"Sergio" wrote in message news
Andrew wrote:
https://apod.nasa.gov/apod/image/1808/heic1404b1920.jpg

Here we see spiral galaxy ESO 137-001 hurtling through a
galaxy cluster called Abell 3627, which is about 220 million
light years away from us. As the spiral galaxy speeds along at nearly 7
million kilometers per hour, some of its gas and dust is being stripped
away, as we can see here.



very nice picture,

question, in a 'compact' cluster, how far apart are the stars in the
cluster ? just a guess is fine, I have tried to find that via internet

It is traveling through a galaxy cluster rather than a star cluster.

The stars in the foreground are from our galaxy.