Question

1. Iron has the lowest mass per nuclear particle of any element. What does this mean for a star when it's core has filled with iron?
2. When observing galaxies you notice the following:

There tend to be more spiral galaxies for a given number of elliptical galaxies the farther away the galaxies are.

The closer elliptical galaxies tend to be larger and more massive than the far ones.

What does this suggest to us about how galaxies form?

3.Explain what we observe when we view galaxies at greater distances. Why does this happen?

Answer 1

1) Fusion reactions release energy only when the mass of the products is less than the mass of the reactants, so when the core of the star has filled with Iron, which has the lowest mass per nuclear particle, using energy fuel from fusion in no longer an option for the star.

2) This may suggest that elliptical galaxies are older and evolve (by merging) into spiral galaxies

3) When we observe distant galaxies we are actually looking back in time. This happens because they are so far away that the light leaving them would take millions (or even billions) of years to get to us