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A Simulation of the Kepler Mission

The Kepler Mission Education team has produced table top models demonstrating
the principle of how Kepler will find extrasolar planets by the transit method.
Components include:
  • Orrery† (model planet system),
  • Light (model star),
  • Light sensor†† (model Kepler photometer),
  • Computer interface (model Deep Space Network), and
  • Computer graphic software (model Kepler Science Office)

† The 1st orrery we created was one made of LEGO parts, described on this page. Later, an orrery was created for one of the investigations in the middle school Planetary Science course from the Full Option Science System (FOSS). That one is commercially available (photo below).

†† Commercial light sensors can be used (e.g. from companies such as Vernier and Pasco), and as an alternative, we have created free software to turn a webcam or your laptop camera into a "light sensor." See LightGrapher software.

2012: FOSS Orrery

Available as of 2012: FOSS Orrery
Photo of FOSS orrery
The FOSS orrery.

K'NEX 1-planet orrery image
K'NEX 1-planet orrery image
K'NEX Orrery

In spring of 2015, Ryan Mohta, 8th grade student at Hyde Middle School in Cupertino, CA, created a model using K'NEX and Java programming to demonstrate how exoplanets are found using the transit method.


Components of transit demo setup
Components of Transit Demo Setup
LEGO Orrery

Download detailed instructions:
Alas, there is no LEGO kit for this orrery. Refer to parts lists below to acquire the needed LEGO parts.
The Kepler LEGO orrery 2008-2009 teacher workshop version.
The Kepler LEGO orrery 2008-2009 teacher workshop version.
See also:
  • Using LEGO orreries in a college astronomy lab, an interview with Doug Duncan, University of Colorado.
  • A demonstration of the Kepler LEGO Orrery by Ruth Craft of Kennedy High School on a PBS TV program called Outdoor Elements. See segment #3 of "Far Out! Telescopes" (Episode #1003) at
  • 8-body LEGO Orrery.
  • Gadsden State Community College instructor, Brian Geislinger, devised a model star system in the lab to show his students how professional astronomers gain much information just from the light that is projected from across the universe. The model solar system was set up with light bulbs placed in an enclosed wooden box. Students gather data using a Vernier Light Sensor: light bulbs dimmed and brightened at varying speeds and intensities in order to mimic the light patterns of Cepheid variable stars, supernovas, and rotating planets; motors swinging artificial ‘planets’ around their light bulb-powered Suns.

The 4-planet LEGO orrery devised by Dave Koch, Kepler Deputy PI

4 planet orrery

Comments from Koch, September 2005:

I made modifications to nearly every part of the model so it is more robust: the base has more blocks, the crank handle has bigger blocks, the outer two planets have their beam ends positively captured rather than just stuck on and do not flex as much. The inner most planet's beam is centered. etc.

Orrery 2

For the outer most planet, I found that the Lego set has a white gear without any knobs on it. The knobs are what were jamming in the first generation design. I then put extra spacers on the shafts. The smooth gear doesn't need the spacers so they came out making the gear box for the outer planet more compact.

Orrery 3

The Moon:
This is very easy to add to the current design. It just involves adding the 4 gear pairs to the existing second planet beam. (I really wanted to use up more of the parts from the Lego set.) The moon I made simply by putting a few coats of white nail polish on the head of a pin. I then heat the end of the pin with a match until it glows red hot and then quickly stick it into the Lego post.

LEGO Orrery with 8 bodies: 5 planets and 3 moons, by Robert Munafo

5 planet orrery
This model has more irregular orbit periods, and is constructed entirely out of parts from LEGO sets 8273 (Off Road Truck, $50) and 8287 (Motor Set, $30) with 12-, 20-, and 36-tooth gears, and a red transmission adapter ring essential for getting a 5th planet.

See Video

Older versions: