A collection of thousands and millions of stars is called a galaxy.
Supplementary
Quantification, although the collection process could be called data collection (just a guess :)
Vertex
an angle
rainbow
rainbow
It is called a beam.
The electromagnetic spectrum.
they are called UV, or Ultraviolet rays.
At collection of stamps is refered to as a stamp collection. They are frequently kept in albums. Philately is the name for the study and collection of stamps.
Anode Rays are called the canal rays as the cathode used is perforated and the anode rays pass through the holes or canals of The cathode opposite to the anode.
a collection of fish is called a school of fish
Gamma Rays
NO.the rays are just called rays
Collection of coins is called collection of cons only n there is no specific word for it. It is different from numismatics as numismatics is the systematic study of coins. Mere collection of coins cannot be called as numismatics.
Web page collection called a Website.