Question

>How close would pre-stellar nebula of radius 200 AU have to be in order to have the same angular diameter as the 6 degree diameter of the Andromeda Galaxy as seen from earth? Calculate the apparent magnitude of the central star if it had a luminosity 10 times that of the sun.

Answer 1

1)

$D=\frac a{\sin\frac{6°}2}=3821~AU,$

2)

$\lg\frac L{L_0}=0.4(M_0-M),$

$M=2.5.$