In the center of our galaxy
from 1992 through 2003
astronomers were able to observe
a star, orbiting compact radio source
The star had an orbit with average radius
and period 15 years.
From this information astronomers estimated
the mass of Sagittarius A.
v = 2π(1.4x1014)/(15x365x24x60x60) = 1.86x106 m/s
a = (1.86x106)2/(1.4x1014) = 0.0247 m/s2
0.0247 = (6.673x10-11)M/(1.4x1014)2
M = 7.24x1036 kg
7.24x1036/(1.989x1030) = 3.6 million suns!
Astronomers infer that Sag. A is a
supermassive black hole
(it cannot be seen)!
OH LITTLE STAR