|Last: 11. Origin of the Elements||Next: 13. The Realm of the Nebulae|
|Ch. 11-1||The Mikly Way is only one among billions of galaxies|
|Ch. 11-2||Studies of Cepheid variable stars led to the discovery of the distances to other galaxies|
|Ch. 11-3||Discovering the universe helps us understand our place in it|
|Ch. 11||THE STRUCTURE OF OUR MILKY WAY GALAXY (p. 230)|
|Ch. 11-4||Interstellar dust hides the true extent of the Milky Way|
|Ch. 11-5||Radio observations help map the galactic disk|
|Ch. 11-6||The galaxy is rotating|
|Ch. 11||MYSTERIES AT THE GALACTIC FRINGES AND NUCLEUS (p. 236)|
|Ch. 11-7||Most of the matter in the Galaxy has not yet been identified|
|Ch. 11-8||The galactic nucleus is also still poorly understood|
|Ch. 11||TYPES OF GALAXIES (p. 239)|
|Ch. 11-9||The winding of a spiral galaxy's arms is correlated to the size of its nuclear bulge|
|Ch. 11-10||Self-propagating star formation and spiral density waves produce spiral arms|
|Ch. 11-11||Bars of stars run through the nuclear bulges of barred spiral galaxies|
|Ch. 11-12||Elliptical galaxies display a variety of sizes and masses|
|Ch. 11-13||Hubble represented galaxies with different shapes in a tuning fork diagram|
In this photograph looking south from the Big Island, the Milky Way stretches across the horizon.
These images show the entire sky. The Milky Way is the luminous band stretching horizontally across the pictures. Note the clouds of dust which create dark patches within the Milky Way. The IR image doesn't show these clouds since the dust is transparent to IR light; instead, this image reveals the disk and central bulge of our galaxy.
This is a computer simulation of a rotating disk galaxy. The disk is shown in blue, the central bulge in yellow-white, and the dark halo in red. As the galaxy spins, the camera pulls back to show the true extent of the dark halo.
This figure shows orbits in a galaxy like the Milky Way. Note that these orbits are not closed ellipses; Kepler's 1st law is not valid within a galaxy because the mass is spread out instead of concentrated at the center. The blue orbit is that of a typical disk star (Population I); it stays close to the disk plane. The red orbit is that of a typical halo star (Population II); the plane of its orbit slowly rotates.
A `globular cluster' is a swarm of about 106 stars held together by gravity. All the globular clusters in our galaxy are quite old (Population II); they are relics of the early stages of the Milky Way's formation.
`Open clusters' are younger (Population I) and smaller than the globular clusters shown above. In the Lagoon Nebula we see a gas cloud in which young blue stars are still forming. The Jewel Box Cluster is about ten million years old.
This movie shows the motion of stars near the center of the Milky Way over a period of eight years. From the observed motions of these stars we can infer the presence of a massive black hole in the center of our galaxy!
Homework 12: Finding Distances With Standard Candles, due 11/20.
Quiz 12: Structure of The Milky Way, given 11/15.
Last modified: November 19, 2001