Topic 4.1 - The Milky Way 0.0 / 5 ? AstronomyOur Galaxy - The Milky WayGCSEEdexcel Created by: goldstar3Created on: 31-05-18 16:15 A) Appearance of the Milky Way Naked Eye: A band of light obscured in places by interstellar gas and dust. Runs along the galactic equator Binoculars: More individual stars. Runs through asterism of summer triangle Small Telescope: Many more stars and the band gets brighter nearer the centre of the Milky Way towards Sagittarius. 1 of 4 B) Observed Milky Way The observed Milky Way is the plane of our own galaxy The spiral arms we see are the plane We are in a spiral arm If viewed from above, the Milky Way would look like a Catherine Wheel 2 of 4 C) Features of our galaxy 30kpc diameter 1 - 2 kpc thickness We are 10kpc from the centre 2/3 of the way out from the nucleus (in a side-on view) The centre of the Milky Way cannot be seen by us due to interstellar dust A blake hole is believed to exist at the centre Sites of star formation in 4 major spiral arms The halo surrounding the nucleus contains globular clusters 3 of 4 D) 21cm Radio Waves Gas & dust is opaque to visible light Gas clouds contain hydrogen Emit EM radiation, wavelength 21cm Can penetrate the dust Detected by radio telescopes 'tuned' to this frequency Observed frequency of the waves is higher than 1420MHz from gas moving towards us & vice versa Astronomers use ^^^ differences to show the galaxy is rotating 4 of 4
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