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| Galaxies |
1. Spiral tracers must have short enough lifetimes that they can't move further from their place of birth in their lifetime than the width of a spiral arm. The Sun, and certainly any cooler main sequence stars, have lifetimes far too long to trace the spiral structure. For example, the Sun has had time since its birth to revolve some 20 times around the galaxy, crossing through spiral arms many times. Thus, it has long since left the spiral arm where it presumably was born. Even if red dwarfs did not live much longer than the Sun, they would also not be good tracers because they are faint and too difficult to see. But given their long lifetimes, that is not a significant point.
3. The key is the word "observed". The bright blue spirals are easier to see than the faint small ellipticals. But careful counts for more nearby regions where faint ellipticals are easier to see suggest that there are more of them out there (by a factor of about three) than spirals; we just can't see them at large distances.
5. We are not certain. Perhaps there is no clear distinction between dwarf ellipticals and large globular clusters.
7. We are not certain. They appear to be almost devoid of visible matter, but may well contain substantial dark matter.