5261 Eureka is the first
Mars trojan
The Mars trojans are a group of trojan objects that share the orbit of the planet Mars around the Sun. They can be found around the two Lagrangian points 60° ahead of and behind Mars. The origin of the Mars trojans is not well understood. One t ...
discovered.
It was discovered by
David H. Levy
David Howard Levy (born May 22, 1948) is a Canadian amateur astronomer, science writer and discoverer of comets and minor planets, who co-discovered Comet Shoemaker–Levy 9 in 1993, which collided with the planet Jupiter in 1994.
Biography
L ...
and Henry Holt at
Palomar Observatory
Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...
on 20 June 1990.
It trails
Mars (at the ) at a distance varying by only 0.3
AU during each revolution (with a
secular trend
The secular variation of a time series is its long-term, non-periodic variation (see decomposition of time series). Whether a variation is perceived as secular or not depends on the available timescale: a variation that is secular over a timescale ...
superimposed, changing the distance from 1.5–1.8 AU around 1850 to 1.3–1.6 AU around 2400). Minimum distances from
Earth,
Venus, and
Jupiter, are 0.5, 0.8, and 3.5 AU, respectively.
Long-term
numerical integration shows that the orbit is stable.
Kimmo A. Innanen and
Seppo Mikkola note that "contrary to intuition, there is clear
empirical evidence for the stability of motion around the and points of all the terrestrial planets over a timeframe of several million years".
Since the discovery of 5261 Eureka, the
Minor Planet Center
The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory.
Function
...
has recognized three other asteroids as Martian trojans: at the point, at the point,
[ and , also at the point. At least five other asteroids in near-1:1 resonances with Mars have been discovered, but they do not exhibit trojan behavior. They are , , (36017) 1999 ND43, and (152704) 1998 SD4. Due to close orbital similarities, most of the other, smaller, members of the L5 group are hypothesized to be fragments of 5261 Eureka that were detached after it was spun up by the YORP effect (consistent with its rotational period of 2.69 h).]angrite
Angrites are a rare group of achondrites consisting mostly of Al-Ti bearing diopside, hedenbergite, olivine, anorthite and troilite with minor traces of phosphate and metals. The group is named for the Angra dos Reis meteorite. They are the olde ...
. A-class asteroids are tinted red in hue, with a moderate albedo. The asteroid is located deep within a stable Lagrangian zone of Mars, which is considered indicative of a primordial origin—meaning the asteroid has most likely been in this orbit for much of the history of the Solar System.
Satellite
On 28 November 2011, a natural satellite of 5261 Eureka was found. It has yet to be named, and its provisional designation is S/2011 (5261) 1. The moon is about 0.46 km in diameter and orbits 2.1 km from Eureka. The satellite's existence was announced in September 2014.
See also
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References
;Further reading
IAUC 5045
* A. S. Rivkin, R. P. Binzel, S. J. Bus, and J. A. Grier, "Spectroscopy and Classification of Mars Trojan Asteroids", ''Bulletin of the American Astronomical Society'' 34, 2002, p. 840.
* S. Tabachnik and N. W. Evans, "Cartography for Martian Trojans", ''The Astrophysical Journal'' 517, 1999, pp. L63–L66.
External links
The co-orbital asteroids of Mars
A simulation and animation showing Mars's co-orbital and near co-orbital asteroids
Robert Johnston, johnstonsarchive.net
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{{DEFAULTSORT:005261
Mars trojans
Eureka
Eureka
Eureka
Binary asteroids
Sr-type asteroids (SMASS)
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