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PCS 181 Lecture Notes - Milky Way, The Demon-Haunted World, Dark Matter Halo

Course Code
PCS 181
Margaret Buckby

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Currently these notes cover: a brief overview of astronomy's place in the scientific
endeavor, the philosophy of science and the scientific method, astronomy that can be
done without a telescope, a history of astronomy and science, Newton's law of gravity
and applications to orbits, Einstein's Relativity theories, electromagnetic radiation,
telescopes, all the objects of the solar system, solar system formation, determining
properties of the stars, the Sun, fusion reactions, stellar structure, stellar evolution, the
interstellar medium, the structure of the Milky Way galaxy, extra-galactic astronomy
including active galaxies and quasars, cosmology, and extra-terrestrial life. This site
also has pages giving angular momentum examples, a quick mathematics review,
improving study skills, astronomy tables, and astronomy terms.
All of the line drawings were done with Create on my old NeXT machine or with
Freehand on a wintel laptop and Macintosh at home. The line art images on the screen
are GIF and PNG images. If you have comments about these notes, please email me.
Some significant updates since the major 2010 revision are listed below in the
chapter descriptions. There are other tweaks not listed on this homepage.
Contents (chapters + descriptions):
1. Astronomy as a Science and a Sense of Scale. I introduce astronomy's place in
science, and give a sense of the size and time scales involved. Section on
astrology expanded.
A separate section about the Science-Religion interface and interaction is
available on this site. It is not part of the regular textbook. I take a middle road
between the fundamentalists on both sides of the "debate"/dialogue.
2. Method for Finding Scientific Truth. Borrowing from Pine's book ``Science
and the Human Prospect'' I discuss the scientific method, correlations, problem
of induction, positivism, levels of testimony, empiricism, models
correspondence with reality.
Pseudoscience vs. science article. Borrowing from Carl Sagan's "The Demon-
Haunted World", I take up the subject of UFOs as alien spacecraft. This article
is not part of the regular textbook.
3. Astronomy Without a Telescope. I discuss the celestial sphere, motions of the
Sun (solar and sidereal days, time zones, equation of time, and seasons),
motions of the Moon (phases and eclipses), and planetary motions. May 20,
2012 annular eclipse.

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

4. History of Astronomy. I focus on the rise of modern science in Europe, from
the ancient Greeks to Kepler.
5. Newton's Law of Gravity. Newton's laws of motion and his law of gravity are
discussed. Applications of those laws (esp. gravity) are covered (e.g.,
measuring the masses of planets and stars, orbital motion, interplanetary trips,
tides, etc.).
6. Einstein's Relativity. I discuss Einstein's Special Relativity and General
Relativity theories. The concepts of spacetime and gravity as a warping of
spacetime are introduced along with observational proofs of his
theories. Section on observational proofs was updated with information
about LIGO
7. Electromagnetic Radiation (Light). General properties of light, definition of
frequency, spectrum, temperature. Light production: Continuous (thermal)
spectra, emission lines, absorption lines and the Bohr model for the atom.
Doppler Effect and why spectral lines must be used to measure the doppler
8. Telescopes. Covers refractors, reflectors, radio telescopes, light-gathering
power, resolving power, interferometers, magnification, and atmospheric
distortion such as seeing, reddening, and extinction. Section on radio
telescopes was updated with information from my visit to NRAO at Green
9. Planetary Science. This chapter is an introduction to planetary science. I
discuss the techniques astronomers use to find out about the planets, their
atmospheres (what determines if an atmosphere sticks around; behavior of
gases; what determines the surface temperature; atmosphere layers; the
transport of energy; effects of clouds, mountains, and oceans; weather vs.
climate and climate change agents with feedbacks; and appearance), their
magnetic fields (the magnetic dynamo theory), and their interiors including the
geological forces at work reshaping their surfaces. In a separate section I focus
on a comparison between the atmospheres of Earth, Venus, and Mars and why
they are now so radically different from each other (greenhouse effect, carbon
cycle, runaway refrigerator, runaway greenhouse, etc.) Mars discussion now
includes proofs for liquid water in past and sub-surface water ice. The Earth
discussion now includes the role of plate tectonics in the carbon cycle, evidence
for human contribution to the atmospheric carbon dioxide and to the observed
global temperature rise. There are links to two flowcharts: a Earth-Venus-Mars
comparison and a flowchart of the calculations involved in determining if an
atmosphere sticks around for billions of years. I end the chapter with a
discussion of the major moons in the solar system and ring systems. Updates
include: how paleoclimate is measured, Snowball Earth evidence, Mars
discoveries (including notes from January 2011 "Follow the Water"

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

forum), meteorites from Mars, Titan and Enceladus discoveries, and
clarifications in discussion of human-caused climate change.
Beautiful Planet photo album of nature photography has imagery of
mountains, lakes, streams, waterfalls, large trees, flowers, aurorae, other
landscape images and some images of insects and frogs. Most images are from
the western United States but some are also from eastern Australia and the
aurorae are from Fairbanks, Alaska. National park photo sets include: Crater
Lake, Bryce Canyon, Grand Canyon, Zion, Grand Teton, Yellowstone, Devils
Tower, and Glacier. The rest of the album are from various beautiful places in
the western United States and eastern Australia.
Answers to Global Warming Skeptics is a separate section about the climate
change debate going on among the general public. It is not part of the regular
textbook. The section has been updated, including the latest "going down
the up escalator" results.
10. Solar System Fluff. The basics of meteorites, asteroids, and comets are
introduced and how they can tell us the ``when'' and the ``how'' of the
formation of the solar system. At the end is an exploration of the other
planetary systems. Updates on Comet Hartley discoveries, exoplanet
discoveries including those from the Kepler mission and free floater
exoplanets, potentially hazardous asteroids (plus new section on deflecting
and using asteroids), meteorites from Mars, and early history of the solar
system. Commentary on planet definition added and also meteor shower
table now has meteor speeds.
11. Determining Star Properties. Notes for the properties of stars and how we
determine them. Things like distances to stars, their masses, radii, composition
and speeds. Also HR diagram, spectral types, and spectroscopic parallax. The
dangers of selection effects and biased samples are also discussed with the
application of finding what a typical star is like.
12. The Sun and Stellar Structure. This chapter covers: The Sun, interiors of stars,
and nuclear fusion, neutrinos, the solar neutrino problem, and helioseismology.
The concept of hydrostatic equilibrium is used to explain the mass-luminosity
relation and the reason for the mass cut-off at the high and low ends. Brown
dwarf discussion expanded. Asteroseismology section added.
13. Lives and Deaths of Stars. This chapter covers: stellar evolution (all nine
stages) and stellar remnants (white dwarfs, neutron stars, black holes).
14. The Interstellar Medium and the Milky Way. This chapter covers: the dust and
gas between the stars and how we use the 21-cm line radiation to map the
Galaxy. Also, the structure of the Milky Way Galaxy, our place in it, and how
we determine these things. The rotation curve and the existence of the dark
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