Question

Why is stellar parallax important?

Answer 1

Stellar parallax is very important for approximating distances of stars from us.

Explanation:

Stellar parallax is the apparent angular displacement of a star, observed from two different known locations, in relation to the almost stationary star.

If `alpha` is the parallax for Radio Telescope observations ( from the surface of the Earth ) of the same star, in an exact interval of N days, the distance of the star from the observer is approximately
`sin(Ntheta/2)/sin (alpha/2)` AU ,
where `theta= 360/365.256363` deg.

1 ly = 62900 AU, nearly.