1647 Menelaus 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 (celestial body), trojan Libration point orbit, librat ...

from the

Greek camp This is a list of Jupiter trojans that lie in the Greek camp, an elongated curved region around the leading Lagrangian point (), 60 ° ahead of Jupiter in its orbit. All the asteroids at Jupiter's point have names corresponding to participants ...

, approximately in diameter. It was discovered on 23 June 1957 by American astronomer

Seth Nicholson Seth Barnes Nicholson (November 12, 1891 – July 2, 1963) was an American astronomer. He worked at the Lick observatory in California, and is known for discovering several moons of Jupiter in the 20th century. Nicholson was born in Springfield, ...

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 and later named after the Spartan King

Menelaus In Greek mythology, Menelaus (; ) was a Greek king of Mycenaean (pre- Dorian) Sparta. According to the ''Iliad'', the Trojan war began as a result of Menelaus's wife, Helen, fleeing to Troy with the Trojan prince Paris. Menelaus was a central ...

from Greek mythology. The dark

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 ...

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 17.7 hours. It is the principal body of the proposed Menelaus cluster, which encompasses several, mostly tentative Jovian

asteroid families An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An a ...

Orbit and classification

''Menelaus'' is a dark Jovian

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 relation ...

with Jupiter. It is located in the leading

at the Gas Giant's

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 ° ahead of its orbit . Since the discovery of the first Jupiter trojan, 588 Achilles, by astronomer

Max Wolf Maximilian Franz Joseph Cornelius Wolf (21 June 1863 – 3 October 1932) was a German astronomer and a pioneer in the field of astrophotography. He was the chairman of astronomy at the University of Heidelberg and director of the Heidelberg-K� ...

in 1906, more than 7000 Jovian asteroids have already been discovered. It orbits the Sun at a distance of 5.1–5.3 AU once every 11 years and 11 months (4,347 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 5.21 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 0.02 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 6 ° concerning 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 ...

. ''Menelaus'' was first imaged at Palomar in November 1951. This

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

extends 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 ...

by more than 5 years before its official discovery observation.

Menelaus cluster

In 1993, Andrea Milani suggested that ''Menelaus'' might be the

parent body A parent body in meteoritics is the celestial body from which originates a meteorite or a class of meteorites. Identification It is easiest to correlate a meteorite with a parent body when the parent body still exists. This is the case for Lun ...

of an

asteroid family An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An ...

based on a modified HCM-analysis. The finding was also mentioned by

David Jewitt David Clifford Jewitt (born 1958) is a British-American astronomer who studies the Solar System, especially its minor bodies. He is based at the University of California, Los Angeles, where he is a Member of the Institute for Geophysics and Pla ...

in 2004, who noted that the Menelaus family is the largest proposed dynamic family to exist among the Jupiter trojans, despite having only eight members. In 2008,

Fernando Roig Fernando Roig Alfonso (born 25 June 1947) is a Spanish billionaire businessman, the owner and president of the Spanish football club Villarreal CF, Villarreal, owner and president of Spanish ceramic company Pamesa and owner of 9% of the Spanish ...

and Ricardo Gil-Hutton described this particular aggregation of Jupiter trojans as the "Menelaus clan," which, similar to the

Flora family The Flora family (''adj. Florian''; ; also known as the Ariadne family) is a prominent family of stony asteroids located in the inner region of the asteroid belt. It is one of the largest families with more than 13,000 known members, or approx ...

in the inner asteroid belt, is composed of several families (or subfamilies). In this publication, the Menelaus clan encompasses a dozen clusters if the separation criteria used in the HCM analysis are sufficiently relaxed. The principal bodies of these proposed family-like clusters include: 1647 Menelaus,

3548 Eurybates 3548 Eurybates ( ) is a carbonaceous Jupiter trojan from the Greek camp and the parent body of the Eurybates family, approximately in diameter. It is a target to be visited by the ''Lucy'' mission in August 2027. Discovered during the second ...

, 1749 Telamon, 12973 Melanthios, 13062 Podarkes, 5436 Eumelos, 2148 Epeios, 4007 Euryalos, 4138 Kalchas, 3063 Makhaon and others. Except for the Eurybates family, which was studied in more detail by Jakub Rozehnal and Miroslav Brož in 2011 ''(also see )'', all other proposed families with their principal bodies in the Menelaus clan, including ''Menelaus'' itself, are tentative and not listed neither on the Asteroids—Dynamic Site (Milani and Knežević) nor included in the robust HCM-analysis by Nesvorný ''(also see )''. Instead, these bodies are considered 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 ...

asteroids of the Jovian background population.

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 after the Greek mythological figure,

, husband of

Helen of Troy Helen (), also known as Helen of Troy, or Helen of Sparta, and in Latin as Helena, was a figure in Greek mythology said to have been the most beautiful woman in the world. She was believed to have been the daughter of Zeus and Leda (mythology), ...

, brother of

Agamemnon In Greek mythology, Agamemnon (; ''Agamémnōn'') was a king of Mycenae who commanded the Achaeans (Homer), Achaeans during the Trojan War. He was the son (or grandson) of King Atreus and Queen Aerope, the brother of Menelaus, the husband of C ...

, and king and leader of the

Sparta Sparta was a prominent city-state in Laconia in ancient Greece. In antiquity, the city-state was known as Lacedaemon (), while the name Sparta referred to its main settlement in the Evrotas Valley, valley of Evrotas (river), Evrotas rive ...

n contingent of the Greek army during the

Trojan War The Trojan War was a legendary conflict in Greek mythology that took place around the twelfth or thirteenth century BC. The war was waged by the Achaeans (Homer), Achaeans (Ancient Greece, Greeks) against the city of Troy after Paris (mytho ...

. The discoverer followed the convention to name bodies located in the camp to the east of Jupiter after famous Greek heroes. The ''Dictionary of Minor Planet Names'' also mentions that the lunar crater ''Menelaus'' was named after the Greek hero. However, based on the official International Astronomical Union– WGPSN nomenclature, it is named after Greek geometer and astronomer

Menelaus of Alexandria Menelaus of Alexandria (; , ''Menelaos ho Alexandreus''; c. 70 – 140 CE) was a Greek mathematician and astronomer, the first to recognize geodesics on a curved surface as natural analogs of straight lines. Life and works Although very li ...

(70–140). The official 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 ...

in June 1960 ().

Physical characteristics

''Menelaus'' is an assumed C-type, while most larger Jupiter trojans are

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 ...

s. It has a V–I color index of 0.866.

Rotation period

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 obtained a rotational

light curve 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 ''Menelaus'' from photometric observation in the R-band in October 2010. It gave a

of 17.7390 hours with a brightness variation of 0.32

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 ...

in the R-band (). In February 2014, a refined period of hours with an amplitude of 0.15 magnitude was determined by American astronomer Robert D. Stephens at the

Center for Solar System Studies This is a list of observatory codes (IAU codes or MPC codes) 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 Astronomi ...

().

Diameter and albedo

According to the survey by 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 ...

with its subsequent

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, ''Menelaus'' measures 42.72 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 0.056. The ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 44.22 kilometers using an absolute magnitude of 10.5.

Orbit and classification

Menelaus cluster

Naming

Physical characteristics

Rotation period

Diameter and albedo

Notes

References

External links