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 and Henry Holt at
Palomar Observatory
The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...
on 20 June 1990.
It trails
Mars
Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
(at the ) at a distance varying by only 0.3
AU during each revolution (with a
secular trend superimposed, changing the distance from 1.5–1.8 AU around 1850 to 1.3–1.6 AU around 2400). Minimum distances from
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
,
Venus
Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
, and
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
, are 0.5, 0.8, and 3.5 AU, respectively.
Long-term
numerical integration
In analysis, numerical integration comprises a broad family of algorithms for calculating the numerical value of a definite integral.
The term numerical quadrature (often abbreviated to quadrature) is more or less a synonym for "numerical integr ...
shows that the orbit is stable.
Kimmo A. Innanen and
Seppo Mikkola note that "contrary to intuition, there is clear
empirical evidence
Empirical evidence is evidence obtained through sense experience or experimental procedure. It is of central importance to the sciences and plays a role in various other fields, like epistemology and law.
There is no general agreement on how the ...
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.
Funct ...
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
Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...
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).infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
spectrum for 5261 Eureka is typical for an A-type asteroid A-type asteroids are relatively uncommon inner-belt asteroids that have a strong, broad 1 micrometre, μm olivine feature and a very reddish spectrum shortwards of 0.7 μm. They are thought to come from the completely differentiated Mantle (geo ...
, but the visual spectrum is consistent with an evolved form of achondrite called an angrite. A-class asteroids are tinted red in hue, with a moderate albedo
Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...
. 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
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
.
Satellite
On 28 November 2011, a natural satellite
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are colloquially referred to as moons, a deriv ...
of 5261 Eureka was found. This unnamed 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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