Apr15 - GALAXY FORMATION Elliptical galaxies also built up...

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Unformatted text preview: GALAXY FORMATION Elliptical galaxies also built up by merging smaller galaxies GALAXIES OFTEN COME IN CLUSTERS Perseus Cluster (300 million ly) Coma Cluster (320 million ly) Virgo Cluster (60 million ly) Galaxies are preferentially in clusters and along filaments THE FIRST QUASAR: 3C 273 • First found as a radio source • Only a faint weird ‘star’ at position of radio source • Maarten Schmidt in 1963: Spectral lines shift by huge amount – Doppler shift ! Going away at 15% of speed of light! – Hubble’s Law ! 2 billion light years away! – Inverse Square Law ! 10 12 L " ! More luminous than whole galaxies! • Dorrit Hoffleit in 1963: Looked at brightness history on old Harvard pictures – 3C 273 at roughly same brightness back to 1880’s ! not an explosive phenomenon – 3C 273 varied on time scale of weeks ! Must be smaller than light-weeks in size • DILEMMA: How can 3C 273 pack the energy generation of galaxies into something as small as our Solar System??...
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Apr15 - GALAXY FORMATION Elliptical galaxies also built up...

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