9142 Rhesus is a larger

Jupiter trojan The Jupiter trojans, commonly called trojan asteroids or simply trojans, are a large group of asteroids that share the planet Jupiter's orbit around the Sun. Relative to Jupiter, each trojan librates around one of Jupiter's stable Lagrange poin ...

from the

Trojan camp This is a list of Jupiter trojans that lie in the Trojan camp, an elongated curved region around the trailing Lagrangian point, 60° behind Jupiter. All the asteroids at the trailing point have names corresponding to participants on the Troj ...

, approximately in diameter. It was discovered during the third Palomar–Leiden Trojan survey in 1977, and later named after King Rhesus from Greek mythology. The dark

D-type asteroid D-type asteroids have a very low albedo and a featureless reddish Asteroid spectral types, spectrum. It has been suggested that they have a composition of organic-rich silicates, carbon and anhydrous silicates, possibly with water ice in their inte ...

has a

rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

of 7.3 hours.

Discovery

''Rhesus'' was discovered on 16 October 1977, by Dutch astronomer couple

Ingrid Ingrid may refer to: * Ingrid (given name) * Ingrid (record label), and artist collective * Ingrid Burley, rapper known mononymously as Ingrid * Tropical Storm Ingrid, various cyclones * 1026 Ingrid, an asteroid * InGrid, the grid computing project ...

and

Cornelis van Houten Cornelis Johannes van Houten (18 February 1920 – 24 August 2002) was a Dutch astronomer, sometimes referred to as Kees van Houten. Early life and education Born in The Hague, he spent his entire career at Leiden University except for a brief p ...

at Leiden, on

photographic plate Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinn ...

s taken by Dutch–American astronomer

Tom Gehrels Anton M.J. "Tom" Gehrels (February 21, 1925 – July 11, 2011) was a Dutch–American astronomer, Professor of Planetary Sciences, and Astronomer at the University of Arizona, Tucson. Biography Youth and education Gehrels was born at Haa ...

at the

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 ...

in California. The body's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

begins with its first observation, a

precovery In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of an object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This happens mos ...

taken at Palomar in December 1954.

Palomar–Leiden survey

The

survey designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

"T-3" stands for the third Palomar–Leiden Trojan survey, named after the fruitful collaboration of the Palomar and

Leiden Observatory Leiden Observatory ( nl, Sterrewacht Leiden) is an astronomical institute of Leiden University, in the Netherlands. Established in 1633 to house the quadrant of Rudolph Snellius, it is the oldest operating university observatory in the world, with ...

in the 1960s and 1970s. Gehrels used Palomar's

Samuel Oschin telescope The Samuel Oschin telescope, also called the Oschin Schmidt, is a Schmidt camera at the Palomar Observatory in northern San Diego County, California. It consists of a 49.75-inch Schmidt corrector plate and a 72-inch (f/2.5) mirror. The instrument ...

(also known as the 48-inch Schmidt Telescope), and shipped the photographic plates to Ingrid and Cornelis van Houten at Leiden Observatory where

astrometry Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. His ...

was carried out. The trio are credited with the discovery of several thousand asteroids.

Orbit and classification

''Rhesus'' is a dark Jovian

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. ...

in a 1:1

orbital resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...

with Jupiter. It is located in the trailering

at the Gas Giant's

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 ...

, 60 ° behind its orbit . It orbits the Sun at a distance of 4.5–5.8 AU once every 11 years and 9 months (4,295 days;

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 ...

of 5.17 AU). Its orbit has an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

of 0.13 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 13 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...

Naming

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 ...

was named from

Greek mythology A major branch of classical mythology, Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical co ...

after King

Rhesus of Thrace Rhesus (; Ancient Greek: Ῥῆσος ''Rhêsos'') is a mythical Thracian king in ''Iliad'', Book X, who fought on the side of Trojans. Diomedes and Odysseus stole his team of fine horses during a night raid on the Trojan camp. Etymology His n ...

an ally of the Trojans against the Greeks 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 ...

. He was killed in his sleep by

Odysseus Odysseus ( ; grc-gre, Ὀδυσσεύς, Ὀδυσεύς, OdysseúsOdyseús, ), also known by the Latin variant Ulysses ( , ; lat, UlyssesUlixes), is a legendary Greek king of Ithaca and the hero of Homer's epic poem the ''Odyssey''. Odysse ...

and

Diomedes Diomedes (Jones, Daniel; Roach, Peter, James Hartman and Jane Setter, eds. ''Cambridge English Pronouncing Dictionary''. 17th edition. Cambridge UP, 2006.) or Diomede (; grc-gre, Διομήδης, Diomēdēs, "god-like cunning" or "advised by ...

who attacked the Thracian camp in the dead of night. The official naming citation was published by 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 ...

on 8 December 1998 ().

Physical characteristics

In the SDSS-based taxonomy, ''Rhesus'' is a dark

, the most common type among the Jupiter trojans. It has also been classified as a D-type by

Pan-STARRS The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1; List of observatory codes, obs. code: IAU code#F51, F51 and Pan-STARRS2 obs. code: IAU code#F52, F52) located at Haleakala Observatory, Hawaii, US, consists of astronomical c ...

' survey.

Rotation period

In August 2012, and September 2013, two rotational

lightcurve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

s of ''Rhesus'' were obtained from photometric observations in the R-band by astronomers at the

Palomar Transient Factory The Palomar Transient Factory (PTF, obs. code: I41), was an astronomical survey using a wide-field survey camera designed to search for optical transient and variable sources such as variable stars, supernovae, asteroids and comets. The projec ...

in California. Lightcurve analysis gave a

of and hours with a brightness amplitude of 0.27 and 0.24

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

, respectively ().

Diameter and albedo

According to the survey carried out by the

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 2011, ...

mission of NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 2011, ...

, ''Rhesus'' measures 42.31 kilometers in diameter and its surface has an

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 0.062, while the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for a

carbonaceous asteroid C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

of 0.057 and calculates a shorter diameter of 34.85 kilometers based on 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 11.02.

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Minor Planet Center * * {{DEFAULTSORT:Rhesus 009142 Discoveries by Cornelis Johannes van Houten Discoveries by Ingrid van Houten-Groeneveld Discoveries by Tom Gehrels 5191 Named minor planets 19771016