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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