the plane of the ecliptic. Trojans do not orbit right at Lagrangian points but oscillate in tadpole-shaped loops around them (as viewed in a corotating reference frame in which the planet and Lagrangian points are stationary); traverses its loop over a period of 395 years. 's loop is so elongated that it sometimes travels nearly to the opposite side of the Sun with respect to Earth. Its movements do not bring it any closer to Earth than 20 million kilometers (12.4 million miles), which is more than 50 times the distance to the Moon. was at the near-Earth end of its tadpole in 2010–2011, which facilitated its discovery. 's orbit has a chaotic character, making long-range predictions difficult. Prior to 500 AD, it may have been oscillating about the Lagrangian point (60 degrees behind Earth), before jumping to via . Short-term unstable libration about , and transitions to horseshoe orbits are also possible. Newer calculations based on an improved orbit determination confirm these results. Accessibility from Earth Because Earth trojans share Earth's orbit and have little gravity of their own, less energy might be needed to reach them than the Moon, even though they are much more distant. However, is not an energetically attractive target for a space mission because of its orbital inclination: It moves so far above and below Earth's orbit that the required change in velocity for a spacecraft to match its trajectory coming from Earth's would be 9.4 km/s, whereas some other near-Earth asteroids require less than 4 km/s. During the 5 December 2012 Earth close approach of , the asteroid had an apparent magnitude of about 21. See also , the second Earth trojan discovered Claimed moons of Earth Provisional designation in astronomy, the naming convention used for astronomical objects immediately following their discovery Notes References External links MPC Database entry for NASA animation of its motion Alternate NASA animation of motion Minor planet object articles (unnumbered) 20101001