Here is a list of some of the methods astronomers use to measure distances:
Main sequence cluster fitting
Type 1a supernovae
Cepheid variables
Radar
Hubble's Law
Parallax
For the following objects, which of the above distance measurement methods do you think would be the best method to use?
1. The Andromeda Galaxy (a galaxy in the Local Group)
2. The Pleiades Star Cluster in the Milky Way
3. The Virgo Supercluster (a nearby cluster of galaxies, outside of the Local Group)
4. Mars
5. Alpha Centauri (nearby star)
6. The Leo Cluster (a galaxy cluster beyond the Virgo Supercluster)
Now think about how each distance measurement method is used to calibrate subsequent methods. Answer the following (somewhat challenging) questions!
(2a) If it was discovered that all of the clocks ever used to time a radar pulse to Venus ran too slowly (that is, measuring times to be shorter than they actually are), would that mean that Cepheid variable stars are more or less luminous than we have previously assumed? Explain.
(2b) If it was discovered that Cepheid variables are intrinsically dimmer (less luminous) than scientists have previously concluded, then are galaxies that are measured via Type 1a supernovae more or less distant than scientists have previously concluded? (NOTE: this hypothetical is independent of Part a; that is, in this part we are assuming that Cepheid variables are less luminous, but that may or may not be the correct answer for Part a.)
