... Four types of galaxy environments are considered: clusters, centers of groups, other places in groups, and the field. ... In order to check whether the mean ages of the stellar populations depend on environment density monotonically, as the hierarchical par­ adigm predicts, in this work I consider four types of environment separately: the cluster galaxies, the brightest (central ) galaxies of groups, the second­ranked group members, and the field galaxies. ... Group center SB(rs)0# 204 637 1996 Oct ...

... Go to This section of the glossary . ... APHELION : The point in a planet's orbit where it is farthest from the sun. ... It melts at 83.95 K, and boils at 87.45 K. Many people don't realize that argon makes up a full 1% of our atmosphere, while carbon dioxide is only a fraction of a percent of our atmosphere. ... COMET: An object moving about the sun in an eccentric orbit and composed of materials which, on warming up near the sun, form a "tail" which always points away from the sun. ...