ASTRON 1F03 Lecture Notes - Lecture 14: Minute And Second Of Arc, Stereopsis, Logarithmic Scale
18 Dec 2015
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Document Summary
Fair comparison: sun and other stars at the same distance. At the distance of a typical close star, the sun is ordinary (just another faint yellow star). We need to be able to measure distance to stars. Our brains compare views of the left and right eyes to get nearby distances. As earth orbits the sun, nearby stars change their positions against the background stars: comparing the position six months apart yields the distance. Parallax: change in position caused by a change in the position of the observer. The only direct way to measure the distance to a star is from the parallax. The greater the parallax, the smaller the distance. Parsec: distance at which parallax is one arcsecond: 1/3600 of a degree, 1 parsec = 3. 26 light-years. Long side of a triangle with short side 1au and angle 1 arcsecond.
