(121514) 1999 UJ7 on:
[Wikipedia]
[Google]
[Amazon]
is a small
orbits around the of Mars in a very stable orbit and is large enough that the
asteroid
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere.
...
orbiting near the of Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...
(60 degrees ahead Mars on its orbit). As of September 2011, it is the only known asteroid to orbit the leading of Mars, although at least three other asteroids orbit Mars's trailing : 5261 Eureka
5261 Eureka is the first Mars trojan discovered. It was discovered by David H. Levy and Henry Holt at Palomar Observatory on 20 June 1990. It trails Mars (at the ) at a distance varying by only 0.3 AU during each revolution (with a secular t ...
, , and . Not only does orbit on the other side of Mars from other similar asteroids, its spectrum
A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...
is different as well, which is puzzling because all of the Martian
Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. It became the most popular celestial object in fiction in the late 1800s as the Moon was evidently lifeless. At the time, the pred ...
trojans
Trojan or Trojans may refer to:
* Of or from the ancient city of Troy
* Trojan language, the language of the historical Trojans
Arts and entertainment Music
* ''Les Troyens'' ('The Trojans'), an opera by Berlioz, premiered part 1863, part 1890 ...
seem to be in very stable orbits.
Orbit
orbits around the of Mars in a very stable orbit and is large enough that the Yarkovsky effect
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum. It is usually considered in relation to meteoroids or small asteroids (about 10 cm to 10 km i ...
will not affect its orbit.
Physical characteristics
Due to similarity in the measured brightness of with other Martian trojans, it is thought to be a small asteroid with an effective diameter on the order of . Its spectrum suggests that it is anX-type asteroid The X-group of asteroids collects together several types with similar spectra, but probably quite different compositions.
Tholen classification
In the Tholen classification the X-group consists of the following types:
* E-type – with high al ...
, which is different from 5261 Eureka and , and is somewhat puzzling since different mineral compositions suggest different origins for the two groups of asteroids. The long lifetime of the orbits for these asteroids makes the possibility of one or more of them being interlopers unlikely, however. This suggests that either one or more of the Martian trojans was captured in such a way as to give it a long-term stable orbit (and it is therefore not a primordial Martian asteroid), or that some fusion or combination of previous asteroids resulted in the presently observed ones. The Yarkovsky effect may provide a potential capture mechanism but not enough is known about the shapes of these objects to provide a useful Yarkovsky model.
See also
*5261 Eureka
5261 Eureka is the first Mars trojan discovered. It was discovered by David H. Levy and Henry Holt at Palomar Observatory on 20 June 1990. It trails Mars (at the ) at a distance varying by only 0.3 AU during each revolution (with a secular t ...
(1990 MB)
*
*
*
*
*
*
*
*
*
*
*
*
*
References
External links
* * {{DEFAULTSORT:1999 UJ7 121514 121514 121514 19991030