Simple demonstration of the concept of the annual parallax of stars.
This processing sketch implements an animation that provides a very basic illustration of the concept of the annual parallax of a star. The screen-shot below shows what the animation looks like.
The left part of the image shows the earth going around the sun and how the line of sight between the earth and a nearby star (yellow star symbol) varies, leading to an apparent annual change of position with respect to the more distant stars.
The box to the top right shows what the 3D situation on the left looks like, projected on the sky. The star goes round in circles with respect to the background stars, a reflection of the motion of the earth around the sun.
At the bottom right a scroll-bar can be seen that can be used to adjust the distance to the star (in light year). The value of the distance and corresponding parallax angle (in arcsecond) are shown above the scroll-bar.
The animation is a recreation in the Processing language of a Flash animation created by ESA. The latter is no longer available for download and the Flash format is not supported anymore, hence the effort to recreate the parallax demonstration in Processing.
The animation is intended for use during presentations; to provide a simple but effective demonstration of the concept of the annual parallax of a star. From within the Processing development environment the sketch can be exported as a stand-alone executable (with the Java Runtime Environment included), which can be used on any platform (famous last words...).
You can set the language for the text in the animation at the top of the ParallaxDemo code.
To run the sketch in full-screen mode uncomment the relevant line in the
setup { ... } code block.
Save a screen-shot of the running sketch by pressing the right mouse button.
The texture image for the earth is from the examples folder in the Processing distribution (TextureSphere example). The texture image for the sun is from https://commons.wikimedia.org/wiki/File:Map_of_the_full_sun.jpg.
