Author Question: Discuss the discovery of galaxies, and the scientific debate that led astronomers to identify them ... (Read 23 times)

nelaaney · **on:** Jul 27, 2018

Discuss the discovery of galaxies, and the scientific debate that led astronomers to identify them as distant clouds of billions of stars.

What will be an ideal response?

Question 2

A certain type of atom can only absorb certain wavelengths.

a. True
b. False
Indicate whether the statement is true or false

ebe · **Reply #1 on:** Jul 27, 2018

Answer to Question 1

In the middle 1800s, astronomers were first able to build telescopes large enough to see galaxies clearly. Due to their nebulous appearance and spiral shape, they were called spiral nebulae.There was disagreement over whether galaxies were within our own galaxy, or distant objects outside of our galaxy. Astronomical technology was not sensitive enough to resolve the issue until the early 1900's. In 1920, Edwin Hubble was able to use a telescope much larger than its predecessors and more sensitive photographic techniques to take more detailed pictures of galaxies.Hubble's images showed individual stars in nearby galaxies. More importantly, Cepheid variables could be seen, and their period measured. The measurement of the period of the Cepheids allowed astronomers to calculate their distance, which was clearly outside of the Milky Way.

Answer to Question 2

True