Many people most famously fred hoyle objected to this

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Unformatted text preview: se is expanding! Many people (most famously Fred Hoyle) objected to this idea Hoyle) He derisively referred to the idea as “the Big Bang” and the name stuck The Ultimate Distance Indicator Distance Measure a spectrum spectrum Get a redshift redshift Use Hubble’s Use Law and get a distance! distance! Active Galaxies Active Typical galaxies are just the sum of the Typical parts: parts: The total light from several billion stars The What does this imply? Active Galaxies Active Stars are: Nearly black bodies Surface temperatures in the thousands: peak emission as visible light peak Narrow spectral lines Narrow Many stars together collectively still look similar Many to this to Active Galaxies Active Stranger galaxies Stranger have been found: have Thousands of times brighter than usual brighter Most of the light is in the radio Active Galaxies? Active These galaxies look almost normal in the visible the There is something extra going on going There are several types: There Seyfert Galaxies, Radio Galaxies and Galaxies, Quasars Quasars Seyfert Galaxies Seyfert Mildest kind of active galaxy Mildest Discovered by Carl Seyfert, Seyfert 1943 1943 Like a normal Spiral Galaxy BUT BUT 1000x as much light as usual coming from the nucleus (the very centre of the galaxy) very Seyfert Galaxies Seyfert Nucleus The Seyfert galaxy nucleus: The Seyfert Emits mostly radio and infrared light Emits Emits up to 10 times the light of the entire Milky Way Has broad spectral lines indicating rapid motions motions Seyfert Galaxies Seyfert What is in the nucleus? The light output varies rapidly: less than one year than The source must be less than one light less one year across year (Galaxies are 10,000-100,000 light 100,000 years in size) years Seyfert Galaxy Nucleus Seyfert Extreme Speeds (1000 km/s) Extreme Small region Small Huge energy output Huge … sounds like a black hole Radio Galaxies Radio Radio galaxies were often first detected as radio sources as Unlike Seyferts, they have huge radio Seyferts they emission from a large area emission Radio Galaxies Radio Two main types: Core-Halo Core Lobes Lobes Radio Galaxies: Radio Core Halo Radio emission: Bright central core Radio + Visible Nucleus sized: less than one light year Nucleus 1037 Watts output 10 Large extended halo Large Galaxy sized: e.g. 150,000 light years Galaxy Fainter Fainter Radio Galaxies Radio Jets often detected leaving the core leaving Radio jets inside M87 giant Radio elliptical galaxy elliptical Easiest to see in Radio and Easiest Infrared Infrared Radio Galaxies: Radio Radio Lobes Some radio galaxies have a two sides lobed structure structure Most of the emission comes from the lobes rather than the core rather Centaurus A Radio Galaxies: Radio Radio Lobes Radio Lobes: Enormous size: 3,000,000 light years Enormous Up to 1038 Watts (10 Milk...
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