279 Thule

outer main-belt asteroid

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.

279 Thule
Discovered byJohann Palisa
Discovery date25 October 1888
MPC designation(279) Thule
Pronunciation/ˈθjli/ THEW-lee[2]
1927 EC, 1954 FF, A920 GA, A923 RA[1]
Asteroid belt (Thule)
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc125.34 yr (45780 d)
Aphelion4.4617880 AU (667.47398 Gm)
Perihelion4.2367660 AU (633.81117 Gm)
4.3492770 AU (650.64258 Gm)
9.07 yr (3313.0 d)
0° 6m 31.184s / day
Physical characteristics
Dimensions126.59±3.7 km (IRAS)[1]
23.896 h (0.9957 d)[1]
Temperature133 K
D (Tholen)[1]

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.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 "279 Thule". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 11 May 2016.
  2. "Thule". Oxford English Dictionary second edition. Oxford University Press. 1989. Retrieved 7 December 2018.

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