Harvard University Department of Astronomy

The Cosmological Constant Cosmic Inventory Basic Idea: Contents: where and what, scales Motivation: The measured effects of the cosmological constant are primarily in the field of cosmology, the study of the universe as a physical system. In order to provide a context for the various subsequent sections, this section will describe many of the objects in the universe and relative sizes, and the next section will very briefly summarize the current paradigm for the history of the universe. Note that cosmological inventory is still underway at the frontiers of cosmological research. Contents: Interest here is in subset of astronomical objects, many of which are quite large. Cosmic Voyage and powers of 10: relative sizes Some Objects and Scales nearby objects earth sun solar system next nearest star milky way cosmological objects galaxies cluster super cluster note: mapping out the universe locally and beyond is a major current research project What are they made of? familiar matter: baryons, photons, neutrinos dark matter evidence Types: hot, cold Exotic particle candidates--particle physics has many possible suggestions but no particle physics detections either direct or indirect yet. Many searches are underway. Difficult-not clear where to look given their weak interactions Current issues: self interactions, how light traces mass Combined matter content picture Some other objects used in later sections: globular clusters black holes/supermassive black holes/quasars supernovae Cepheids LMC lyman alpha forests Wavelengths/observations: radiation is all around us! photons: spectrum finite speed of light: look at large distances, seeing back in time examples--how far corresponds to how long ago in terms of z, pc distance to farthest visible objects search for earliest objects (farthest) underway by many groups neutrinos cosmic rays gravity waves Some references. Home Syllabus References Lecture References Useful Links Contact Info Back to Harvard University Department of Astronomy Academics. Back to Harvard University Department of Astronomy Courses.