(ORDO NEWS) — Our Milky Way galaxy is one of two large galaxies that make up the so-called Local Group, which includes more than fifty galaxies.
The Andromeda Galaxy is the second large galaxy that is part of the Local Group and our nearest galactic neighbor; The Milky Way and Andromeda slowly revolve around each other.
The rest of the Local Group is mostly relatively small objects such as the Large and Small Magellanic Clouds (dwarf galaxies adjacent to the Milky Way), many of which are gravitationally bound to larger galaxies.
Milky Way and galactic movements
If you want to figure out how two objects will revolve around each other, you need to know their mass, their distance from each other, and their speed relative to each other.
The masses of two objects in this case, the Milky Way and Andromeda determine the region around which they will orbit. This area is called the center of mass or barycenter and is a point in space around which the masses of moving objects are evenly distributed.
For a system like the Sun and Earth , almost all of the mass is in the star, and the mass of a planet averaging 150 million kilometers away actually has little to no effect on the center of mass.
The Earth only slightly “pulls” the center of mass of the Earth-Sun from the center of mass of the Sun itself, so that for this system the barycenter practically coincides with the center of mass of the star.
But if two objects have similar masses and are at a great distance from each other, then the center of mass is somewhere between them, in a conditionally empty space.
The mass of Andromeda, 2,537,000 light-years from Earth, is estimated at 0.8-1.5 trillion solar masses, and the mass of the Milky Way is 1-2 trillion solar masses. Both objects are extremely massive and separated by a very long distance, but they are gravitationally bound to each other.
Because neither can escape the gravitational pull of the other, they orbit around a point somewhere in the middle of space between the Milky Way and Andromeda.
At this point – the center of mass between them – our Galaxy and Andromeda will eventually collide (the masses of the galaxies are still different, so one of them will win the tug of war one day). But don’t worry, this event is still about 4.5 billion years away.
Does the Local Group as a whole revolve around anything?
Yes, the Local Group is part of the Virgo Supercluster, which in turn is in motion relative to even larger structures in the Universe. After all, nothing in this world is at rest.
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