1. What is a galaxy?
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- Huge gravitationally bound collections of stars with very little else between them.
2. What are the two small satellite galaxies that orbit the milky way?
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- The small and large magellanic clouds (the SMC and the LMC).
On the following video, the Milky Way can be seen at 2 min 24 sec, the SMC and LMC between 2 min 30 sec and 2 min 39 sec and all three are clearly visible between 3 min 20 and 4 min.
http://youtu.be/wFpeM3fxJoQ
3. Explain the appearance of our galaxy from Earth and why it appears this way.
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- Large Milky band stretching across the sky.
- We are looking into the plain of our galaxy from one of its spiral arms.
4. Describe the shape of the Milky Way.
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- A giant disk shaped Catherine Wheel rotating around a central bulge.
5. Where in the sky of the Northern Hemisphere can you find the Milky Way?
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- In a line from Cassiopeia to Cygnus
- The galactic centre lies in sageittarius
6. Describe the three main structural components of our Galaxy.
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- 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
http://youtu.be/zKE4Bt8ylhM
7. Whereabouts is our solar system found in the Milky Way?
8. Apart from stars, what do the spiral arms of the Galaxy contain?
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- Huge clouds of gas and dust that can block light.
9. How can we see the structure of the spiral arms if light is being blocked by the clouds of dust and gas?
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- 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
