The Universe on a Desktop: Observational Astronomy Simulations in the Instructional Laboratory

Laurence A. Marschall, PASA, 17 (2), 129.

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Details of the Exercises

There are currently 9 CLEA exercises, covering a wide range of techniques and concepts from planetary astronomy to cosmology. The software runs under Windows, although one color Mac lab is available, and a number of rudimentary black and white Mac programs, lacking in many of the features of the Windows programs, are available as well. A brief description of each exercise follows:

1) The Revolution Of The Moons Of Jupiter Students observe the moons of Jupiter at fixed intervals for several weeks to verify Kepler's 3rd law and to measure the mass of Jupiter.

2) The Rotation Of Mercury Using Doppler Radar Students measure the equatorial velocity of Mercury using radar echoes from a simulated radio telescope.

3) The Flow Of Energy Out Of The Sun Students conduct experiments in radiative transfer of photons from the core of the sun to the surface (illustrating random walk), and through the atmosphere (illustrating the formation of absorption and emission lines).

4)The Classification Of Stellar Spectra Students practice classifying digital stellar spectra using an atlas of digitized spectra and unknowns. They then use a simulated optical telescope with a photon-counting spectrometer to obtain spectra of stars from a simulated star field, and by classifying the spectra they obtain the distance to the stars.

5) Photoelectric Photometry Of The Pleiades Students use a photon-counting photometer attached to a simulated telescope to obtain B and V magnitudes of stars in the Pleiades. They use their data to construct an HR diagram of the cluster and to determine the distance of the cluster.

6) The Hubble Redshift Distance Relation Students use a photon-counting spectrometer attached to a simulated telescope to obtain spectra of galaxies in five galaxy clusters at various distances from the Milky Way. By measuring the red-shifts of prominent spectral features they plot a Velocity-Distance graph, determine the Hubble constant, and calculate the expansion age of the universe.

7) The Large-Scale Structure of the Universe Students use a photon-counting spectrometer attached to a simulated telescope to obtain spectra of galaxies in a sample chosen from published large-scale surveys of a slice of nearby space. By measuring the red-shifts of prominent spectral features they plot a "wedge diagram" showing the three-dimensional distribution of the galaxies including the "Great Wall". Students can pool data gathered collaboratively using network software.

8) Radio Astronomy of Pulsars Students use a simulated steerable radio telescope to investigate the properties of pulsars. They measure period and amplitude of selected pulsars as a function of frequency. They then use multi-frequency observations to determine the distance of pulsars from the dispersion in arrival times of pulses.

9) Astrometry of Asteroids Students use a specialized image analysis program to blink pairs of images taken with a research telescope. They find asteroids as moving objects, measure the coordinates of the objects by using a digital catalog of reference stars (The Hubble Guide Star Catalog), and determine the angular velocity of the asteroid. They also measure the coordinates of the asteroid on two images taken simultaneously from sites several thousand km apart, and use the parallax to determine the distance and velocity of the asteroid. (Ratcliff et al, 1993).

A research version of the software used for the astrometry exercise, called "Toolkit for Astrometry" has also been developed. The software makes it easy to plan observations of asteroids, blink and measure large images from professional telescopes, and produce ephemerides and finding charts.


Next Section: Prospects for Future Development
Title/Abstract Page: The Universe on a
Previous Section: The Design Philosophy of
Contents Page: Volume 17, Number 2

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