279 Thule

Minor Planet | name=279 Thule
discoverer=Johann Palisa
discovery_date=October 25, 1888
designations=
category=Main belt (Thule)
epoch=30 January, 2005 (JD 2453400.5)
semimajor=639.809 Gm (4.277 AU)
perihelion=631.907 Gm (4.224 AU)
aphelion=647.712 Gm (4.33 AU)
eccentricity=0.012
period=3230.561 d (8.84 a)
inclination=2.338°
asc_node=73.642°
arg_peri=82.821°
mean_anomaly=274.796°
speed=14.4 km/s
dimensions=127.0 km
mass="unknown"
density="unknown"
gravity="unknown"
escape_velocity="unknown"
rotation="unknown"
spectral_class=D
abs_mag=8.57
albedo="unknown"
temperature="unknown"

279 Thule (pronEng|ˈθjuːli "thew'-lee") is a very large Main belt asteroid. It is classified as a D-type asteroid and is probably composed of organic rich silicates, carbon and anhydrous silicates.

The orbit of Thule is unusual. It appears to orbit in the outermost edge of the Main belt in a 3:4 orbital resonance with planet Jupiter. Unlike the Hilda asteroids whose eccentricity is fairly typical of main belt asteroids, Thule has a very low eccentricity - actually much lower that that of Jupiter itself and only slightly higher than that of Earth. The origin of 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 precisely the distance from the Sun Thule does, in the same way (though with the reverse effect) as the Kirkwood gaps in the more inner parts of the asteroid belt. It could thus be that the resonance which holds Thule in an extremely low-eccentricity orbit serves to eject other smaller bodies whose distance from the Sun is only slightly different from that of Thule itself.

It is the sole member of the Thule dynamical group.

It was discovered by Johann Palisa on October 25, 1888 in Vienna and was named aptly after the ultimate northern land of Thule.

Thule was the first asteroid discovered with a semi-major axis greater than 4 AU.

External links

* [http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=279 279 Thule] on NASA/JPL Small-Body Database
* [http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=279;orb=1 Orbital simulation] from JPL (Java) / [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=279 Horizons Ephemeris]