What do you know about: THE STARS?
Take This Quiz!
1) Name the closest star to Earth.
2) How many stars can we see in a typical night sky?
3) What is the name of the bright band we see in the Summer Sky?
4) What causes this bright band?
5) Why don't we see Stars during the day?
6) Do Stars live forever? Why (or) Why not?
Parallax
The DISTANCE is crucial to accurately determining characteristics of Stars (and just about everything). Consider the triangle above. If we know the baseline (orbital size of the Earth), and we measure the angle centered on the Star (the parallax angle), we can determine the distance using the small angle formula.
The Parsec. The distance of a star which subtends a PARallactic angle of one arcSECond over one Earth orbit. It is approximately 3.26 light years. Ancient Greeks knew enough geometry to test a theory that the earth goes around the Sun and to look for parallactic motion of the stars. They saw NONE and concluded the Earth stood still. However, the parallactic motion of even the closest stars is so small, it is simply unobservable with an unaided eye. The Earth IS moving, the stars are just much, much further than the Greeks could comprehend.