Where is Andromeda galaxy now?

[Polchey]

I have a question. When we look into deep space at the Andromeda galaxy we are looking at it back in time as it was 2 million years ago because of the time it takes for light to reach us. Since that time to the present the Andomeda galaxy has moved a bit through space. It is said M31 is drifting towards the Milky Way. So then I wonder how much closer is M31 to the Milky Way now than it was 2 million years ago? Does anyone know?

[Ynjevi]

I have a question. When we look into deep space at the Andromeda galaxy we are looking at it back in time as it was 2 million years ago because of the time it takes for light to reach us. Since that time to the present the Andomeda galaxy has moved a bit through space. It is said M31 is drifting towards the Milky Way. So then I wonder how much closer is M31 to the Milky Way now than it was 2 million years ago? Does anyone know?

Milky Way and Andromeda galaxy near each other at a speed of 100 km/s. The distance between galaxies have shortened in 2 million years by about 670 light years, that is 0.3% of the current distance. At that speed it takes about 5-6 billion years these galaxies to collide. However, it is not known how straight Andromeda is nearing us so these values are far from accurate.

[Polchey]

100 k/s isn't very fast in cosmic terms. The speed of light moves much faster than that.

[Pierebean]

But I thought that galaxies moved away from each other? I thought that more a galaxy was far, more it moved quickly?

[Ynjevi]

But I thought that galaxies moved away from each other? I thought that more a galaxy was far, more it moved quickly?

Galaxies belonging to same groups or clusters orbit and collide with each other. Only more distant galaxies recede due to the cosmic expansion, because it is so weak.

[selden]

Over very large scales, galaxies are separating. However, many galaxies are in gravitationally bound clusters: the member galaxies orbit one another. The various clusters are separating from one another, though.

The Milky Way and the Andromeda Galaxy are members of what's called The Local Cluster, and happen to be travelling on paths that eventually will intersect.