4708 Polydoros is a

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 (celestial body), trojan Libration point orbit, librat ...

from the Trojan camp, approximately in diameter. It was discovered on 11 September 1988, by American astronomer

Carolyn Shoemaker Carolyn Jean Spellmann Shoemaker (June 24, 1929 – August 13, 2021) was an American astronomer and a co-discoverer of Comet Shoemaker–Levy 9, Comet Shoemaker–Levy 9. She discovered 32 comets (then a record for the most by an individu ...

at the

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 ...

in California. The

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

belongs to the 80 largest Jupiter trojans and has a

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

of 7.5 hours. It was named after the Trojan prince

Polydorus In Greek mythology, Polydorus (; , i.e. "many-gift d) or Polydoros referred to several different people. *Polydorus, son of Phineus and Cleopatra, and brother of Polydector (Polydectus). These two sons by his first wife were blinded by Phineus be ...

, from Greek mythology.

Orbit and classification

''Polydoros'' is a Jovian

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

located in the

Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium (mechanics), equilibrium for small-mass objects under the gravity, gravitational influence of two massive orbit, orbiting b ...

, 60 ° behind on Jupiter's orbit in the so-called Trojan camp . It is also a non-

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

asteroid of the Jovian background population. It orbits the Sun at a distance of 4.9–5.6 AU once every 12 years and 1 month (4,403 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 longe ...

of 5.26 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-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.06 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 reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 7 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

. 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 official discovery observation at Palomar in September 1988.

Physical characteristics

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

. It has also been characterized 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 ...

' survey. Its V–I color index of 0.96 is typical for most larger D-type Jupiter trojans ''(see table below)''.

Rotation period

In August 2011, a rotational

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

of ''Polydoros'' was obtained from photometric observations by Linda French at the

Cerro Tololo Inter-American Observatory The Cerro Tololo Inter-American Observatory (CTIO) is an Astronomy, astronomical observatory located on the summit of Mt. Cerro Tololo in the Coquimbo Region of northern Chile, with additional facilities located on Mt. Cerro Pachón about to th ...

in Chile. Lightcurve analysis, however, gave an incorrect

of hours with a brightness variation of 0.25

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 ...

(). Several subsequent observations during 2014–2018 by Daniel Coley and Robert D. Stephens at the Center for Solar System Studies achieved a good period determination, with the best-rated one from November 2015, which gave a period of hours and an amplitude of 0.17 magnitude ().

Diameter and albedo

According to the survey carried out by the

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy space telescope in the Explorers Program launched in December 2009.. . WISE discovered thousands of minor planets and nu ...

mission of NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, List of observatory codes, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy Space observatory, space telescope in the Explorers Program launched in December 2009.. . WISE L ...

, ''Polydoros'' measures 54.96 kilometers in diameter and its surface has an

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 ...

of 0.064, while the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for a carbonaceous asteroid of 0.057, and calculates a diameter of 55.67 kilometers based on an absolute magnitude of 10.0.

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 by the discoverer from

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

after the Trojan prince

, the youngest and swiftest of King

Priam In Greek mythology, Priam (; , ) was the legendary and last king of Troy during the Trojan War. He was the son of Laomedon. His many children included notable characters such as Hector, Paris, and Cassandra. Etymology Most scholars take the e ...

's many sons. Although forbidden by his father, Polydoros confronted Achilles anyway, and was killed by him beside the River Scamander, near his brother Lycaon . 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. Funct ...

on 28 April 1991 ().

Orbit and classification

Physical characteristics

Rotation period

Diameter and albedo

Naming

Notes

References

External links