F L O R I
D A S T A T E
U N I V E R S I T
Final Exam or Test #4
What is listed here is not expected to be an exhaustive summary, but simply lists many of the high points; You should also use review questions and problems, self tests, and other materials at the ends of each chapter in the text, as well as any assigned homework problems, to assist you in your study.
Anything discussed in the textbook or class lectures is valid material to be included in the tests.
Each test will be multiple choice, consisting of ~25-30 problems, of which ~6-8 will be numerical. Useful information such as equations and numerical constants will be given to you on the test sheets; (The final exam will have 60 problems, of which ~12-16 will be numerical.)
You may use a standard scientific or business calculator during the test (make sure it has new batteries), and must bring both a #2 pencil and your university ID with you to the test.
Practice tests (old tests of from previous semsters of Dr. Lind's AST sections, that deal with the same material, and given in the same style as the tests you will take this term, with their accompanying keys), are handed out only to students that come to the test review sessions.
The summary outlines of the lectures (but not the practice tests) will be posted on-line at this site a few days to a week before each test to use as study materials.
When preparing for the Final Exam, you may use all of your old tests as study aids, (both the practice tests, and your own tests taken this term). Keys for the tests this term will be posted at this site a few days before that final exam to help you use them in your review.
The Origin and
|Galaxies and Beyond:
Our Galaxy, Other Galaxies, the Large Scale Structure
of the Universe, and the Big Bang
-- the ancients had for millenia seen our galaxy as a continuous band of glowing phosphorescence sweeping across the nighttime heavens, but didn't regognize it for what it was.
-- the Greeks called the glowing band galaxies kuklos or "milky circle".
-- the Romans gave it the name via lactea or "milky way".
-- it wasn't until Galileo turned one of the first telescopes at this milky band of light that it became apparent that the light was coming from the combines glow of billions of sitant stars.
-- disk (lots of gas, dust, and many hot young blue stars, Population 1 stars) and central bulge (little dust, old dim Population 2 stars) components.
-- halo of dark matter - the rotation rate of this galaxy (and other galaxies) is too fast unless there is a lot more mass in the outer part of the galaxy than can be accounted for in the visible stars. --> Dark Matter.
-- globular clusters (few hundred thousand stars each) - are in random elliptical orbits around the center of the galaxy out of the plane of the disk. -- because they orbit the center of the galaxy, their distribution in space should point to where and roughly how far away the center of the galaxy is (used by Harlow Shapley to show galactic center is a bout 27,000 ? 30,000 light years away in the direction toward to constellation Sagittarius).
-- much of the galaxy is, in fact, not visible from the Earth at optical wavelengths because the gas and dust are dense enough to block most light transmission.
-- Population I - like the sun; found in the spiral arms of the galaxy, contain ~2% "metals" (elements heavier than He); are actually a second generation of stars, created from matter generated in a previous cycle of star formation.
-- Population II - no metals; only H and He; in nuclear bulge and halo; oldest stars.
-- from the gravitational collapse of a rotating cloud of gas and dust (sound familiar?).
-- the first regions that get dense enough for star formation become the nuclear bulge and globular clusters (oldest stars - Population II);
-- remaining gas flattens into spinning disk (provides fuel for continuing star formation - Population I).
-- element building cycle: matter originally only hydrogen and helium (from Big Bang); elements with masses up to iron are created in main sequence and Red Giant stars; heavier elements created only in supernovae.
-- mapping of the spiral sructure measured by measuring the Doppler shifts and direction of 21-cm radio emission from cool hydrogen gas.
-- positions of Cepheid variable stars, molecular gas clouds, open clusters, and hot young O and B stars also mark the positions of the spiral arms
-- theories of spiral arm formation: density wave theory (Be able to explain, at least briefly.)
-- self-sustaining star formation from rotation of the galaxy (shock waves), and from supernovae, etc.
-- in the constellation Sagittarius, obscurred by intervening dust and gas.
-- very bright in IR, Radio, x-ray, and gamma rays --> very powerful emitter. (called Sgr A*)
-- also in a region of very high star density (and they are moving very fast in there orbital motion -- indicating a very massive object nearby.
-- exhibits characteristics of a rapidly rotation accretion disk and jets --> supermassive (>3 million solar mass) BLAC K HOLE.
-- Spiral Galaxies:
* Population I stars in spiral arms, Population II stars in bulge and halo.
* ~33% of all galaxies; among large galaxies, most (75-80%) are spiral and lenticular galaxies.
* spiral galaxies are indexed by how tightly would their arms are and how larger their nuclear bulge is.
-- SO galaxies (also called lenticular galaxies) don't have as much dust or gas as other spirals, and have a large nuclear bulge and smaller disk with no obvious spiral structure.
M104 'Sombrero galaxy'
-- Sa, Sb, Sc,
and Sd, (all regular spiral galaxies) in sequence
have more and more gas and dust, have smaller and smaller nuclear bulge,
have more and more loosely wound spiral arms forming their disks.
-- SBa, SBb, SBc,
and SBd, (barred spiral galaxies) follow the same
sequence in gas and dust, nuclear bulge size, and arm winding as regular
spirals, but have elongated barlike central bulges.
* Contain almost no dust or cool gas; thus essentially no new star-birth is going on in these galaxies.
* No hot, bright, young O & B stars ??> appear reddish in color.
* The largest of all galaxies are giant ellipticals, found near the centers of rich clusters (e.g. M87).
* Ellipticals represent only 15% of all large galaxies found outside rich clusters but about half those found in rich clusters. Ellipticals are very common among small galaxies.
* most ellipticals are a single generation of older Pop. II stars.
M87, near center of Virgo Cluster
* white and often quite dusty, like the arms of spiral galaxies.
* these often include large quantities of both old and new stars.
Large Magellanic Cloud, a small companion galaxy to the Milky Way.
(and how to find them)
-- galactic distances:
* Most galactic distance measurements use "standard candles" -- bright objects within the galaxies for which the actual brightness (luminosity, or it's equivalent on the magnitude scale called 'absulute visual magnitude' MV) is known or measurable by some indirect technique, and for which the apparent brightness (or it's equivalent, the apparent magnitude, m) can also be measured. Because of the inverse square law of light, a relation between these two magnitude scales exists, that allows us to calculate object's distance:
distance modulus equation:
-- where m is the apparent visual magnitude of the object (measured through a telescope),
-- Mv is its absolute visual magnitude (already known, or indirectly obtained, as with the luminosity of Cepheid variables from their period of oscillation)
-- and d is the distance to the object (calculated).
-- average brightness of the brightest stars in galaxy
-- globular cluster brightness
-- HII region (emission nebula) average size and brightness
-- supernovae brightness
-- average brightness of entire galaxy
-- Hubble Law
* In the 1920's Edwin Hubble found that all galaxies are moving away from each other at a rate that is proportional to their distance from us.
* both of these indicate that only about 10% of the mass of galaxies are in their luminous stars --> the missing mass must be in some type of unobserved DARK MATTER, which appears to account for about 90% of the mass of the universe!!
-- rich galactic clusters:
* very dense; contain many elliptical galaxies; often have a giant elliptical galaxy at its core (galactic cannibalism).
* the Local Group (w/ Milky Way, Andromeda galaxy, and about 30 others) is a good example of a poor cluster.
-- Colliding galaxies:
* undergo collisions, interact tidally, form long extended stellar tails, and cause galactic cannibalism;
* collisions are the probable origin of largest elliptical galaxies.
Antennae galaxies (NGC 4038/4039) showing HST image of the central cores of the two galaxies
This page last updated on April
1, 2004 by David M. Lind
© 2004 Department of Physics, Florida State University. All rights reserved.