279 Thule is a very big Main belt asteroid. It is classified as a D-type asteroid and is probably made of organic rich silicates, carbon and anhydrous silicates.
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.
Some astronomers have argued that Thule's present orbit is the natural result of the force of Jupiter on a body orbiting at exactly the distance from the Sun Thule does, in the same way (though with the reverse effect) as the Kirkwood gaps in the more closer parts of the asteroid belt. It could thus be that the resonance which holds Thule in a very low-eccentricity orbit serves to eject other smaller bodies whose distance from the Sun is only a bit different from that of Thule itself.
It is the main member of the Thule dynamical group.
It was found by Johann Palisa on October 25, 1888 in Vienna and was named aptly after the ultimate northern land of Thule.
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