This page contains course information for the Summer Session offering of ASTR 348, Introduction to Cosmology. This class will also be offered in the Spring 1997 session.
This is a descriptive course covering some of the most exotic aspects of modern physics and astronomy: special and general relativity, black holes, the nature of space and time, the big bang. We begin with a history of humanity's understanding of the cosmos. We will show how understanding the construction of the universe is tied into understanding the physics of mechanics. We will talk about relativity and how Einstein's theories have changed the way that space and time are viewed. We will then move on to the expanding universe and the big bang model. Finally we will talk about the latest ideas in cosmology research.
The syllabus for this course can be accessed on the web. For further information about the astronomy department, go to its home page: http://www.astro.virginia.edu. You will also find links to other astronomical web resources there.
As a study aid, you can consult an outline of the textbook on the web.
Questions submitted by class members will be posted with answers. Think of this as a FAQ section (except that the questions may not have been asked frequently). I will try and post a few questions as they come in to me.
Interesting cosmology images shown in class will be placed here for your further viewing and study.
The universe is filled with galaxies. Everywhere one looks there are more and more galaxies. The galaxy m100 is an example of a spiral galaxy, here seen in a detailed Hubble Space Telescope (HST) image. Galaxies tend to occur in clusters, such as the Hercules cluster. If one were to study an apparently empty region of the sky, one would find huge numbers of galaxies. The HST did just such an experiment to produce this deep field image. Almost everything you see in this image is a separate galaxy.
Measuring Hubble's constant requires accurate distances to increasingly remote galaxies. One of the best distance measures is the Cepheid variable star. The HST has now been able to detect Cepheid variable stars in the galaxy M100 in the Virgo galaxy cluster. Several cepheids have been found such as this one. This new data gives us a distance to M100 of 17 Mpc and is consistent with a rather large Hubble constant of about 80 km/sec/Mpc.
Stars are an important constituent of the universe. Stars produce all the elements in the periodic table above Helium, massive stars explode in supernovae, small-massed stars may make up much of the hidden ``dark matter'' in the universe, and the age of the oldest stars is a lower limit to the age of the universe itself. Stars are born in dense molecular clouds. Here is a recent HST image of an Evaporating Gaseous Globule where stars are forming in great pillars of molecular hydrogen.
Stars come in many masses, but one of the most elusive types of stars is the low mass brown dwarf. Now astronomers have found clear evidence for a brown dwarf . The star, called Gliese 229B, is a companion to the cool red star Gliese 229. The brown dwarf is estimated to be 20 to 50 times the mass of Jupiter. Data from the HST indicates that the dwarf is no hotter than 1000 degrees K, and is near the theoretical limit where a star has enough mass to sustain nuclear fusion.
Active Galaxies are galaxies that show energetic activity in their cores. The best model for the "central engine" of active galaxies is a supermassive black hole in the core of the galaxy. Around this hole there is a huge disk of gas, slowling spiraling into the hole and releasing energy. The HST has looked deep into the heart of some nearby active galaxies. These galaxies have jets shooting out from their cores at relativistic energies and speeds. One image shows the giant elliptical galaxy, M87 , and the other shows the active galaxy NGC4261.
To learn more about the life of Galileo go to the Galileo Project Homepage. A research group at the University of Illinois has been doing supercomputer simulations of cosmological models. You can check out their current research and associated links, as well as images from a recent cold plus hot dark matter model. Another research group at the University of Washington has put together a picture gallery of cosmological data and simulations.
Researchers using the Lick Observatory in California have discovered planets around normal stars. These jupiter-sized planets were discovered indirectly by measurements of doppler shifts in the stars around which they orbit.
Interested in learning more about special and general relativity? The numerical relativity group at the National Center for Supercomputing Applications has some nice relativity pages. Go here for an index . A couple of specific examples include a page on Einstein and a page on black holes. There are a lot of interesting and informative links from there.
The LIGO project is an attempt to build a giant Michelson-Morley type interferometer to detect gravitational radiation. Two interferometers will be built, and each one will have perpendicular light-carrying vacuum pipes 5 kilometers long. Here is a gif image of the artist's conception of a LIGO interferometer. You may also wish to visit the LIGO home page.
