What is the angular diameter of star Deneb in degrees? And what is the diameter of Deneb in kilometer?

Deneb is a supergiant star who's angular diameter can be measured directly on the sky to be 0.002 arc seconds. It's actual diameter is about 200 times that of the sun. Please show me your working out. ThanksWhat is the angular diameter of star Deneb in degrees? And what is the diameter of Deneb in kilometer?Deneb is about 14.7 x 10^15 km from us, and has a diameter of 155 million km. That means that the angular diameter is:

155 x 10^6 / 14.7 x 10^15 = 0.0105 x 10^-6 radians



In degrees, that is 0.0105 x 10^-6 x 180 / pi = 0.604 x 10^-6 degrees

In arc-seconds, that is 0.604 x 10^-6 x 60 x 60 = 0.0022 arc-seconds.



The formulas you need are these:

angular diameter (in radians) = size / distance

angle in radians = angle in degrees x pi / 180

1 degree = 60 arc minutes

1 arc minute = 60 arc seconds