You will need a Java capable browser to view these sites. These are graphic and multimedia computer simulations of astrophysical processes and objects. A QuickTime plug-in is needed for the lunar phases animation.

Solar System

This applet represents the solar system, including the four major moons of Jupiter and our own, and a couple of comets.

Solar Eclipse

The total solar eclipse of March 8/9 1997 was visible from eastern Siberia, with a partial eclipse observable from a much larger area, including China, Japan, and Alaska.

Hale-Bopp Comet

Comet Hale-Bopp was discovered on Saturday night July 22, 1995 by Alan Hale from Cloudcroft, New Mexico. His discovery was immediately followed about five minutes later by Tom Bopp from Phoenix, Arizona, giving them shared credit for the comet's discovery. The comet was at that time in the constellation Sagitarrius and approximately 7.15 AU from Sun (about 665 million miles). A pre-discovery image was found on a photographic plate made by Robert McNaught at Siding Springs, Australia taken April, 27, 1993. At this time the comet was at 13.1 AU from the Sun. Possibly this is intrinsically the brightest comet in human history. Only the Great Comet of 1811 was a comparable object.

Partial Lunar Eclipse

The partial lunar eclipse ofr March 23/24 1997 was visible from all of North America, but was best observed from the eastern seaboard.

Lunar Phases QuickTime

This is an animation showing the geometry of Earth, Moon, and Sun that gives us the differing phases of the Moon.

Stellar Evolution Simulation

The determining factor in the life of a star is its mass. The more massive a star the greater its energy output and the faster it evolves (changes). The about figure shows the temperature-luminosity relation for stars. This is known as the the Hertzsprung-Russell diagram. Stars on the main-sequence generate energy by converting (via fusion) hydrogen into helium. As stars use up their hydrogen fuel, they evolve off the main-sequence into the giant or supergiant phase. During these stages stars may "burn" helium or other even heavier elements as the core of the star reaches higher and higher temperatures and densities. How far this process proceeds depends on the initial mass of the star. The lowest mass stars will never go beyond hydrogen burning while the highest mass stars can produce elements all the way up to iron in their cores.

Binary Stars Simulation

Allows you to set the masses, orbital separation, orbital eccentricity, the inclination angle to our line of sight, and the angle of the nodes of an orbiting star pair. You see the privileged (from above the orbit) and the earth view of the system (which depends on the inclination angle). The observed velocities of the two stars, and the Doppler shifted spectral lines (as seen against the combined continuum from the two stars) are also shown in the upper right box. The spectral lines associated with each star are indicated and the unshifted line positions are also marked. The movement of the spectral lines against the continuum has been greatly exaggerated for display purposes, and the difference in brightness of the two stars has been ignored.

Eclipsing Binaries

Orbiting stars which are separated by a small distance may pass in front of one another. It is not possible for astronomers to see the individual stars, but there will be a change in the total light coming from the two stars when they "eclipse" one another. This simulation shows how this eclipse happens.

AJ's Cosmic Thing

AJ's Cosmic Thing is a robust, full-featured sky plotter applet, capable of rendering moving, interactive full-sky plots of brighter sky objects, as seen from any point on earth.

NASA Orbit Sims: Kepler's Three Laws

In the 16th century, the Polish astronomer Nicolaus Copernicus replaced the traditional Earth-centered view of planetary motion with one in which the Sun is at the center and the planets move around it in circles. Although the Copernican model came quite close to correctly predicting planetary motion, discrepancies existed. This became particularly evident in the case of the planet Mars, whose orbit was very accurately measured by the Danish astronomer Tycho Brahe. The problem was solved by the German mathematician Johannes Kepler, who found that planetary orbits are not circles, but ellipses. Kepler described planetary motion according to three laws. Each of these laws is illustrated by an applet.