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 Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

(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 harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

, and

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...

, 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, and by extension, the term is also sometimes used to describe the numerical solution of differential equations ...

shows that the orbit is stable. Kimmo A. Innanen and

Seppo Mikkola Seppo Mikkola (born 1947) is a Finnish astronomer. He is a senior lecturer at the University of Turku and staff member at Tuorla Observatory. Mikkola is a leading expert in celestial mechanics. He has made fundamental contributions to the theory ...

note that "contrary to intuition, there is clear

empirical evidence Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences ...

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 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 describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillat ...

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 Yorp or YORP may refer to one of the following: * 54509 YORP, an Earth co-orbital asteroid * Yarkovsky–O'Keefe–Radzievskii–Paddack effect, a second-order variation on the Yarkovsky effect *Yorps, friendly one-eyed Martians from the Commander ...

(consistent with its rotational period of 2.69 h). The

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

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 μm olivine feature and a very reddish spectrum shortwards of 0.7 μm. They are thought to come from the completely differentiated mantle of an asteroi ...

, but the visual spectrum is consistent with an evolved form of

achondrite An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystalli ...

called an angrite. A-class asteroids are tinted red in hue, with a moderate

albedo Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...

. 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 System Capitalization 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 "Solar ...

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 often colloquially referred to as ''moons'' ...

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.

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 * * {{DEFAULTSORT:005261 Mars trojans

Eureka Eureka (often abbreviated as E!, or Σ!) is an intergovernmental organisation for research and development funding and coordination. Eureka is an open platform for international cooperation in innovation. Organisations and companies applying th ...

Binary asteroids Sr-type asteroids (SMASS) 19900620

Satellite

See also

References

External links