The supergiant star Betelgeuse has an angular diameter measured to be 0.044 arcsecond. It’s
distance is measured to be 427 light-years. What is the diameter of the star Betelgeuse?
First lets convert the measured distance to kilometers.
427 light-years 9:46 1012 kilometers
= 4:04 1015 km
and arcseconds to degrees
= 1:22 10??5 degrees
The equation relating distance to angle is
angular size =
d physical size
solve this for the physical size to get
Physical Size d = D
360 = 1:22 10??5 4:04 1015
= 8:62 108 km
0r more than 600 times the size of the sun.
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