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Presenting the Sky from North Georgia May 15, 2020 Part 1 Video Transcipt

We're looking at the night sky from here in North Georgia. This is on May 15th in the evening just after sunset around 9:00 p.m. We're facing north we see a sky filled with stars the stars form patterns on the sky that are leading us to areas called constellations. Constellations have defined borders. They're kind of like States on a map. Anywhere you point on a map of the United States you point within the borders of a state and anywhere a point on the sky we point within the borders of a constellation. These are the borders of the constellations that are up now. It's bright patterns of stars in each area that act as the landmarks so that we can find a constellation in the sky. Our first constellation is high in the real sky and our view here it's sort of in the middle of our screen and it's very famous constellation you may know of as the Big Dipper. We look for the Big Dipper by looking for four stars that make a cup and three stars that form a handle. Now it's part of a larger constellation called Ursa Major. Ursa just means bear so it's the Big Bear. We see here the Big Dipper in the Big Bear is just sort of part of the bear including his strangely long tail, but that curved tail can actually help us find another constellation in the sky. If we follow the handle of the Big Dipper we can actually arc to Arcturus. It's a bright orange star in a constellation called boaties and we look for boaties by looking for a sort of kite shape that's gonna be coming down off of Arcturus in our view here. I'll put up an outline and a picture so we can see that a little better boaties is a person. He's known in Greek and Roman mythology as the Ox driver, or herdsmen. So in a lot of Greek and Roman stories Ursa Major there is a bear but in some of the stories instead of being a bear the stars that form the Big Dipper, the seven stars of the cup and the handle, are actually oxen they're pulling a plow and they're being driven by a boaties here across the sky. The field that they're plowing is the entire northern half of the sky. Basically as the Earth turns we will see these stars rise in the eastern half of the sky and set in the western half of the sky so they sort of circle around the northern side of the sky and they're circling around a specific star the North Star. So the North Star is called Polaris and we look for it by looking for that Big Dipper seeing the cup of the Big Dipper. The end two stars of the cup, the ones that I refer this to the left right now, they point and they're pointing right now down or to the north at the North Star. They're called the pointer stars so the North Star Polaris would be sort of near the center bottom of our screen right now and it's always leading us north because Polaris is right above the North Pole of the earth. So that star everything is appearing to turn around it as the Earth spins and that's including the Big Dipper Ursa Major and boaties. Now Polaris is actually leading us to the Little Dipper. It is the end of the handle of the Little Dipper. We find the North Star first and then there are two very faint stars that form the then the rest of the handle and then four faint stars forming a smaller cup. I'll put up the outline so we can see it the Little Dipper is much fainter and harder to find in the sky than the Big Dipper. So we usually use the Big Dipper to point us to the North Star first and the Little Dipper is leading us to Ursa Minor which is the little bear again with a strangely long tail and the Big Dipper is also seen as a bear in some other cultures as well. There's different cultures around the world.They all have their own constellations and for several Native American tribes these stars were also a bear or sometimes a bear being followed by three hunters. And that was the three stars in the handle of the Big Dipper. Now we think that many different people saw these stars as a bear because as the star circle around the sky they change their orientation and bears are one of the few animals that are known for standing on four legs as well as standing up on two legs.  And so sometimes in the year the Big Dipper would appear to stand on end and perhaps remind people of a bear. There are many galaxies located around the Big Dipper and Ursa Major. These are galaxies that can be seen with a small telescope or maybe a pair of binoculars. I'll put up the position for one of them we're gonna look at it's called m101. We're gonna take a closer look at it by zooming in on this galaxy kind of like we're looking at it through a telescope. We have telescopes at University of North Georgia. They're at our Observatory, which is about four miles off campus to get away from city and campus lights. However, it's closed right now and that's mostly because we're constructing a new building. So there's a new building being built out there right now that’s gonna house bigger telescopes so definitely check their Facebook page for updates on when it's finished, when we might reopen later in the year and the Facebook page is under North Georgia astronomical observatory. But in the meantime here in the planetarium we're going to zoom in on 101. So here we see m101 much closer up. We see this galaxy it's a spiral galaxy that means it has a flat disk made out of clouds of gas and dust and stars flat like a pancake. It's the same type of galaxy as our own Milky Way. We see this galaxy face on here so we're seeing the spiral arm patterns across the disk of the galaxy those spiral arms are actually a density wave so it's basically a wave traveling through the clouds compressing the gas, making it denser along the spiral arms and that's where new stars will be born and 101 here is 21 million light years away. A Lightyear is how far light travels in one year so that means the light we see here took 21 million years to travel to us through space. We didn't always know the distances to galaxies. In fact we didn't even know there were other galaxies. Telescopes used to not really be able to pick out individual stars in these galaxies. They look like fuzzier patches in the sky and so we thought they could be smaller clouds of gas inside our own Milky Way. In fact we've only known the size of the universe how far away some of these galaxies are for about a hundred years or a bit less. There was a great debate a hundred years ago on April 26, 1920 between astronomers who were arguing this point: How big is the universe? Are these galaxies in the Milky Way or outside? And it was between two astronomers, Herbert Curtis and Harlow Shapley. And Curtis basically thought the universe was giant and that they were far away distant galaxies but Shockley thought the universe was a more reasonable size that these were clouds small clouds within the Milky Way and it would turn out from evidence found a few years later that the universe is gigantic, much bigger usually than we can even imagine and that these are distant galaxies outside of our Milky Way. Who actually was the first to figure that out while we attributed to Edwin Hubble he measured and recorded some distances to stars inside a galaxy called the Andromeda galaxy so not m101. Here I'm gonna bring up a picture of Andromeda so we can see that galaxy. It's actually the closest major galaxy to ours and that still puts it at two-and-a-half million light years away. So here we're seeing the Andromeda galaxy we're not seeing quite as face-on of a galaxy but it's still a spiral galaxy with a flat disk and Edwin Hubble looked at some stars in this galaxy called Cepheid variable stars so these are stars that pulse. They change their brightness at a very regular rate and that rate that they pulse at actually tells us how bright the stars are close up. If we know how bright they are close up then we basically can figure out how far away they are when we look at them in the sky and this is what Evan Edwin Hubble did. He figured out and measured the distance to the Andromeda galaxy. The relationship that he used basically how we know that Cepheid variables pulse at a rate that matches their brightness. That actually came from a different astronomer woman named Henrietta Swan Leavitt and that's a really important way to measure distances that we still use today. Now we're actually going to zoom away from the m101 here and bring down the picture of Andromeda and we'll talk about a few more things in the sky…

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