Answer: 1.1818^37 kg
Step-by-step explanation:
Given that:
Orbit speed = 1300 km/s
Radius (r) = 18 light days
Mass of object the star is orbiting :
Using the relation :
M = rv² / G
Where ; r = Radius in m ; v = velocity in m/s
G = 6.67 * 10^-11 = gravitational constant
18 light days in meters = 4.662 * 10^14 m
v = 1300km/s to m/s
v = (1300 * 1000)m /s = 1300000 m/s = 1.3 * 10^6 m/s
Hence ;
M = (4.662 * 10^14 * (1.3 * 10^6)^2 / (2/3) * 10^-10
M = (4.662 * 10^14) * (1.69 * 10^12) / (2/3) *10^-10
M = (7.87878 * 10^26) / 6.67 * 10^-11
= 1.1818^37 kg