Phys 181 Astronomy

Readings: ASTRONOMY TODAY Ch 23.1, 23.2 Ch 24.1, 24.2, 24.5 Ch 26 ReadingsReadings

Quotes There was no "before" the beginning of our universe, because once upon a time there was no time. * John D. BarrowJohn D. Barrow I don't pretend to understand the Universe--it's a great deal bigger than I am. * Thomas CarlyleThomas Carlyle A universe that came from nothing in the big bang will disappear into nothing at the big crunch. Its glorious few zillion years of existence not even a memory. * Paul DaviesPaul Davies Anyone informed that the universe is expanding and contracting in pulsations of eighty billion years has a right to ask, "What's in it for me?" * Peter De Vries Nothing puzzles me more than the time and space; and yet nothing troubles me less. * Charles LambPeter De VriesCharles Lamb

Exam ReviewExam Review EXAM REVIEW The final exam will consist of a choice of TWO (2) essays, selected by the student, from a list of FIVE (5) essay topics chosen by the professor. Essays should be a minimum of FOUR (4) bluebook pages in length. ESSAY TOPICS Key discoveries in the history of Astronomy. The role of Kepler’s laws in understanding the motions of the planets. A comparison of the evolution of high and low mass stars. A description of General Relativistic effects and their predictions regarding Black Holes.

Essays will be scored on the following criterion: Coherence Accuracy of information Presence of four supporting arguments or evidence from the lecture or readings. Presence of one referenced supporting argument or evidence from another source. Conventional development: Thesis – Support – Conclusion Reasonable grammar

Milky Way Galaxy

The Milky Way Galaxy: Vital Statistics Diameter - 100,000 light years Thickness (Nucleus) - 20,000 light years Thickness (Disc) - 2,000 light years Number of Stars - 200,000,000,000 Age - 15,000,000,000 years

The Halo

The Disk

The Core

Elliptical Galaxies 1/3 of all galaxies Giant Ellipticals are the size of our galaxy but are rare Dwarf Ellipticals are more common (6000 light yrs across) Riesen-E

Spiral Galaxies Largest fraction of galaxies Andromeda

Barred Spiral Galaxy NGC-1365

Irregulars Large Magellanic Cloud

Galaxies form groups or Clusters Coma Cluster

Olber’s Paradox

The universe is expanding!

Hubbles Law