The orbit of Thule is unusual. It appears to orbit in the farthest edge of the Main belt in a 3:4 orbital resonance with planet Jupiter. Unlike the Hilda asteroids whose eccentricity is fairly common of main belt asteroids, Thule has a very low eccentricity - actually much lower than that of Jupiter itself and only a bit higher than that of Earth. Why it has this orbit is not clear, as is the reason for the absence of smaller bodies in similar 4:3 resonances with Jupiter.