Question

How is the distance to a distant star calculated? Give an example.

Answer 1

There are several ways to measure stars distance. See below

Explanation:

If a star is "close" to Earth, it is possible to masure the angle to star in two postions of Earth: one around january `E_1` (when earth is closer to Sun) and other `E_2` in June (when earth is remote from the sun)

In these two positions we can build up a triangle `E_1SE_2` with a known distance `E_1E_2` and 2 angles measured. After we apply sinus and cosines theorems.

If a star is to much remote both angles measured are closer to 90 degress and this method doesn't work. In this case we apply the magnitude (real and aparent) of a star and apply the formula

`D^2=2.512^(n-M)xx100` where m is brightness, M luminosity and D the distance

M and M are measured with sofisticated material in observatories. There is an available table of relevant stars where M and m are known