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GalaxiesGalaxies
Island Universes
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Copyright – Adam Block, KPNO
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Hubble Tuning Fork
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Ellipticals
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Ellipticals
• Huge• No gas.• No dust.• No young
stars.• Nothing but
old stars.– Random
orbits.
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M 87 Copyright – Anglo-Australian Telescope Board
Copyright - HST
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Hubble Tuning Fork
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Copyright – Adam Block, KPNO
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Spirals
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Spirals
• Like Milky Way• Disks and
bulge.• Young stars
and old.• Gas and dust.• Stars forming.• Stars dying. M81 and M82 – Copyright R. Gendler
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M63 Copyright – S. Miyazaki, Suburu
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NGC1365 Copyright – VLT
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M31 The Andromeda Galaxy Copyright – Jason Ware
Copyright – S. Miyazaki, Suburu
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M33 – Copyright NOAO
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M51 - Copyright HST
John P. Gleason
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NGC 4314
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NGC 891 – Copyright J.C. Barentine, NOAO
NGC 891 – Copyright WIYN
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Sombrero Galaxy – Copyright P. Barthel VLT
M10 – copyright Credner and Kohle
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NGC 4526
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Irregulars
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Groups
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The Local Group
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Clusters
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The Virgo Cluster
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The Hubble Deep Field
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21cm Radiation
• Neutral hydrogen (HI) gives off radiation at 21cm.
Milky Way HI emission – Copyright J. Dickey
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Extragalactic HI
• Observe HI in other galaxies.
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Rotation Curves
• If HI gas is rotating or moving, the 21cm radiation will be Doppler Shifted.
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Galaxy Masses
• Apply Kepler’s Laws to galaxy pairs.• Get estimates of mass.• Result: more dark matter.• Apply Kepler’s Laws to galaxy clusters.• Get mass estimates.• Result: even more dark matter!
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Hubble’s Law
• Measure the velocity of every galaxy.
• Nearly all are redshifted.
• Use Cepheids to measure distances to nearby galaxies.
• Result: The faster it’s moving, the farther away it is.
DH v
distance velocity
o
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Map the Universe
• Measure v• Calculate
d• Find:
VoidsWalls
Clusters