is the ninth

Neptune trojan Neptune trojans are bodies that orbit the Sun near one of the stable Lagrangian points of Neptune, similar to the Trojan (astronomy), trojans of other planets. They therefore have approximately the same orbital period as Neptune and follow rough ...

discovered. It was first observed on 29 April 2011, during the New Horizons KBO Search using the Magellan II (Clay) Telescope at Las Campanas Observatory in Chile. It has the same orbital period as

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

and orbits at the

Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of th ...

about 60 ° backwards of Neptune.

Orbit and classification

Neptune trojans are

resonant trans-Neptunian object In astronomy, a resonant trans-Neptunian object is a trans-Neptunian object (TNO) in mean-motion orbital resonance with Neptune. The orbital periods of the resonant objects are in a simple integer relations with the period of Neptune, e.g. 1:2, 2 ...

s (TNO) in a 1:1 mean-motion orbital resonance with Neptune. These Trojans have a

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

(a) very similar Neptune's (30.10 AU). orbits the Sun with a semi-major axis of 30.219 AU at a distance of 27.7–32.8 AU once every 166 years and 1 month (60,675 days). Its orbit has an eccentricity of 0.08 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 29 ° with respect to the ecliptic. Among the first 17 Neptune trojans discovered so far, it is the one with the highest inclination.

Physical properties

Diameter and albedo

Based on a generic magnitude-to-diameter conversion, it measures approximately 100 kilometers in diameter using an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of 8.1 and an assumed

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, 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 ...

of 0.10. It is an averaged-sized body among the first 17 Neptune trojans discovered so far, which measure between 60 and 200 kilometers (for an absolute magnitude of 9.3–6.6 and an assumed albedo of 0.10).

Numbering and naming

Due to its orbital uncertainty, this

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...

has not been numbered and its official discoverers have not been determined. If named, it will follow the naming scheme already established with

385571 Otrera 385571 Otrera, provisional designation , is a Neptune trojan leading Neptune's orbit in the outer Solar System. It was discovered by American astronomers Scott Sheppard and Chad Trujillo at Las Campanas Observatory on 16 October 2004. It measures ...

, which is to name these objects after figures related to the

Amazons In Greek mythology, the Amazons (Ancient Greek: Ἀμαζόνες ''Amazónes'', singular Ἀμαζών ''Amazōn'', via Latin ''Amāzon, -ŏnis'') are portrayed in a number of ancient epic poems and legends, such as the Labours of Hercules, ...

, an all-female warrior tribe that fought in the

Trojan War In Greek mythology, the Trojan War was waged against the city of Troy by the Achaeans (Greeks) after Paris of Troy took Helen from her husband Menelaus, king of Sparta. The war is one of the most important events in Greek mythology and has ...

on the side of the Trojans against the Greek.

Exploration

In October 2012, was the closest known object of any kind to the ''

New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research ...

'' spacecraft. In mid- to late 2013, ''New Horizons'' passed within 1.2 AU of , where it would be detectable with one of the onboard instruments. An observation from ''New Horizons'' would measure the phase curve of at phase angles unobtainable 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 ...

. The ''New Horizons'' team eventually decided that they would not target for observations because the preparations for the Pluto approach took precedence.

References

External links

A. Parker – : A new companion for Neptune – TPS

YouTube video showing the orbital evolution

Discoverer comments

AstDyS-2
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