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Trojan Asteroid – Computer generated image of TK7, Earth’s Trojan asteroid. The white dot is the asteroid, the green line is the path.

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Trojan Asteriods by Thomas Bare

Hello, my name is Thomas Bare. Today I will explain what a Trojan asteroid is and about some of the Trojan asteroids in our solar system.

A Trojan asteroid is an asteroid that is being pulled by the gravity of the Sun and a planet to keep it in the same orbit around the Sun as the planet. There are five points around the Sun in reference to a planet that the gravitational pull of the planet and the Sun balance each other out. These points are called Lagrangian points. The Lagrangian points are named L1, L2, L3, L4, and L5. Trojan asteroids are found at L4 and L5. These points are 60° away from the planet on its orbital path.L4 and L5 are also the only two Lagrangian points that the forces of gravity acting on it are all pulling in directions away from the point and not across it.

There are thousands of known Trojans following and proceeding Jupiter’s orbit. It is estimated that there might be as many Trojans as there are asteroids in the main asteroid belt.Very recently in 2010 the first Earth Trojan was found. This asteroid was named 2010 TK7. It hasn’t been found until now because it is always on the side of the Earth that faces the Sun.  There is only a short amount of time that telescopes on the ground can look for these asteroids. The times of day to look would be near morning for the L4 region and evening twilight for the L5 region.


Yang B, Lucey P, Glotch T. 2012. Are Large Trojan Asteroids Salty? An Observational, Theoretical, and Experimental Study. Icarus Vol. 223 Issue 1, p359-366. 8p.

Todd M, Tanga P, Coward D. 2012. An optimal Earth Trojan asteroid search strategy. Monthly Notices of the Royal Astronomical Society Vol. 420 Issue 1, pL28-L32.