|Appears in (anime)|
The Planetary Particle, also known as the Yusei Project, was the essential particle which ultimately lead to the development of Ener-D technology. This gear is inspired from the real-life epicyclic gearing system.
The project was founded by Dr. Fudo 17 years prior to the Yu-Gi-Oh! 5D's plot, as according to Roman Goodwin, he was the leading man when it came to Quantum Physics. The project in which involved this particle, consisted of a planetary gear which has the task of binding particles together onto other particles. Unbeknownst to the Professor, this would cause him to stumble upon the technology that lead to the creation of the Ener-D reactor. As this particle would be the one needed to complete it.
Dr. Fudo named his son, Yusei, after this gear (In the Japanese version the gear's name is pronuonced Yusei gear), as he wanted him to be a person who could connect people through bonds just like the gear does.
More importantly, according to Bruno, the Planetary particle is a living energy that can read people's hearts. He states that Dr. Fudo and Roman realized this fact as they were in charge of working with Ener-D. The fact that people's hearts vary from one another according to Bruno has already been seen. Because of the good in people's hearts is how the Crimson Dragon appeared in the first place, while the evil in others is what called forth the Earthbound Immortals.
When riding a Duel Runner at very high speeds while being totally focused, it is possible to control the Ener-D produced by the Planetary Particles that each Duel Runner has. This allows the user to reach the Clear Mind state and perform an Accel Synchro Summon.
The Ark Cradle has a giant Planetary Particle inside, but it spins in reverse so it produces negative Ener-D.