published by Sky and telescope and in on behalf of the IOU and what we see on the boundaries are of course across the bottom and top you have the right Ascension which is the boundaries that are vertical and we have the declination which is the horizontal boundaries the declination is given in tens of degrees and the right Ascension is given hours so what we see is we see the boundary of Orion going around it's bordered in white it has the familiar asterisms in it as well as numerous Stars what's a little different about this star chart that you might notice is across the bottom the magnitudes are defined a star's magnitude is how bright it is so zero magnitude is like the second one from the left the brightest star is minus 2 magnitude which would be pretty bright Sirius is the brightest star in the sky so it lies just between minus1 and min-2 magnitude the faintest stars are magnitude six that you can see with your naked eye in a very dark location so this star chart reveals only those Stars down to roughly magnitude six on the chart we see there's also proper names on there we see the green lines that DeMark the aster RM we also see Greek letters which are the Bayer designations and sometimes we have a number by it so it's like Omron 1 and Omron 2 or Pi 1 Pi 2 pi 3 Pi 4 Pi 5 and Pi 6 but we also have little squares which are nebuli and so forth and as you see in this zoomed in view there's the names of the stars Beetlejuice has a secondary ring on it which means that it's a variable star and we also see some yellow little fuzzy patches those things are clusters of stars as well essentially all the major things that you might want to do are typically located on such Star Charts as well professional astronomers use these Star Charts too uh just to make sure they know where they are in the sky and now I'm just going to show you an example from a different pair of constellations Ursa Major and Ursa Minor these are very familiar constellations in the sky uh notably the Big Dipper and the Little Dipper and and the Big Dipper is highlighted by called Ursa Major which is the big bear and the Little Dipper is the little bear and if we zoom out and look at them in the larger size scales in the sky we can see how these constellations relate to the Stars around them so let's use Ursa Major to help us summarize this entire set of ideas we've been talking about Ursa Major is the name of the constellation The Familiar asterism is the Big Dipper and you can kind of see it highlighted with the Bolder green lines the rest of the traditional constellation is highlighted by the green lines which are dimmer than the main asterism lines but the IU accepted boundaries for the entire Constellation Are the vertical and horizontal lines that ride along the uh right Ascension and declination lines those are the official boundary for the constellation the constellations of course filled with stars and it looks like we've got some new things in there there are galaxies M101 the PIN and the interacting pair m81 and M82 as well as the planetary nebula m97 so these are some of the major objects in Ursa Major that can be seen down to say roughly magnitude 6 or seven or so m81 82 and 101 and 97 are dimmer than magnitude 6 but we put them on there because they're relatively famous things to go try to find in a small telescope speaking of which what are some free resources that you can use to have Star Charts so you can go outside and look for things in the sky well a good place to start are the monthly maps that are provided by NASA's jet propulsion laboratory through their night sky Network these maps are created by the astronomical league and you can go get them at these website that's shown here what you get in this thing is a full sky map that shows all the way around where you're look assuming that you're kind of lying on your back looking straight up at the Zenith and with your feet pointed towards the south in this map we can see where Orion is we can see where the Big Dipper is there's a bunch of other asterisms out there and there's other things that you can go poke around and look for in fact this is a great way to begin and it's probably your best start to go out with naked eye observing just going outside and seeing what's up in the sky and taking a piece of paper with you don't take your phone because your phone will give you night blindness and you won't be able to see the stars if you look at the bright light coming out of your phone all right so there's a bit about constellations and asterisms keep looking up in the sky