with individual groups of galaxies rather than with the cluster as a whole.
Spectral analysis of this emission reveals that the intracluster gas has a relatively high proportion of ele- ments heavier than hydrogen and helium. Since heavier elements are known to be formed only through fusion processes that occur in the interiors of stars, and since the interiors of massive stars are spread into space by enormous supernova explosions, it appears that supernovae have been relatively common in the galaxies of this cluster.
The cluster is moving so quickly through space that it could not remain intact without more invisible or ΓÇ£darkΓÇ¥ matter than visible material.
