(1a) The Celestial Sphere
apparent rotation and the special role of the pole star.
Part of a high school course on astronomy, Newtonian mechanics and spaceflight
by David P. Stern
This lesson plan supplements the web page listed below. Originally named "The sky above us", it was split into two parts, each of which now has a lesson plan. This lesson covers the second of the two:
"The Celestial Sphere," section #1a : on disk Scelsph.htm, on the web
Goals: The student will|
Terms: East, west, south, north, horizon, equinox, winter solstice, summer solstice, elevation of the Sun )above the horizon). Celestial sphere, constellation, zodiac, celestial pole, the Pole Star ("Polaris"), celestial equator, rotation of the Earth, planets [theodolite, equatorial axis].
Stories and extras: Psalm 19 (A poetic impression of the sky)
Start the class with a discussion of the night sky: how many have seen the sky on a really dark night, away from streetlights and with no Moon? What was it like?
What is a constellation? Ask the class: did anyone recognize some constellations? Did you see the Big dipper? The Little Dipper? (Both featured in the next lesson plan) Orion? Cassiopeia?
If students have seen the Pleiades: could they count its stars? Tidbit: In Japanese, the Pleiades are called "Subaru." Next time you see a "Subaru" car, check its factory's logo--it has a picture of the constellation. How many stars on it?
[For the teacher: you might want to look up the web page "The Black Hole at the Center of our Galaxy".]
Has anyone visited a planetarium show? What was it like?
After this, present the material. The questions below may be used in the presentation, the review afterwards or both
--What is "the celestial sphere"?
We know better now, stars are actually very far away, and the Earth is the object that rotates. Still, the celestial sphere remains a convenient tool for describing the positions of the stars in the sky.)
--Are the positions of the stars on the celestial sphere fixed with respect to each other?
--At night, how do stars appear to move, and why?
--What do you know about the Earth's rotation around its axis?
--How long does it take the Earth to make a full rotation around this axis?
--When viewed from above the north pole, does the Earth rotate clockwise or counterclockwise?
One may explain that "clockwise" and "counterclockwise" is relative, it depends on the place from which one views the motion--it is not something absolute. Viewed from the far south, the Earth seems to rotate clockwise.
--What makes the Pole Star special?
--Do all stars set?
--Can any star visible from Earth, be seen from the US?
--What happens if you aim a telescope at a star and hold the telescopes direction fixed?
[Note: The book "First Light" by Richard Preston describes how astronomers at the 200-inch telescope on Mt. Palomar--for many years the largest in the world--deliberately clamped down the telescope, to make it sweep across long strips of the sky, searching for distant galaxies. A recommended, well-written book by a writer who spent some months living with the astronomers at the observatory.]
--What is an equatorial mounting?
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Author and Curator: Dr. David P. Stern
Mail to Dr.Stern: audavstern("at" symbol)erols.com .
Last updated: 27 August 2004