<p>Dark matter was needed to give the stars in a spiral galaxy a cause of their speed. So they proposed there must be some extra dark matter in the Galaxy. The total extra mass of dark mater is quite high. As a consequence of that, the whole galaxy becomes much heavier. But in the group or a cluster, the Galaxy also has a speed relative to other galaxies. So my question is whether the mass needed to give the stars their speed is the same mass that is needed to explain its movement within its cluster or a group?</p>

CC BY-SA 3.0
2016-01-21T00:29:32.877Z
I'm not sure what you're asking.   Certainly the dark matter mass affects the relative speed of galaxies in our local group.
userLTK
CC BY-SA 3.0
2016-01-22T00:59:00.790Z
I'm understanding the question as whether the dark matter mass within the galaxies explaining the motion of individual stars is consistent with the motion of the whole galaxies in the galaxy cluster. I don't know the answer for sure, but I  think, there is needed additional dark matter outside the galaxies to account for the motion of the galaxies in the cluster.
Gerald
<milky-way><dark-matter>
Does the quantity of dark matter needed in the Milky Way to give the stars their speed compare with the speed of the Milky Way?
Marijn 
# Does the quantity of dark matter needed in the Milky Way to give the stars their speed compare with the speed of the Milky Way?

(Asked by: username_0 on 2016-01-20)

Dark matter was needed to give the stars in a spiral galaxy a cause of their speed. So they proposed there must be some extra dark matter in the Galaxy. The total extra mass of dark mater is quite high. As a consequence of that, the whole galaxy becomes much heavier. But in the group or a cluster, the Galaxy also has a speed relative to other galaxies. So my question is whether the mass needed to give the stars their speed is the same mass that is needed to explain its movement within its cluster or a group?

**Tags:** milky-way, dark-matter

> **Comments:**
> **username_1**: I'm not sure what you're asking.   Certainly the dark matter mass affects the relative speed of galaxies in our local group.  
> **username_2**: I'm understanding the question as whether the dark matter mass within the galaxies explaining the motion of individual stars is consistent with the motion of the whole galaxies in the galaxy cluster. I don't know the answer for sure, but I  think, there is needed additional dark matter outside the galaxies to account for the motion of the galaxies in the cluster.  

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