By combining new data from ESA's Gaia mission with observations made with Hubble, astronomers have found that the Milky Way weighs in at about 1.5 trillion solar masses within a radius of 129, 000 light-years from the galactic centre.
It turns out that the Andromeda galaxy is also going about 20 miles per second sideways. As a result, it will take a more winding path toward us, won’t arrive for another 4.5 billion years and won’t hit so hard, at least not at first
The collision could occur much earlier than the predicted impact between the Milky Way and another neighbouring galaxy, Andromeda, which scientists say will hit our galaxy in eight billion years. This could wake up Milky Way's dormant black hole.
Residing in the same part of the Milky Way galaxy like the solar system, the star is believed to be up to 13.5 billion years old which is evidenced by its extremely low metal content, reports Xinhua news agency
Black holes from outside the halo are believed to fall under the influence of the SMBH as they lose their energy, causing them to be pulled into the vicinity of the SMBH, where they are held captive by its force.