279 Thule is a large asteroid from the outer asteroid belt. It was discovered by Austrian astronomer Johann Palisa on 25 October 1888 in Vienna. This body was named after the ultimate northern land of Thule, according to ancient Greek and Roman lore.
This asteroid orbits the Sun at a distance of , with an eccentricity of 0.026 and an orbital period of 9.07 years. The orbital plane is inclined at an angle of 2.32° to the plane of the ecliptic. Thule was the first asteroid discovered with a semi-major axis greater than 4 AU. It is the only large asteroid with a 4:3 resonance orbital with Jupiter that also has a small eccentricity and orbital inclination.
279 Thule is classified as a D-type asteroid and is probably composed of organic-rich silicates, carbon and anhydrous silicates. Based on infrared measurements, it spans a diameter of approximately .
Thule asteroids
Thule was the first discovered member of the Thule dynamical group, which as of 2008 was known to consist of three objects: 279 Thule, , and . The orbits of these bodies are unusual. They orbit in the outermost edge of the asteroid belt in a 4:3 orbital resonance with Jupiter, the result of the periodic force Jupiter exerts on a body with Thule's orbital period, in the same way (though with the reverse effect) as the Kirkwood gaps in the more inner parts of the asteroid belt.
+Known members as of May 2021Namesemimajor axis (au)period (years)eccentricityinclination (°)absolute magnitudeSize (km)279 Thule 4.269 8.82 0.0432 2.334 8.53 4.290 8.89 0.1335 7.132 13.84 4.278 8.85 0.2513 3.238 14.53 4.286 8.87 0.0465 5.501 15.1 4.288 8.88 0.1161 3.497 15.49 4.297 8.91 0.2312 3.193 15.5 4.283 8.86 0.3722 5.935 16.5
See also 486958 Arrokoth – A Kuiper belt object formerly nicknamed Ultima Thule
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