4.1 Our Galaxy - 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

A giant disk shaped Catherine Wheel rotating around a central bulge.

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 diameter
The Halo
Globular clusters (dense groups of relatively old stars)
Spherically distributed along the galactic centre

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.
This wavelength is given off by hydrogen.
Doppler shifts in the wavelengths
We can work out how the galaxy is rotating

Question 10

Tell me about the closed model of the universe

Answer 10

If there’s a lot of mass - above critical density, universe slows down and collapses on self

Ends in Big Crunch

Question 11

Tell me about the flat universe model

Answer 11

If just enough mass in universe, universe expand forever but slower and slow - tend towards stoping never stop expanding

Question 12

Well me about the open universe model

Answer 12

If NOT enough mass, expand at steady rate forever

End in big yawn also Coles heat death or cold death - universe will become close to absolute 0

Question 13

What’s the density of the universe at the moment

Answer 13

Possibly exactly or very close to critical density - could go either way WOAH EXCITING AHH