Galaxies Island Universes

Copyright – Adam Block, KPNO

Hubble Tuning Fork

Ellipticals

Ellipticals Huge No gas. No dust. No young stars. Nothing but old stars. Random orbits.

M 87 Copyright – Anglo-Australian Telescope Board Copyright - HST

Hubble Tuning Fork

Copyright – Adam Block, KPNO

Spirals

Spirals Like Milky Way Disks and bulge. Young stars and old. Gas and dust. Stars forming. Stars dying. M81 and M82 – Copyright R. Gendler

M63 Copyright – S. Miyazaki, Suburu

NGC1365 Copyright – VLT

M31 The Andromeda Galaxy Copyright – Jason Ware Copyright – S. Miyazaki, Suburu M31 The Andromeda Galaxy Copyright – Jason Ware

M33 – Copyright NOAO

John P. Gleason M51 - Copyright HST

NGC 4314

NGC 891 – Copyright WIYN NGC 891 – Copyright J.C. Barentine, NOAO

Sombrero Galaxy – Copyright P. Barthel VLT M10 – copyright Credner and Kohle Sombrero Galaxy – Copyright P. Barthel VLT

NGC 4526

Irregulars

Groups

The Local Group

Clusters

The Virgo Cluster

The Hubble Deep Field

21cm Radiation Neutral hydrogen (HI) gives off radiation at 21cm. Milky Way HI emission – Copyright J. Dickey

Extragalactic HI Observe HI in other galaxies. Measure wavelength of 21 cm radiation. Get velocity away from us.

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.

Map the Universe Measure v Calculate d Find: Voids Walls Clusters

Homework #11 Read: Bennett Ch 21.1 – 21.4 Do Ch21: Review Questions: 1, 2, 8 Problems: 1, 4, 5