2We will be taking a “virtual” field trip to different spots on the Earth and viewing the stars there.We are going to focus in on two major constellations, and one very important star—Polaris, or the North Star.
3Altitude: the angle of a celestial object above the horizon Constellation: group of stars that form a pattern and are used to help people locate celestial objectsLatuitude: angular distance north or south of the equator
4Through the magic of “virtual astro-vision,” we will be viewing the sky at the same time in every location we go to!We need to do this so that we can see the sky the same way at each location.
5As you may already know, our view of the constellations change over an evening—the stars appear to move because the Earth is rotating!****Your view of the sky at 9:00 p.m. is different from your view at 11:00 p.m., just for example.****Polaris is the exception to this!!!
6We are going to deal with this problem by arriving at each location at precisely the same time…through our superstellar supersonic time machine (SSTM)!
10New York, New York 41o N Latitude Big DipperCassiopeiaPolarisPointer Stars
11We are going to “calibrate” our screen so that we can make measurements of the location of Polaris in other places on Earth.We will be using a device called a “sextant.” This measures the star’s angle above the horizon. This is called ALTITUDE.This simulation is only in 2-D, so the sextant appears like a ruler. However, in the real-world of 3-D, this device would measure what angle you have to tilt your head up in order to see a star. Therefore, if the star is at the horizon, the angle is ZERO. Directly overhead, the angle is 90o.
12New York, New York 41o N Big Dipper Cassiopeia 70 60 50 40 30 20 10 Polaris4030Pointer StarsMeasure the altitude of Polaris2010
13What does this view “feel like” in 3-dimensions? POLARISThe arc represents theCelestial hemisphere(the sky above)E41oHORIZONNSWThe groundThere is a 41 degree angle between the horizon and Polaris.In other words, the viewer must tilt his or her head (and telescope!) up 41o from the horizontal in order to directly see Polaris.
1770Tampa, FloridaWhat is the altitude of Polaris in Tampa? (Use the pointer stars of the Big Dipper)605040302010
18What is the altitude of Polaris in Tampa? Again, let’s draw it in 3-D on the celestial sphere diagram!
19What does this view “feel like” in 3-dimensions? Plot the position of Polaris for TampaThe arc represents theCelestial hemisphere(the sky above)EHORIZONNSWThe groundIn Tampa, would you tilt your head up more or less than in New York in order to see Polaris?
2070Tampa, FloridaDid you notice that the Big Dipper, and Cassiopeia are also lower in the sky here…605040302010
2170New York, New York 41o N…than in New York!605040302010
25What is the altitude of Polaris in Popayán? 70Popayán, ColombiaWhat is the altitude of Polaris in Popayán?605040302010
26What is the altitude of Polaris in Popayán ? Again, let’s get a feeling of what this looks like in 3-D!
27What does this view “feel like” in 3-dimensions? Plot the position of Polaris for PopayánThe arc represents theCelestial hemisphere(the sky above)EHORIZONNSWThe groundIn Popayán, how would you have to orient your head so you could see Polaris?
29Predict where you would find Polaris if you were at the Equator (Oo)
30Let’s see if you are getting the hang of this Let’s see if you are getting the hang of this! For our next stop we are going to view the sky FIRST, and then predict our latitude from our view of Polaris!Pretty neat, huh!