Question

Describe a method to find out the size of a heavenly body.

Answer 1

Using the telescope if you will try to see any heavenly body such as moon, planet, etc then it will appear like a disc. Now we have to find the angle alpha made by the diameter of the planet at a point present on the earth’s surface. Let r be the distance of the heavenly body from the earth and D is the diameter of the body. So the formula will be:
 = D / r

Or it can be written as

D=r

If the far off star seems to be a small point in the telescope then this method will not be applicable.


Answer 2

Using the telescope if you will try to see any heavenly body such as moon, planet, etc then it will appear like a disc. Now we have to find the angle alpha made by the diameter of the planet at a point present on the earth’s surface. Let r be the distance of the heavenly body from the earth and D is the diameter of the body. So the formula will be:
 = D / r

Or it can be written as

D=r

If the far off star seems to be a small point in the telescope then this method will not be applicable.