12

Angular
sizes

•Quite often we will need to find __linear size__ of
some object, given its __distance__ and its __angular size__

Note – the book leaves out the units of
“arcsec”. Do not make that mistake yourself.

An example different than the one in the book: How large is the sun?

The angular diameter of the sun is about 0.50. To convert that to
arcseconds use:

0.5 deg ´ 60 arcmin/deg ´ 60 arcsec/arcmin = 1800
arcsec

The sun is 1.5 ´ 108 km away (= 1
astronomical unit). So

From our text:
Horizons, by Seeds