<Ul> <Li> The star S2 follows an elliptical orbit with a period of 15.2 years and a pericenter ( closest distance ) of 17 light - hours ( 7013180000000000000 ♠ 1.8 × 10 m or 120 AU ) from the center of the central object . </Li> <Li> From the motion of star S2 , the object 's mass can be estimated as 4.1 million M , or about 7036820000000000000 ♠ 8.2 × 10 kg . </Li> <Li> The radius of the central object must be less than 17 light - hours , because otherwise , S2 would collide with it . In fact , recent observations of the star S14 indicate that the radius is no more than 6.25 light - hours , about the diameter of Uranus ' orbit . </Li> <Li> No known astronomical object other than a black hole can contain 4.1 million M in this volume of space . </Li> </Ul>
how many solar masses is the black hole at the center of the milky way
4.1 million