ASTR 101 Lecture 8: Earth, and Intro to Moons and Planets
28 Sep 2016
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As we move, distance changes by less than 0. 0004% for closet star (even less for more remote stars) Earth moves in space as fast as travelling from kingston to montreal in 10 seconds. We can use radar fun in space; we send radar signals to the moon, planets, astroids, to work out their distances and speed. Not to stars thought; very distant (returning signal would take way too long) and return signal would be too weak. We don"t need radar; light from stars itself contains info for us to work out state of relative motion. Stellar aberration: when using telescope, tip it forward to catch the ray of light. Stellar parallax: because of earth orbiting, we should see nearby star appear to shift relative to the background. Triangulation: using trigonometrical mathematics to calculate how far the stars are. Heliocentric parallax: using trig from using sun, star, and earth to make triangle to.
