The Milky Way

Question 1

What is a galaxy?

Answer 1

Huge gravitationally bound collections of stars with very little else between them.

Question 2

What are the two small satellite galaxies that orbit the milky way?

Answer 2

The small and large magellanic clouds (the SMC and the LMC).

Question 3

Explain the appearance of our galaxy from Earth and why it appears this way.

Answer 3

• Large Milky band stretching across the sky.

- We are looking into the plain of our galaxy from one of its spiral arms.

Question 4

Describe the shape of the Milky Way.

Answer 4

barred spiral galaxy

Question 5

Where in the sky of the Northern Hemisphere can you find the Milky Way?

Answer 5

• In a line from Cassiopeia to Cygnus

- The galactic centre lies in sageittarius

Question 6

Describe the three main structural components of our Galaxy.

Answer 6

• A bulge surrounding the nucleus (black hole).
• The disk (Young stars, gas and dust / Four major spiral arms / Is 1-2kpc thick / 30kpc in diamete)
• The Halo (Globular clusters: dense groups of relatively old stars)

Question 7

Whereabouts is our solar system found in the Milky Way?

Answer 7

• One of the spiral arms

- 10kpc from nucleus

Question 8

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

Answer 8

Huge clouds of gas and dust that can block light.

Question 9

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

Answer 9

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