279 Thule
Encyclopedia
279 Thule is a large asteroid
from the asteroid belt
. It is classified as a D-type asteroid
and is probably composed of organic-rich silicate
s, carbon
and anhydrous
silicates.
The orbit of Thule is unusual. It orbits in the outermost edge of the asteroid belt in a 3:4 orbital resonance
with Jupiter
. Unlike the Hilda asteroids, whose eccentricities are fairly typical of asteroids of the asteroid belt, Thule has a very low eccentricity – actually much lower than that of Jupiter itself and only slightly higher than that of Earth
.
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 gap
s 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.
Thule was the first discovered member of the Thule dynamical group which as of 2008 is known to consist of three objects: 279 Thule, , and .
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.
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
from the asteroid belt
Asteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...
. It is classified as a D-type asteroid
D-type asteroid
D-type asteroids have a very low albedo and a featureless reddish electromagnetic spectrum. It has been suggested that they have a composition of organic rich silicates, carbon and anhydrous silicates, possibly with water ice in their interiors...
and is probably composed of organic-rich silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
s, carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
and anhydrous
Anhydrous
As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...
silicates.
The orbit of Thule is unusual. It orbits in the outermost edge of the asteroid belt in a 3:4 orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
with Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
. Unlike the Hilda asteroids, whose eccentricities are fairly typical of asteroids of the asteroid belt, Thule has a very low eccentricity – actually much lower than that of Jupiter itself and only slightly higher than that of Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
.
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 gap
Kirkwood gap
A Kirkwood gap is a gap or dip in the distribution of main-belt asteroids with semi-major axis , as seen in the histogram below...
s 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.
Thule was the first discovered member of the Thule dynamical group which as of 2008 is known to consist of three objects: 279 Thule, , and .
It was discovered by Johann Palisa
Johann Palisa
Johann Palisa was an Austrian astronomer, born in Opava in Austrian Silesia .He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 Gellivara in 1923...
on October 25, 1888 in Vienna
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...
and was named aptly after the ultimate northern land of Thule
Thule
Thule Greek: Θούλη, Thoulē), also spelled Thula, Thila, or Thyïlea, is, in classical European literature and maps, a region in the far north. Though often considered to be an island in antiquity, modern interpretations of what was meant by Thule often identify it as Norway. Other interpretations...
.
Thule was the first asteroid discovered with a semi-major axis greater than 4 AU.
External links
- Orbital simulation from JPL (Java) / Horizons Ephemeris