an existing asteroid; examples of Arjunas include 1991 VG. Earth trojans are asteroids located in the Earth–Sun Lagrangian points and . Their location in the sky as observed from Earth's surface would be fixed at about 60 degrees east and west of the Sun, and as people tend to search for asteroids at much greater elongations few searches have been done in these locations. The only known Earth trojan is . Near-Earth asteroids is a catch-all term for asteroids whose orbit closely approaches that of Earth. It includes almost all of the above groups, as well as the Amor asteroids. Groups out to the orbit of Mars The Amor asteroids, named after 1221 Amor, are near-Earth asteroids that are not Earth-crossers, having a perihelion just outside the Earth's orbit. Mars-crosser asteroids have orbits that cross that of Mars, but do not necessarily closely approach the Earth's. Mars trojans follow or lead Mars on its orbit, at either of the two Lagrangian points 60° ahead () or behind (). As of November 2020, nine are known. The largest appears to be 5261 Eureka. Many of the Earth-, Venus-, and Mercury-crosser asteroids have aphelia greater than 1 AU. The asteroid belt The overwhelming majority of known asteroids have orbits lying between the orbits of Mars and Jupiter, roughly between 2 and 4 AU. These could not form a planet due to the gravitational influence of Jupiter. Jupiter's gravitational influence, through orbital resonance, clears Kirkwood gaps in the asteroid belt, first recognised by Daniel Kirkwood in 1874. The region with the densest concentration (lying between the Kirkwood gaps at 2.06 and 3.27 AU, with eccentricities below about 0.3, and inclinations smaller than 30°) is called the asteroid belt. It can be further subdivided by the Kirkwood Gaps into the: Inner asteroid belt, inside of the strong Kirkwood gap at 2.50 AU due to the 3:1 Jupiter orbital resonance. The largest member is 4 Vesta. It apparently also includes a group called the main-belt I asteroids which have a semi-major axis between 2.3 AU and 2.5 AU and an inclination of less than 18°. Middle (or intermediate) asteroid belt, between the 3:1 and 5:2 Jupiter orbital resonances, the latter at 2.82 AU. The largest member is Ceres. This group is apparently split into the: Main-belt IIa asteroids which have a semi-major axis between 2.5 AU and 2.706 AU and an inclination less than 33°.