Explain why stellar parallax cannot be used to measure the distance to other galaxies.

1. a) Astronomers use the parallax method to measure the distance to nearby stars, but

we can’t use it to measure the distance to stars in other galaxies. Why not? Why isn’t the

parallax method useful for measuring the distances to stars in other galaxies?

They are so distant that the parallax is too small to be measured since parallax varies

inversely with distance.

b) Instead of the parallax method, we use the standard candle method to measure the

distance to stars in other galaxies. In particular, we use the standard candle method to

measure the distances to Cepheid variable stars in other galaxies. What is special about

Cepheid variable stars that makes them useful for this purpose?

We can figure out their luminosities from their periods of variation. Then if we measure

their fluxes we can calculate their distances.

2. a) From what were the protons and electrons in your body made, and roughly when

were they made?

They were made from energy (or gamma rays) very soon after the big bang (in the first

second). 400,000 years later they got together to make hydrogen atoms.

b) From what were the carbon atoms in your body made, and where were they made?

They were not made in the big bang. They were made much later inside of stars or in

supernovae. They were made by fusion from lighter atoms.

3. Make two sketches of the Milky Way Galaxy, one an edge-on view and one a face-on

view, labeling the various parts of the galaxy.

You should have labeled the