Author Question: Describe qualitatively how the formation of deuterium and its current abundance is related to the ... (Read 53 times)

genevieve1028 · **on:** Jul 27, 2018

Describe qualitatively how the formation of deuterium and its current abundance is related to the critical density of the universe.

What will be an ideal response?

Question 2

What do the orbits of Populations I and II stars tell us about the formation of the Milky Way?

What will be an ideal response?

adf223 · **Reply #1 on:** Jul 27, 2018

Answer to Question 1

Since stars tend to destroy deuterium, it is assumed that all existing deuterium is primordial. Also, the higher the density of the universe, the more matter is around for the deuterium to react with, so high density means small quantities of deuterium and vice versa. This allows an independent measure of the density of the universe, and reveals that the hadronic (protons and neutrons) mass of the universe is only about 3 of the critical density.

Answer to Question 2

Older Population II stars move in comet-like orbits, well above the plane of the Galaxy in the spherical Halo. The Population I stars formed later, after most of the remaining gas and dust had settled down into a disk, flattened by the rotation of the condensing Galaxy. Their orbits are much more like those of planets, fairly circular and in the galactic plane.