Posted by Kaitlyn on .
Explain the idea of parallaz. The closet star to the Sun, Proxima Centauri, is 4.2 light years away from us. What is its parallax angle?

Astronomy 
drwls,
The parallax angle, in radians, is the ratio of the Earth orbit diameter to the stellar distance. It is the size of the angle that the stellar position changes relative to stars much farther away, during the course of a year.
Read this for a good review:
http://www.astronomy.ohiostate.edu/~pogge/Ast162/Unit1/distances.html
Earth orbit diameter = 160*10^6 km (approx)
Proxima Centauri distance = 4.0*10^13 km
Angle = 4*10^6 radians = ____ arc seconds 
Astronomy 
Kaitlyn,
Thank you for your help!