Motion in the Solar System

This applet knows where some things in the Solar System (and beyond) are. You can use it to explore a number of astronomical phenomena.
You can choose where you are from the first pop-up menu, and what you are looking at from the second. If the two are not the same, you can choose the latitude where you are; if they are the same, the latitude scroll bar becomes a "z" scroll bar, allowing you to view the body from above or below. When the "from" and "viewing" targets are different and you are viewing from a planet, you may choose either geocentric or heliocentric views. The applet begins in "heliocentric" mode, meaning you are looking at the sky in flat projection, with the latitude relative to the plane of the Solar System; as you change the date and time, or animate, you will always be at the first object, viewing the second object. In "geocentric" mode, you are viewing from the first object, but seeing the sky in polar projection (as if you were standing on the Earth).

The date and time scroll bars allow you to see the sky at a specific date and time. You can also draw and erase line-of-sight markers using the appropriate buttons, but they are only drawn when the "from" and "viewing" targets are the same.

When the "from" and "viewing" targets are different, the coordinates represent angles and the lattice lines are drawn every 15 degrees. When the "from" and "viewing" targets are the same, the coordinates are distance. All times are Universal Time.

It's a little complicated, but it's a powerful little program. Even the author hasn't fully explored its possibilities...

You need a Java-capable browser to be able to use the applets. If they do not work with your Windows system, download the Java VM (Virtual Machine) for your version of Windows at the download section at

You can use it to explore the following phenomena:

©2013, Kenneth R. Koehler. All Rights Reserved. This document may be freely reproduced provided that this copyright notice is included.

Please send comments or suggestions to the author.