Question

1. What is the origin of the Cosmic Microwave Background? What is this evidence for?
2. We observe many irregular galaxies in the universe. What is the likely cause of irregular galaxies? What properties would we expect to see in an irregular galaxy?
3. Why are the spiral arms of spiral galaxies so bright compared to the rest of the galaxy? What are the arms thought to be?

Answer 1

a) Cosmic microwave background (CMB) is an almost-uniform background of radio waves that fill the universe. The CMB is the leftover heat of the Big Bang. At this time, the universe was filled with a hot, ionized gas. So the origin photons scattered off from electrons just as light is scattered through fog.This scattering produced a thermal or blackbody radiation spectrum that we observed.

This is the evidence of big bang. Because the spectrum observed is similar to the spectrum predicted by tbe big bang theory and no other theory is present which could say otherwise

B)Irrehular galaxies could be formed thro ugh interactions and mergers of other galaxies. They might might not have started as irregular but they interacted with each other and became distorted due to uneven gravitational force.

They could be passing by some other galaxy or they got merged with some other one.

Properties: They don't have any distinct shape, they are faint and hard to see than other spiral and elliptical galaxies. They have no distinct nuclear bulge or spiral arm structure. They contain born young and old stars and substantial gas and dust.

C) Spiral arms are bright because they have young blue stars because of the high mass density and the high rate of star formation, which make the arms so bright.

These spiral arms may contain a lot of gas and dust and younger stars that shine brightly before they die quickly