On January 28, 1986, the Space Shuttle Challenger exploded 73 seconds after liftoff from the Kennedy Space Center in Florida. The Colorado Scale Model Solar System is dedicated to the memory of Challenger astronaut, and University of Colorado alumnus,

Ellison S. Onizuka
B.S., M.S. (Aerospace Engineering), CU 1969

and the other six Challenger astronauts:

Gregory B. Jarvis
S. Christa McAuliffe
Ronald E. McNair
Judith A. Resnik
Francis R. Scobee
Michael J. Smith

This photograph, taken from in front of the Fiske Planetarium, shows the inner solar system in the Colorado model. The Sun is the gold sphere atop the pyramid. The black granite pedestal to the left of the Sun in the photo holds Mercury, and the three pedestals visible to the right of the Sun hold Venus, Earth, and Mars, respectively. All the inner planets are pinhead-size or smaller on this scale. The street, Regent Drive, corresponds roughly to the location of the asteroid belt. The outer planets, not visible in the photo, can be found along the pathway that continues across the street.
(Photo by Keith Gleason, Sommers-Bausch Obervatory)

The Colorado Scale Model Solar System is located on the campus of the University of Colorado, Boulder.

About the model
The Colorado Scale Model Solar System shows both planetary sizes and distances in our solar system at 1 ten-billionth actual size. (I.e., model scale is 1 to 10 billion.) The Sun and inner planets are located in front of Fiske Planetarium on the campus of the University of Colorado, Boulder. The Colorado model is one of only a handful of walkable scale model solar systems in the world that use a true scale; that is, models that have the same scale for both diameters and distances.

Some interesting facts illustrated in the model
The Sun is roughly the size of a grapefruit (14 cm diameter), while the planets range in size from dust-speck-size Pluto to marble-size Jupiter. Earth is about the size of a pinhead (1.3 mm diameter).

The inner planets (Mercury, Venus, Earth, Mars) are all located within a couple dozen steps of the sun, with the Earth located 15 meters from the Sun. The outer planets (Jupiter, Saturn, Uranus, Neptune, Pluto) are spread much farther apart with Pluto located about 600 meters (just over 1/3 mile) from the Sun. Walking the full length of the model would take about ten minutes, not including stops.

You can fit the Earth and the entire orbit of the Moon in the palm of your hand -- which represents the farthest humans have ever traveled.

On this same scale, the nearest stars besides the Sun are more than 4,000 kilometers (2,500 miles) away -- roughly the distance from Boulder to the Panama Canal.

Origins of the model
The model was originally created by Tom Ayres, Ken Center, Ron Bass, Matt Carter, and myself (Jeff Bennett); we began work in 1984 and it was dedicated in May 1987. The idea for the model grew out of my experience teaching both at elementary and college levels. In 1993, the model was refurbished largely through the efforts of Tom Ayres, Jodi Schoemer, and Mike Verplanck.

Model Solar Systems Beyond Colorado
The Colorado Scale Model Solar System provided the impetus for the Smithsonian Institution, the Challenger Center for Space Science Education, and NASA to create Voyage, a much more dramatic scale model solar system with color images and planets embedded in glass. The first Voyage model opened on the National Mall in Washington, DC, on October 17, 2001. With luck and adequate funding, Voyage replicas will then spread to dozens of other sites around the world.