WEBVTT 00:20.086 --> 00:21.354 align:left position:22.5%,start line:89% size:67.5% Finding the North Star 00:21.454 --> 00:23.790 align:left position:12.5%,start line:89% size:77.5% JAMES: Welcome to Star Gazers. 00:23.890 --> 00:27.193 align:left position:75%,start line:83% size:15% I'm James Albury, director of the Kika Silva Pla Planetarium in Gainesville, Florida. 00:27.293 --> 00:31.631 align:left position:77.5%,start line:83% size:12.5% DEAN: And I'm Dean Regas, astronomer from the Cincinnati Observatory, and we're here 00:31.731 --> 00:33.967 align:left position:80%,start line:89% size:10% to help you find you way around the sky. 00:34.067 --> 00:39.005 align:left position:72.5%,start line:83% size:17.5% JAMES: If someone asked you right now to name the brightest star we can see in the sky what 00:39.105 --> 00:40.006 align:left position:32.5%,start line:89% size:57.5% would you say? 00:40.106 --> 00:41.007 align:left position:32.5%,start line:89% size:57.5% DEAN: The Sun! 00:41.107 --> 00:42.175 align:left position:25%,start line:89% size:65% JAMES: That s true. 00:42.275 --> 00:44.911 align:left position:77.5%,start line:83% size:12.5% You re going to be technical today, aren t you? 00:45.011 --> 00:48.381 align:left position:77.5%,start line:83% size:12.5% Buuuuut what about the brightest star you can see in the nighttime sky? 00:48.481 --> 00:51.918 align:left position:75%,start line:83% size:15% DEAN: If you re thinking of Sirius out there folks, you're right. 00:52.018 --> 00:54.821 align:left position:77.5%,start line:83% size:12.5% But if you said the North Star you're not so right. 00:54.921 --> 00:58.925 align:left position:72.5%,start line:83% size:17.5% But don't feel bad if you said the North Star, because most people believe that the North 00:59.025 --> 01:04.230 align:left position:72.5%,start line:83% size:17.5% Star is the brightest star, when in fact there are about 50 other stars visible to the naked 01:04.330 --> 01:05.932 align:left position:20%,start line:89% size:70% eye which are brighter. 01:06.032 --> 01:09.702 align:left position:72.5%,start line:83% size:17.5% So why do so many people think the North Star is the brightest star? 01:09.803 --> 01:14.507 align:left position:72.5%,start line:83% size:17.5% JAMES: Well, one reason might be that so many people have heard so much about the North 01:14.607 --> 01:19.546 align:left position:70%,start line:83% size:20% Star that they assume it must be the brightest, when in fact it is really the most important 01:19.646 --> 01:23.850 align:left position:77.5%,start line:83% size:12.5% star, at least as far as sailing the seas, flying a plane or traveling from place to 01:23.950 --> 01:24.884 align:left position:42.5%,start line:89% size:47.5% place. 01:24.984 --> 01:26.686 align:left position:30%,start line:89% size:60% Let's show you. 01:26.786 --> 01:30.390 align:left position:77.5%,start line:83% size:12.5% JAMES: O.K., we've got our skies set up so that we're facing due north any night this 01:30.490 --> 01:33.927 align:left position:22.5%,start line:83% size:67.5% week around 9:30 p.m., where you should easily be able to find the 01:34.027 --> 01:35.728 align:left position:35%,start line:89% size:55% Big Dipper. 01:35.829 --> 01:39.466 align:left position:77.5%,start line:83% size:12.5% Those 4 stars that make its cup and the 3 stars that make its handle are so distinct 01:39.566 --> 01:41.234 align:left position:27.5%,start line:89% size:62.5% in the spring sky. 01:41.334 --> 01:44.471 align:left position:80%,start line:83% size:10% DEAN: And if you want to find the North Star for yourself, all you have to do is use 01:44.571 --> 01:50.210 align:left position:77.5%,start line:83% size:12.5% the two stars at the end of the cup, which are appropriately called, the pointer stars. 01:50.310 --> 01:54.347 align:left position:77.5%,start line:83% size:12.5% All the boy scouts and girl scouts in the audience know this trick already, but when 01:54.447 --> 01:57.817 align:left position:17.5%,start line:83% size:72.5% you shoot an arrow through them and continue that line down and to the 01:57.917 --> 02:01.554 align:left position:75%,start line:83% size:15% left the pointer stars will always point you to the North Star. 02:01.654 --> 02:05.859 align:left position:72.5%,start line:83% size:17.5% JAMES: Now once you've found it, you'll notice the North Star is about the same brightness 02:05.959 --> 02:07.560 align:left position:22.5%,start line:89% size:67.5% as the pointer stars. 02:07.660 --> 02:11.331 align:left position:77.5%,start line:83% size:12.5% So since the North Star doesn t stand out, why is it so important? 02:11.431 --> 02:16.736 align:left position:75%,start line:83% size:15% JAMES: Well I'll give you a clue: the North Star is also called Polaris because it is 02:16.836 --> 02:19.672 align:left position:72.5%,start line:83% size:17.5% the closest bright star to the north celestial pole. 02:19.772 --> 02:21.841 align:left position:87.5%,start line:89% size:2.5% DEAN: So what? (you may be asking) 02:21.941 --> 02:26.179 align:left position:77.5%,start line:83% size:12.5% JAMES: Welllll, this simply means that if we could stand at the north pole, the North 02:26.279 --> 02:31.151 align:left position:77.5%,start line:83% size:12.5% Star, Polaris, would be directly overhead, which further means that it is directly above 02:31.251 --> 02:33.019 align:left position:27.5%,start line:89% size:62.5% the Earth's axis. 02:33.119 --> 02:36.823 align:left position:77.5%,start line:83% size:12.5% DEAN: Now if you think of the Earth's axis as a huge nail we could insert it at the south 02:36.923 --> 02:41.227 align:left position:75%,start line:83% size:15% pole and it would go all the way through the Earth and come out the north pole and extend 02:41.327 --> 02:45.965 align:left position:75%,start line:83% size:15% out into space; that nail, the Earth's axis, would point to the North Star. 02:46.065 --> 02:48.101 align:left position:85%,start line:89% size:5% JAMES: So what? (you may be asking) 02:48.201 --> 02:53.473 align:left position:75%,start line:83% size:15% DEAN: Wellllll, This also means that as the Earth turns on its axis, all the stars in 02:53.573 --> 02:59.379 align:left position:70%,start line:83% size:20% the heavens would seem to move except one...The star directly above the Earth's axis, Polaris 02:59.479 --> 03:00.580 align:left position:30%,start line:89% size:60% the North Star. 03:00.680 --> 03:03.249 align:left position:65%,start line:89% size:25% That's why Polaris, the North Star is so important. 03:03.349 --> 03:08.621 align:left position:72.5%,start line:83% size:17.5% JAMES: You see, Polaris is the only star which remains stationary in the heavens while all 03:08.721 --> 03:11.357 align:left position:80%,start line:89% size:10% the other stars slowly circle around it. 03:11.457 --> 03:16.663 align:left position:70%,start line:83% size:20% It is always due north, so before the invention of the compass, this star was extremely important 03:16.763 --> 03:19.799 align:left position:65%,start line:89% size:25% to navigators and explorers to determine direction. 03:19.899 --> 03:23.937 align:left position:77.5%,start line:83% size:12.5% DEAN: In fact, if you're lost at night and don't know which direction you're headed, 03:24.037 --> 03:29.142 align:left position:70%,start line:83% size:20% simply find the Big Dipper, then use the pointer stars to find the North Star and for as long 03:29.242 --> 03:33.079 align:left position:77.5%,start line:83% size:12.5% as you live, the North Star will always be due north. 03:33.179 --> 03:36.583 align:left position:72.5%,start line:83% size:17.5% And if it's not, you're either on a different planet, like Mars 03:36.683 --> 03:40.720 align:left position:72.5%,start line:83% size:17.5% whose North Star is Deneb, the tail of Cygnus the Swan.... 03:40.820 --> 03:43.389 align:left position:77.5%,start line:83% size:12.5% JAMES: Or you could be on Earth, but in a different century. 03:43.489 --> 03:47.293 align:left position:77.5%,start line:83% size:12.5% You see, Polaris won't always be our North Star. 03:47.393 --> 03:51.598 align:left position:75%,start line:83% size:15% The Earth's axis slowly wobbles in a motion we call precession. 03:51.698 --> 03:57.971 align:left position:77.5%,start line:83% size:12.5% This slow wobble takes about 26,000 years to complete, moving 1 degree every 72 years. 03:58.071 --> 04:02.375 align:left position:72.5%,start line:83% size:17.5% So, 3000 years ago, Polaris wasn't considered the pole star. 04:02.475 --> 04:07.347 align:left position:77.5%,start line:83% size:12.5% And in 14,000 years, the bright star Vega, in Lyra the Harp, will be our pole star. 04:07.447 --> 04:09.082 align:left position:35%,start line:89% size:55% DEAN: Hmmm 04:09.182 --> 04:13.419 align:left position:80%,start line:83% size:10% I guess in 14,000 years Polaris won t be the North Star and will have to change its 04:13.519 --> 04:14.420 align:left position:42.5%,start line:89% size:47.5% name. 04:14.520 --> 04:15.421 align:left position:35%,start line:89% size:55% Until then 04:15.521 --> 04:19.521 align:left position:22.5%,start line:89% size:67.5% BOTH: Keep looking up!