Phys 181Astronomy

Readings: ASTRONOMY TODAY

Ch 23.1, 23.2 Ch 24.1, 24.2, 24.5Ch 26Readings

QuotesThere was no "before" the beginning of our universe, because once upon a time there was no time. * John D. Barrow I don't pretend to understand the Universe--it's a great deal bigger than I am. * Thomas 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 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 Lamb

Exam ReviewEXAM REVIEWThe 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

Chronologically discuss key discoveries in the history of Astronomy.

Describe Keplers three laws with particular emphasis on their role in understanding the motions of the planets around the sun.

A comparison of the evolution and fate of high and low mass stars.

A description of Einsteins Principle of Equivalence, its effects, and predictions regarding Black Holes.

Give a brief summary of each of the popular possibilities for the fate of our universe, and suggest the evidence that may support each.

History of Astronomy:

Keplers lawsKeplers LawsEach planet moves in an ellipse, with the sun at one focus.

The line between the sun and the planet sweeps out equal areas in equal times.

The ratio of the cube of the average radius of a planets orbit to the square of its orbital period of revolution is the same for each planet. (Harmonic Law)

High and Low mass stars:

Principle of Equivalence:

Essays will be scored on the following criterion:

CoherenceAccuracy of informationPresence 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 ConclusionReasonable grammar

Milky Way Galaxy

The Milky Way Galaxy: Vital Statistics

Diameter - 100,000 light years Thickness (Nucleus) - 20,000 light yearsThickness (Disc) - 2,000 light years Number of Stars - 400,000,000,000 Age - 15,000,000,000 years

The Halo

The Disk

The Core

Elliptical Galaxies1/3 of all galaxiesGiant Ellipticals are the size of our galaxy but are rareDwarf Ellipticals are more common (6000 light yrs across)

Riesen-E

Spiral GalaxiesLargest fraction of galaxies

Andromeda

Barred Spiral GalaxyNGC-1365

IrregularsLarge Magellanic Cloud

Galaxies form groups or ClustersComa Cluster

How do we measure our universe?

Radar Ranging:We measure distances in our solar system by bouncing radio waves off planets, for example.

Geometry helps us to interpret the results.Within one light-hour.

Parallax:The distances to objects are determined by observing apparent shifts with respect to background objects.100 light-years

Main-Sequence Fitting:We know the distance to the Hades Cluster in our own galaxy.

Comparing the intensities of main sequence stars in Hades to the main-sequence stars of other clusters in our galaxy allows us to infer their distances.100,000 light-years

Cepheid Variables:There is a period-luminosity relation for Cepheids.

Studying this relationship for Cepheids nearby allows us to determine the luminosity of Cepheids in other, nearby galaxies.10,000,000 light-years

Distance Standards:Luminosities of white dwarfs in nearby galaxies are determined.

There is a rotational period-luminosity relation for galaxies allowing us to determine the luminosities of more distant galaxies. (Tully-Fisher Relation)10,000,000,000 light-years

Hubbles law: v=H*d>10 Billion light-years

Olbers Paradox

The universe is expanding!

THE END?