Topic 4.1 - The Milky Way

Question 1

What is a galaxy?

Answer 1

Stars are grouped in huge gravitationally-bound collections called galaxies (with very little else between them)

Question 2

When we observe the galaxy, where are we looking?

Answer 2

Into the plane of our galaxy where most stars are located

Question 3

Name one of our closest galactic neighbours?

Answer 3

The Andromeda Galaxy

Question 4

How far away is the Andromeda galaxy from us?

Answer 4

700 kpc

Question 5

What are the three main components of the structure four galaxy?

Answer 5

1. The disc
2. The bulge
3. A halo

Question 6

Describe the disk.

Answer 6

The disk contains young stars, gas, dust and sites of star formation in four major spiral arms. The solar system is in one such arm, about 10 kpc from the nucleus

Question 7

What is the diameter and thickness of the disk?

Answer 7

Diameter- Roughly 30 kpc

Thickness- 1-2 kpc

Question 8

Describe the bulge.

Answer 8

It surrounds the nucleus and astronomers now believe that there is a massive black hole at the centre

Question 9

Describe a halo.

Answer 9

Contains mostly globular clusters which are dense groups of relatively old stars, in a spherical distribution around the galactic centre

Question 10

Apart from stars, what do the spiral arms of the Galaxy contain?

Answer 10

Huge clouds of gas and dust that can block light

Question 11

How can we see the structure of the spiral arms if light is being blocked by the clouds of dust and gas?

Answer 11

Microwave EMR (wavelength =21cm, frequency = 1420mHz) can be seen by radio telescopes on Earth. This wavelength is given off by hydrogen. Doppler shifts in the wavelengths We can work out how the galaxy is rotating