How do astronomers measure the diameter of the sun?

1 Answer
Dec 8, 2016

Please see below.

Explanation:

One of the easiest way to measure diameter is to use a pinhole camera. But, for this you need a very small hole in, say, a card. This is not easy, but what you can do is to make a bigger whole say #3# #cm.# wide square or a circular hole.

Now a paste a metal film covering it completely. You can use a aluminium foil for this. Now create a very tiny hole in it and place it in sun to form an image as shown below.
enter image source here
Now measure the diameter of image. (better make image on a centimeter graph for accuracy). Also measure the distance of image from pinhole.

The diameter of sun can then be calculated as follows:

#Diametercolor(white)(x)ofcolor(white)(x)sun#
enter image source here

Note that finer the pinhole and larger the distance between pinhole and image, higher the accuracy in measuring diameter.