Author Question: If H equals 70 km/s/Mpc, then a galaxy with a radial velocity of 2100 km/s has a distance of ... (Read 92 times)

yoooooman · **on:** Jul 27, 2018

If H equals 70 km/s/Mpc, then a galaxy with a radial velocity of 2100 km/s has a distance of approximately

a. 2170 Mpc.
b. 2030 Mpc.
c. 30 Mpc.
d. 0.03 Mpc.
e. 147,000 Mpc.

Question 2

How does a gas cloud become hot?

What will be an ideal response?

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

Answer to Question 1

c

Answer to Question 2

Once the gas cloud begins to contract, gravity cause the atoms to fall toward the center, gaining speed as they go. This is known as free-fall collapse. By the time the atoms have fallen most of the way to the center of the cloud, they are traveling rapidly. The atoms begin to collide with one another and convert their inward motion to jumbled, random motion of thermal energy, causing the temperature of the gas to increase. When the contracting core becomes hot enough, it produces short-wavelength radiation to which the core is not transparent, then the core's thermal energy can no longer escape, making it even hotter.