FORM B 1. Slide 6 shows galaxies that are billions of parsecs away.
Astronomers have difficulty studying the structure of the Milky Way Galaxy.
RR Lyr variables stars cannot be used to measure the Hubble Constant. A G main sequence star, an M main-sequence star, an RR Lyrae star, and a Cepheid variable star all have the same apparent magnitude. An elliptical galaxy may be formed. All the interstellar gas is lost from both galaxies. Many of the stars within the galaxies collide and go supernova.