8.13 How will you ‘weigh the sun’, that is estimate its mass? The mean orbital radius of the earth around the sun is 1.5 × 108 km.

Here,
r=1.5×108km=1.5×1011m
T=1year=365.25days=365.25×24×60×60s.
G=6.67×10-11Nm2kg-2
Wehave,
M=4π2r3GT2
=4×3.142×1.5×101136.67×10-11×365.25×24×60×602
=2×1030kg.