1 00:00:20,086 --> 00:00:21,354 Finding the North Star 2 00:00:21,454 --> 00:00:23,790 JAMES: Welcome to Star Gazers. 3 00:00:23,890 --> 00:00:27,193 I'm James Albury, director of the Kika Silva Pla Planetarium in Gainesville, Florida. 4 00:00:27,293 --> 00:00:31,631 DEAN: And I'm Dean Regas, astronomer from the Cincinnati Observatory, and we're here 5 00:00:31,731 --> 00:00:33,967 to help you find you way around the sky. 6 00:00:34,067 --> 00:00:39,005 JAMES: If someone asked you right now to name the brightest star we can see in the sky what 7 00:00:39,105 --> 00:00:40,006 would you say? 8 00:00:40,106 --> 00:00:41,007 DEAN: The Sun! 9 00:00:41,107 --> 00:00:42,175 JAMES: That s true. 10 00:00:42,275 --> 00:00:44,911 You re going to be technical today, aren t you? 11 00:00:45,011 --> 00:00:48,381 Buuuuut what about the brightest star you can see in the nighttime sky? 12 00:00:48,481 --> 00:00:51,918 DEAN: If you re thinking of Sirius out there folks, you're right. 13 00:00:52,018 --> 00:00:54,821 But if you said the North Star you're not so right. 14 00:00:54,921 --> 00:00:58,925 But don't feel bad if you said the North Star, because most people believe that the North 15 00:00:59,025 --> 00:01:04,230 Star is the brightest star, when in fact there are about 50 other stars visible to the naked 16 00:01:04,330 --> 00:01:05,932 eye which are brighter. 17 00:01:06,032 --> 00:01:09,702 So why do so many people think the North Star is the brightest star? 18 00:01:09,803 --> 00:01:14,507 JAMES: Well, one reason might be that so many people have heard so much about the North 19 00:01:14,607 --> 00:01:19,546 Star that they assume it must be the brightest, when in fact it is really the most important 20 00:01:19,646 --> 00:01:23,850 star, at least as far as sailing the seas, flying a plane or traveling from place to 21 00:01:23,950 --> 00:01:24,884 place. 22 00:01:24,984 --> 00:01:26,686 Let's show you. 23 00:01:26,786 --> 00:01:30,390 JAMES: O.K., we've got our skies set up so that we're facing due north any night this 24 00:01:30,490 --> 00:01:33,927 week around 9:30 p.m., where you should easily be able to find the 25 00:01:34,027 --> 00:01:35,728 Big Dipper. 26 00:01:35,829 --> 00:01:39,466 Those 4 stars that make its cup and the 3 stars that make its handle are so distinct 27 00:01:39,566 --> 00:01:41,234 in the spring sky. 28 00:01:41,334 --> 00:01:44,471 DEAN: And if you want to find the North Star for yourself, all you have to do is use 29 00:01:44,571 --> 00:01:50,210 the two stars at the end of the cup, which are appropriately called, the pointer stars. 30 00:01:50,310 --> 00:01:54,347 All the boy scouts and girl scouts in the audience know this trick already, but when 31 00:01:54,447 --> 00:01:57,817 you shoot an arrow through them and continue that line down and to the 32 00:01:57,917 --> 00:02:01,554 left the pointer stars will always point you to the North Star. 33 00:02:01,654 --> 00:02:05,859 JAMES: Now once you've found it, you'll notice the North Star is about the same brightness 34 00:02:05,959 --> 00:02:07,560 as the pointer stars. 35 00:02:07,660 --> 00:02:11,331 So since the North Star doesn t stand out, why is it so important? 36 00:02:11,431 --> 00:02:16,736 JAMES: Well I'll give you a clue: the North Star is also called Polaris because it is 37 00:02:16,836 --> 00:02:19,672 the closest bright star to the north celestial pole. 38 00:02:19,772 --> 00:02:21,841 DEAN: So what? (you may be asking) 39 00:02:21,941 --> 00:02:26,179 JAMES: Welllll, this simply means that if we could stand at the north pole, the North 40 00:02:26,279 --> 00:02:31,151 Star, Polaris, would be directly overhead, which further means that it is directly above 41 00:02:31,251 --> 00:02:33,019 the Earth's axis. 42 00:02:33,119 --> 00:02:36,823 DEAN: Now if you think of the Earth's axis as a huge nail we could insert it at the south 43 00:02:36,923 --> 00:02:41,227 pole and it would go all the way through the Earth and come out the north pole and extend 44 00:02:41,327 --> 00:02:45,965 out into space; that nail, the Earth's axis, would point to the North Star. 45 00:02:46,065 --> 00:02:48,101 JAMES: So what? (you may be asking) 46 00:02:48,201 --> 00:02:53,473 DEAN: Wellllll, This also means that as the Earth turns on its axis, all the stars in 47 00:02:53,573 --> 00:02:59,379 the heavens would seem to move except one...The star directly above the Earth's axis, Polaris 48 00:02:59,479 --> 00:03:00,580 the North Star. 49 00:03:00,680 --> 00:03:03,249 That's why Polaris, the North Star is so important. 50 00:03:03,349 --> 00:03:08,621 JAMES: You see, Polaris is the only star which remains stationary in the heavens while all 51 00:03:08,721 --> 00:03:11,357 the other stars slowly circle around it. 52 00:03:11,457 --> 00:03:16,663 It is always due north, so before the invention of the compass, this star was extremely important 53 00:03:16,763 --> 00:03:19,799 to navigators and explorers to determine direction. 54 00:03:19,899 --> 00:03:23,937 DEAN: In fact, if you're lost at night and don't know which direction you're headed, 55 00:03:24,037 --> 00:03:29,142 simply find the Big Dipper, then use the pointer stars to find the North Star and for as long 56 00:03:29,242 --> 00:03:33,079 as you live, the North Star will always be due north. 57 00:03:33,179 --> 00:03:36,583 And if it's not, you're either on a different planet, like Mars 58 00:03:36,683 --> 00:03:40,720 whose North Star is Deneb, the tail of Cygnus the Swan.... 59 00:03:40,820 --> 00:03:43,389 JAMES: Or you could be on Earth, but in a different century. 60 00:03:43,489 --> 00:03:47,293 You see, Polaris won't always be our North Star. 61 00:03:47,393 --> 00:03:51,598 The Earth's axis slowly wobbles in a motion we call precession. 62 00:03:51,698 --> 00:03:57,971 This slow wobble takes about 26,000 years to complete, moving 1 degree every 72 years. 63 00:03:58,071 --> 00:04:02,375 So, 3000 years ago, Polaris wasn't considered the pole star. 64 00:04:02,475 --> 00:04:07,347 And in 14,000 years, the bright star Vega, in Lyra the Harp, will be our pole star. 65 00:04:07,447 --> 00:04:09,082 DEAN: Hmmm 66 00:04:09,182 --> 00:04:13,419 I guess in 14,000 years Polaris won t be the North Star and will have to change its 67 00:04:13,519 --> 00:04:14,420 name. 68 00:04:14,520 --> 00:04:15,421 Until then 69 00:04:15,521 --> 00:04:19,521 BOTH: Keep looking up!