Astronomy 110 Laboratory: Course Outline

Fall 2007 Astronomy 110L Thurs. 6:00 - 9:00 pm

FORMAT

One evening meeting per week, involving a combination of short lecture, laboratory work, use of astronomical computer software, and field trips for astronomical observations. There will be one daytime meeting to view the Sun, and one or more nighttime field trips to a dark site to view the Milky Way and faint objects. Enrollment will be limited to 24 students per section.

Flexibility is necessary in conducting this course. At any given time only some planets and other objects are visible. Moreover, observing may be impossible during bad weather; when it's cloudy, laboratory exercises or work with astronomical computer software will be substituted for astronomical viewing. From time to time, additional viewing sessions may be scheduled to take advantage of unique astronomical events such as eclipses, meteor showers, occultations, etc.

Warning: this section is still in development, and some parts may be added or change in the future. This warning will be deleted after all additions and changes have been introduced.

OVERVIEW OF THE PROGRAM

-1. Organization. Release form. Transportation to and from Kapiolani Park. Procedures, general information, grading system. Books required and recommended. An astronomical reflecting telescope: description, assembly, first use. Questionnaires. The five-minute astronomy talk. Burning questions. Visit to the computer laboratory and first contact with the computers.

0. Starting point: primitive man and primitive thinking. Hypothetical ideas about the first rational thinkers. Starting assumptions: we need to postulate the existence of (1) an objective reality, accessible to all observers, and of (2) natural laws without exceptions. Reason alone is not enough: the case of Aristotle. Experimental control: the example of Galileo. The modern scientific method and the ideas of Karl Popper. Distinguishing science from pseudo-science.

Practical activities: observation and orientation. The celestial sphere, cardinal points, other basic features. Coordinate systems. Measuring time. Time zones. Universal time. Julian dates.

1. First step: sphericity and rotation of the Earth. Experimental evidence: Eratosthenes, Foucault's pendulum. Day and night: the Earth as a dark body. The Sun is hot, but the Earth is not. The Moon and its importance as a second example of dark body. Lunar phases and lunar sphericity. Testing a model: explanation of lunar phases as a function of position relative to the Sun.

Practical activities: getting familiar with maps of the sky. The brightest stars in the sky, the most easily recognizable constellations. Mapping the positions of the Moon for different phases. Angles and their units: degrees and radians. Measuring angular distances.

2. Second step: physical size, angular size, and their relation with distance. The size of the Earth. Parallax and the distance to the Moon. Size of the Moon. Are the Sun and Moon at the same distance from us? The argument by Aristarchus as a test to be decided by observation. Lunar eclipses and verification of sizes and distances.

Practical activities: using the astronomical ephemeris to test intervals betweeen lunar phases. Star brightnesses and the magnitude system. Variable stars: locating Delta Cephei. Graphs and functions: how to plot a variable quantity as a function of another. Plots as a function of time: periods and phases.

3. Third step: a first idea of the size of the Sun. What moves around what? The planets and their complicated apparent motions. Demonstration of the comparative simplicity of the heliocentric system. Prediction: phases of Venus. Galileo and his telescopic discoveries. Confirmation of the heliocentric system. Kepler's laws. Determination of distances within the inner Solar system by radar. Distances to the Sun and to all planets in the solar system using Kepler's third law. Sizes of the Sun and planets.

Practical activities: mapping the motions of planets across the constellations. The apparent size of the Moon, and Kepler's laws. Visual or binocular observations of Delta Cephei. Laboratory activity: study of a simple telescope.

4. Fourth step: Gravitation. From "all things fall down" to the concept of central attraction from a spherical body. Newton's contribution: the apple and the Moon obey the same law. Newton's universal gravitation law. Determination of G, the constant of gravitation, and of the mass of the Earth. Confirmation using Kepler's third law. Masses of the planets and of the Sun. Regularities in the Solar system and their probable origin.

Practical activities: telescopic observations of planets and asteroids from Kapiolani Park.

5. Fifth step: stars as faraway suns. An argument based on observations of occultations of stars by the Moon. Huygens's experiment and his first distance estimate. Distance measurements: stellar parallaxes. Color-mag diagrams. Apparent and intrinsic brightness. Stellar luminosities. Main sequence. The Pleiades: a typical star cluster. Cluster diagrams. Cluster distances. Cepheid variable stars, period-luminosity relation and its calibration. Globular clusters and their distribution. The Milky Way as a stellar system (Galaxy) and the location of the Sun.

Laboratory activity: parallax in the lab. Extra activity: observations of the Sun, to be performed near noontime at a date to be agreed upon.

6. Sixth step: galaxies. Cepheids in Andromeda's galaxy. A universe of galaxies. Wave model of light. Rainbows: the spectrum of our Sun. Spectroscopes and spectrographs. Spectra of stars, nebulae and galaxies. The Doppler effect and its uses. Binary star systems and stellar mass determinations. Redshifts of distant galaxies. Hubble and the expansion of the universe. Looking back in time. The big-bang model and the steady-state universe.

Laboratory activity: spectra in the lab.

7. Structure of matter. Natural forces. Quantum model of light: photons. Interactions between matter and radiation. Interpretation of stellar spectra. Chemical composition of stars. Stellar populations, metallicity. The age of Earth and how to keep the Sun shining for so long. The source of the Sun's energy. Star formation and stellar evolution. Supernovae and black holes. The origin of chemical elements. Chemical history of our Galaxy.

Practical activities: deep sky telescopic observations from Sandy Beach.

8. How old is the universe? Olbers's paradox: why is it dark at night? The model of a homogeneous, infinite and eternal universe, and its refutation.

Practical activities: deep sky telescopic observations from Sandy Beach.

9. Big-bang model: predictions and observational verification. The microwave background radiation. A sketch of the history of the universe. Again the Doppler effect: dark matter and its role in the formation of galaxies. Supermassive blackholes in nuclei of galaxies. Quasars. Extragalactic supernovae and the acceleration of the universal expansion. Unsolved problems.

Practical activities: final telescopic observations from Kapiolani Park.

10. Back to Earth. The Apollo program and lunar rocks. The impact theory of lunar formation. Comparative planetology: Venus, Earth and Mars. The greenhouse effect. Meteorites, craters and dinosaurs. A comet collision with Jupiter. Search for asteroids that might impact our Earth. Other cosmic dangers. Long-term survival strategies.

No practical activities. The End.

MORE DETAILED DESCRIPTIONS OF PRACTICAL ACTIVITIES

The activities that can actually be undertaken change from semester to semester, depending on the visibility of astronomical objects. In Fall 2007 we will not be able to include all the exercises listed here (for example, we will not have a chance to see Venus or Saturn), but I have not deleted them because they may be again possible in the future, and because some students might be interested in some extra reading. Note that some sections have not been updated and remain as they were in 2005. My thanks to Josh Barnes, who provided most of the older material, and to Mike Nassir.

  1. The Sky
    1. Orientation: compass points, rising and setting of astronomical objects [outdoor].
    2. Constellations: recognizing landmarks in the sky [outdoor].
    3. Phases of the Moon: relation between position and phase of the Moon [outdoor].

  2. Telescopes
    1. A Simple Telescope: study formation of inverted images, predict and measure magnification [indoor].
    2. Using Astronomical Telescopes: finding objects, tracking, choice of magnification [outdoor].
    3. Advantages of Aperture: count stars visible after stopping down to different apertures; examine resolution of close binary stars [outdoor].

  3. Observations
    1. The size of our planet: watch a sunset at the beach and measure the Earth's radius [outdoor].
    2. Viewing Mars: in November 2005, Mars comes close to the Earth, providing an opportunity for detailed observations [outdoor].
    3. Viewing the Moon: small telescopes reveal an enormous amount of detail on the surface of the Moon [outdoor].
    4. A Lunar Occultation: watch the Moon cover a star, to place limits on the star's angular diameter [outdoor].
    5. Deep Sky Objects: study appearance of double stars, star clusters, nebulae, and galaxies [outdoor].
    6. Light Curves of Variable Stars: naked-eye observations of Delta Cephei can yield its period, and hence its luminosity [outdoor].
    7. Observing rainbows: you have to do this on your own, because we cannot predict where and when will a rainbow appear! [outdoor].
    8. Lunar eclipse: if you are sleepless on Sunday night (October 16), stay awake two hours into Monday 17 and you will see a partial lunar eclipse [outdoor].
    9. Viewing Venus: watch Venus getting bigger and bigger, and changing phases like the Moon [outdoor].

  4. Dynamics
    1. Motions of Venus and Mars: observations of these two planets reveal consequences of our own motion around the Sun [outdoor].
    2. Shape of the Moon's Orbit: the ~13% change in the Moon's apparent diameter from perigee to apogee provides a test of Kepler's first law [outdoor].
    3. Falling Bodies: recreate Galileo's key experiments and establish link to orbital motion [indoor].

  5. Distances
    1. Parallax in the Lab: use cross-staff to estimate distances by triangulation [indoor].
    2. Distance to the Moon: coordinated observation from two points yields estimate of lunar distance [outdoor].
    3. Inverse-Square Law: verify relationship between distance and apparent brightness [indoor].

  6. Spectra
    1. Spectra in the Lab: each element has a unique ``fingerprint'' of spectral lines [indoor].
    2. Solar Spectrum: observe absorption lines in Sun's spectrum [outdoor].
    3. Viewing Stellar Spectra: the spectra of stars reveal stellar temperatures and compositions [outdoor].

It is not possible to give a detailed week-by-week schedule for this course. Things are not likely to happen exactly as listed in the "overview of the program". We will have a range of activities prepared for each meeting; thus we can take advantage of clear weather, and work indoors when the weather is bad. Some topics can be completed in a week or two, but others entail observations spread over longer periods. In particular, repeated observations are necessary to follow the motion of planets and asteroids (for example Mars in 4.a), study the shape of the Moon's orbit (4.b), and measure the light curves of variable stars (3.f).


Roberto H. Méndez (mendez@ifa.hawaii.edu)

Last modified: August 20, 2007
http://www.ifa.hawaii.edu/~mendez/ASTRO110LAB07/aoutline.html