Virtual Laboratories for Introductory Astronomy

by Michael Guidry, University of Tennessee and Kevin M. Lee, University of Nebraska

The Brooks/Cole Virtual Astronomy Laboratories consist of 20 virtual online astronomy laboratories (VLabs) representing a sampling of interactive exercises that illustrate some of the most important topics in introductory astronomy. The exercises are meant to be representative, not exhaustive, since introductory astronomy is too broad to be covered in only 20 laboratories. Material is approximately evenly divided between that commonly found in the Solar System part of an introductory course and that commonly associated with the stars, galaxies, and cosmology part of such a course. The VLabs are packaged with the Seeds, Pasachoff & Filippenko, and the Fraknoi, Morrison, & Wolff texts and also may be purchased as a standalone product. Please visit the Brooks/Cole Astronomy site for more information or contact your local Brooks/Cole representative.

Intended Use

This material was designed to serve two general functions: on the one hand it represents a set of virtual laboratories that can be used as part or all of an introductory astronomy laboratory sequence, either within a normal laboratory environment or in a distance learning environment. On the other hand, it is meant to serve as tutorial material supplemental to standard textbooks. While this is an efficient use of the material, it presents some problems in organization since (as a rule of thumb) supplemental tutorial material is more concept oriented while astronomy laboratory material typically requires more hands-on problem-solving involving at least some basic mathematical manipulations.

As a result, one will find material of varying levels of difficulty in these laboratories. Some sections are highly conceptual in nature, emphasizing more qualitative answers to questions that students may deduce without working through involved tasks. Other sections, even within the same virtual laboratory, may require students to carry out guided but non-trivial analysis in order to answer questions. In this manual, we shall provide some information about choosing portions of laboratories for particular environments by classifying the sections of the Vlabs according to three levels of difficulty, and by providing sample tracks through the material that would be appropriate for several different levels of course usage and student engagement.

Table of Contents

1. Units, Measure, and Unit Conversion
2. Properties of Light and Its Interaction with Matter
3. The Doppler Effect
4. Solar Wind and Cosmic Rays
5. Planetary Geology
6. Tides and Tidal Forces
7. Planetary Atmospheres and Their Retention
8. Extrasolar Planets
9. Asteroids and Kuiper Belt Objects
10. Helioseismology
11. The Spectral Sequence and the HR Diagram
12. Binary Stars
13. Stellar Explosions, Novae, and Supernovae
14. Neutron Stars and Pulsars
15. General Relativity and Black Holes
16. Astronomical Distance Scales
17. Evidence for Dark Matter
18. Active Galactic Nuclei
19. The Hubble Law
20. Fate of the Universe

The User's Guide contains a complete description and screen shots of each lab.

Simulation Example: Asteroids and Kuiper Belt Objects -- Resonance

One of the intriguing features of the asteroid belt is the lack of asteroids with certain semimajor axis values. Some of these lacunae -- known as the Kirkwood Gaps -- are clearly visible in a histogram showing the distribution of semimajor axis values of asteroids (click to open). These gaps come about from resonant perturbations by Jupiter that quickly pull any asteroid that may have such a semimajor axis into a new orbit.

The Kirkwood Gaps have shown that resonance can influence the orbits of asteroids, but what about other small solar system bodies? In 1992 the first Kuiper Belt Object, or KBO, was discovered beyond the orbit of Neptune. Hundreds of these cold, icy objects have been discovered since then. Are resonance patterns apparent in the Kuiper Belt?

A plot of the KBO distribution reveals the answer (click to open). In the graph we see the eccentricity versus semimajor axis plotted for over 500 KBOs. A striking feature of this graph is the column of KBOs at 39.4 AU. These are KBOs that are in 2:3 resonance with Neptune -- that is, they complete two orbits of the Sun for every three Neptune orbits. These are also called plutinos since Pluto is a member of this group.

Although resonance is clearly affecting these KBOs, it must be different kind of resonance than that between Jupiter and the main-belt asteroids since these KBOs are selectively maintained in their orbits instead of being scattered. What is going on? In the VLab we encourage students to discover the answer by noticing how the closest approach distance to Neptune depends on the KBO's orbital parameters. KBOs that get too close to Neptune are at risk of being scattered over time. A KBO orbit simulator allows students to create asteroids with different eccentricities and semimajor axes and follow a chart showing the KBO-Neptune distance (click to open). Create an asteroid with a semimajor axis of 39.39 AU and eccentricity of 0.35 and you will see that the KBO never gets closer than about 23 AU to Neptune, even though its orbital path crosses Neptune's.

The use of computer simulations to allow students to discover relationships like KBO resonances is a central feature of the VLabs.

Interactive DataSet Example: Neutron Stars and Pulsars -- Distribution of Periods

Pulsars are rapidly rotating neutron stars that emit very regular, short bursts of energy (usually in radio waves, but some pulsars also flash in x-rays and visible light). Careful observations of pulsars over time show that they slow down over time, that is, their periods increase. The rate the period changes is referred to as the spindown rate (labelled [p with dot], or "p-dot"). VLab students are encourged to explore the p and pdot values for pulsars in an interactive p-pdot diagram (click to open).

Allowing students to explore datasets of real astronomy data is another mainstay of the VLabs.