This Astronomical Parallax 3D Model illustrates the phenomenon of annual stellar parallax in astronomy. Parallax is the apparent displacement of an object relative to the background that is caused by the motion of the observer (rather than the motion of the object itself, or of the background). This simulation illustrates the parallax of an object in space that results from the Earth's annual orbital motion.

The Space View window shows the Earth (blue point) orbiting the Sun (organe point). The white point represents a stationary star. The open white circle shows the location of the object on the celestial sphere as seen from the Sun.  The magenta point shows the location of the star on the celestial sphere as seen by an observer on the orbiting Earth. Various options allow the user to display the line of sight from Earth through the star, the line from the Sun through the star, cardinal direction arrows, the trace of the star's apparent motion, the trace of Earth's orbit, and the planes and axes of the celestial equator and ecliptic. Controls allow the user to adjust the distance to the star as well as its celestial coordinates (as seen from the Sun). Another menu allows the user to select a particular day (equinox or solstice) of the year.

The Sky View window shows the apparent location of the star on the sky as seen by an Earth observer. The "true location" (the location as seen from the Sun) is shown as an open white circle, while the apparent location is shown as a magenta disk.

Note that some features have been simplified or exaggerated. The Earth's orbit is treated as a circle. The distances to the "star" are vastly smaller than the distance to any real star (at the distance to the nearest real star the annual parallax would be imperceptible in this simulation). The size of the Earth, sun, and star are exaggerated so as to make them visible on the scale of the simulation.

Please note that this resource requires at least version 1.5 of Java (JRE).