2594 Acamas is a mid-sized

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 on 4 October 1978, by American astronomer

Charles Kowal Charles Thomas Kowal (November 8, 1940 – November 28, 2011) was an American astronomer known for his observations and discoveries in the Solar System. As a staff astronomer at Caltech's Mount Wilson and Palomar Mountain observatories between ...

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 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. ...

has a longer-than average

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 26 hours and possibly an elongated shape. It was named after the Thracian leader Acamas from Greek mythology.

Orbit and classification

''Acamas'' is a dark Jovian

in a 1:1 orbital resonance 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 on its orbit . It is also a non- family asteroid of the Jovian background population. It orbits the Sun at a distance of 4.6–5.5 AU once every 11 years and 5 months (4,159 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 5.06 AU). Its orbit has an eccentricity of 0.08 and an inclination of 6 ° with respect to the ecliptic. The body's observation arc begins with 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 September 1953, or 25 years prior to its official discovery observation.

Physical characteristics

''Acamas'' is an assumed, carbonaceous C-type asteroid, while most larger Jupiter trojans are

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 ...

Rotation period

In September 2013, a rotational lightcurve of ''Acamas'' was 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 hours with a brightness amplitude of 0.50 magnitude (). A high brightness variation typically indicates that the body has an elongated rather than spherical shape.

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, ''Acamas'' measures 25.87 kilometers in diameter and its surface has an albedo 0.06, while the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 19.21 kilometers based on an absolute magnitude of 12.31.

Naming

This minor planet was named by

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

's ''Minor Planet Names Committee'' from Greek mythology after the warrior Acamas (son of Eussorus), ally of Troy and leader of the Thracian contingent during the Trojan War. He was killed by Ajax. The name was suggested by Frederick Pilcher and 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 6 February 1993 ().

Orbit and classification

Physical characteristics

Rotation period

Diameter and albedo

Naming

References

External links