The astronomers use trigonometry
for calculating distances to stars. They know the diameter of the
Earth’s Orbit which is 2 A.U.(Astronomical Unit). They find out the
parallax angle by simply taking two photographs in January and then again
6 months later, when the Earth has changed it’s position in space
by an amount equal to the diameter for the Earth’s diameter. They
use accurate telescopic equipment to measure the parallax angle.
The formula for determining the distance
is as follows:
Length of Arc
= Angle
Circumference of Circle
360'
AB = 2p
2 Pi r 360'
r = 360' AB
2p 2 Pi
since 1' = 3600 arcseconds
and AB = 2 A.U.
Therefore,
r = 1296000 * 2 A.U.
2(3.14) 2p
r= 206265 A.U.
p
since 1 parsec = 206265 A.U.
Therefore,
r = 1
p
where r is the distance
and p is the parallax angle
Units
The parallax angle is measured in arc seconds
1' =
3600 arc seconds
The distance is measured in parallax seconds
1 parsec
= 206265 A.U.
This page was created by Ahmed Javed.