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As a testament to the value of this material, numerous copies of
this material (in various stages of revision) are found all over the
``strobel astronomy'' in any of the internet search engines will bring
up a lengthy list of some of the copies out there. If you find
an old copy, please let the website manager know of the official Astronomy
Notes website at www.astronomynotes.com.
These documents were created by Nick Strobel for the introductory astronomy
courses he teaches. They are copyrighted by
Nick Strobel. This website is offered to the net as a resource in astronomy
education. See my copyright notice for fair
use practices. You can now purchase a hardcopy version of this website!
Select the Purchase Book link for ordering
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
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 images. If you have comments about these notes, please email me.
Search the site
- 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.
A new separate section about the teaching of Intelligent
Design in our public schools is now available on this site.
It is not part of the regular textbook.
- 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
- 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.
- History of Astronomy.
I focus on the rise of modern science in Europe, from the ancient Greeks to
- 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.).
- 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.
- 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 shifts.
- Telescopes. Covers refractors,
reflectors, radio telescopes, light-gathering power, resolving power,
interferometers, magnification, and atmospheric distortion such as seeing,
reddening, and extinction.
- 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, the transport of
energy, and appearance), their magnetic fields (the magnetic dynamo
theory), and their interiors. 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, etc.) There are links to
three graphical descriptions of the concepts covered: the Earth-Venus-Mars comparison
(a flowchart), the greenhouse effect and the UV dissociation of water, 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.
Two new additions: "Earth beautiful" scenery
photography section and a zoom-in
movie to the Mars Exploration Rover locations. Yosemite pictures were
added to the "Earth beautiful" albums. Also, the Titan (Saturn's large
moon) section has been updated with Cassini-Huygens results.
- 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
other planetary systems.
The other planetary systems has been greatly expanded and updated!
- 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
Two new illustrations and accompanying text added to illustrate how luminosity,
temperature, and size depend on each other. Also, a couple of points in the
star masses section have been clarified (see the "caution" notes).
- 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.
- Lives and Deaths of Stars.
This chapter covers: stellar evolution (all nine stages) and stellar remnants
(white dwarfs, neutron stars, black holes).
- 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 matter halo, stellar populations, and the galactic center are also
- Other Galaxies and Active Galaxies.
This chapter covers: the
characteristics of other normal galaxies, active galaxies, and finding distances to
(this includes the distance-scale ladder). Also, large-scale structure is covered
(galaxy clusters and collisions and superclusters).
This chapter covers cosmology: the study of the nature, origin, and
evolution of the universe as a whole. The distance-scale topic is dealt with
the Steps to the Hubble Constant document. I discuss
Olbers' Paradox, the cosmic microwave background radiation, the fate of the
universe (open or closed), dark matter, inflation, and the cosmological
This chapter has been greatly updated!
- Life Beyond the Earth.
This chapter covers: lifezones, types of stars to focus on in
the search for suitable planets, basic definitions of life, the kind of
planet where we think life would likely arise, and finally the frequencies we
use in the Search for Extra-Terrestrial Intelligence (S.E.T.I.).
- Angular Momentum in Astronomy.
I define angular momentum and
give several examples of angular momentum in astronomy: Kepler's second law
of orbital motion, Earth-Moon system, rapidly spinning neutron stars, accretion
disk in a binary system, and a collapsing galactic cloud.
- Quick Mathematics Review. Here's a quick run
through of some basic mathematics: working with fractions and percentages,
exponents, roots, powers of ten, working with really BIG or really small numbers---scientific
notation and the metric system. I assume that the reader has had this stuff
before, so the quick run through will be sufficient to jog the dormant memory.
Astronomy constants, physical constants, planets (orbital properties,
physical characteristics, atmospheres), 100 nearest stars, and 100
brightest stars as seen from the Earth.
Definitions of astronomy terms used in this website.
From the Student Guide:
Astronomy beyond this website:
- Study Skills: Great Expectations, Textbook
reading'', homework and exams.
College is not high school---greater expectations of the student! Also, some
take exams with better results. Although the homework and exam tips are
addressed to my own students, most of these tips will also apply to students
This page last updated:
April 21, 2006
(note individual pages in this website may have been updated after this date)
Is this page a copy of Strobel's
Author of original content: