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How does the altitude of Polaris change?. We 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.
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We 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.
Through 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.
As 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!!!
We are going to deal with this problem by arriving at each location at precisely the same time…through our superstellar supersonic time machine (SSTM)!
Our first stop is really close by! Central Park in New York City!
New York, New York 41o N Latitude Big Dipper Cassiopeia Polaris Pointer Stars
We 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.
70 New York, New York 41o N 60 Big Dipper Cassiopeia 50 Polaris 40 30 Pointer Stars Measure the altitude of Polaris 20 10 0
What does this view “feel like” in 3-dimensions? POLARIS The arc represents the Celestial hemisphere (the sky above) E 41o HORIZON N S W The ground There 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.
Now let’s head to Tampa, Florida and view the night sky there!
70 Tampa, Florida What is the altitude of Polaris in Tampa? (Use the pointer stars of the Big Dipper) 60 50 40 30 20 10 0
What is the altitude of Polaris in Tampa? Again, let’s draw it in 3-D on the celestial sphere diagram!
70 Tampa, Florida Did you notice that the Big Dipper, and Cassiopeia are also lower in the sky here… 60 50 40 30 20 10 0
70 New York, New York 41o N …than in New York! 60 50 40 30 20 10 0
Now we are flying off to Popayán, Colombia in order to view the tropical night sky!
70 Popayán, Colombia 60 What is the altitude of Polaris in Popayán? 50 40 30 20 10 0
What is the altitude of Polaris in Popayán? Again, let’s get a feeling of what this looks like in 3-D!
Predict where you would find Polaris if you were at the Equator (Oo)
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!
Before, we measure, determine this: Are we North or South of NY? Here is NY again for comparison…
New York, New York 41o N Latitude And now back to our mystery location!
70 O.K.! Let’s determine the altitude of Polaris… 60 50 40 30 20 10 0
So where is Polaris in this location? The arc represents the Celestial hemisphere (the sky above) E HORIZON N S W The ground So now we know what latitude we are at. What is it?
Of the choices given, where in the world are we? Churchill, Canada Quebec City, Canada Hartford, CT Washington, D.C. New Orleans, LA
Now that you’re so good at this, predict the altitude of Polaris at the North Pole!
Let’s imagine what it would be like to do this at the North Pole. Be careful you don’t strain your neck! …and make sure you are EXTRA good while you are here!!!! You know who’s watching….
80 70 60 50 40 30 20 10
80 70 60 50 40 30 20
90 80 70 60 50 40
90 80 70 60
What is the altitude of Polaris? 90 80 70 60
All aboard for our last stop! Another mystery location for you to solve!
To give you a hint, we’ll place a marker where Polaris would be if we were in New York at this time… Do the measurement…
60 50 40 30 20 10 0
