Calculating the radius of a HII region - worked out but just need you to check

[lavenderblue]

Homework Statement

Estimate the radius of a spherical HII region which rests at a distance of 500 pc that subtends an angle of 20' at the observer. [1'=3x10-4 radians]

Homework Equations

L=D(theta)

Where D is the distance, L is the angular size and theta is the angle.

The Attempt at a Solution

L= 500*20*3*10^-4 = 3pc

L=3pc

Radius = 1.5 pc

 

[Joffan]

Yes, as given, and to the likely limits of precision of the inputs. The 500pc distance in particular probably has ±50pc or more. So my instinct to quibble about how many radians in 1' isn't worthwhile :-).

 

[lavenderblue]

Thank you! :-)