Exploring Astronomy: Basics of the Celestial Sphere

1. Goal: To understand the very basics of Astronomy. Objectives: To understand how the night sky is set up To be familiar with some useful Astronomy terms.

2. Celestial Sphere • Imagine all of the stars and objects in the sky were painted on a single canvas • Each star/galaxy/ect has a specific spot on the celestial sphere

4. Basic Sky Terms • http://www.whfreeman.com/dtu5e/con_index.htm?01 • Celestial Sphere – if all night sky objects where on a hollowed sphere, this sphere is the Celestial Sphere. • Celestial N. and S. Poles, and Equator – expansions of the Poles and Equator of the earth. • On Celestial Sphere – position of Stars are constant! The sun, moon, and planets all move along this sphere.

5. Basic Sky Terms continued • Angel of Declination – think of this as the object’s Latitude on the Celestial Sphere. • Angle of Right Ascension – think of this as the object’s Longitude on the Celestial Sphere. • Ecliptic Plane – the plane which the sun and the planets trace as they move across the Celestial Sphere.

8. Useful Astronomy Terms (distance) • AU or Astronomical Unit = 93 million miles (distance from the earth to the sun). • 1 meter = 3.3 feet • 1 km = 1000 m = 0.6 miles • 1 cm = 0.01 m = 0.4 inches

9. More Useful Astronomy Terms • 1 kg = 1000 grams = 2.205 lbs on surface of the earth • 1 degree K (Kelvin) = 1 degree C = 1.8 degrees F = a unit of temperature • 32 F = 0 C = 273 K (freezing pt of water) • 0 K = absolute zero. • Speed of Light= 3 * 108 m/s = 1 lightyear / year

10. Conclusion: • We have examined the set up of the nighttime sky • We have examined the most common Astronomy terms that will be used in this course.