617 Patroclus

617 Patroclus and Menoetius
Discovery A
Discoverer	August Kopff
Discovery date	October 17, 1906
Alternate designations B	1906 VY; 1941 XC; 1962 NB
Category	Jupiter Trojan
Orbital elements C
Epoch ???
Eccentricity (e)	0.138
Semi-major axis (a)	5.228 AU
Perihelion (q)	4.506 AU
Aphelion (Q)	5.950 AU
Orbital period (P)	4365.7 d (11.95 a)
Mean orbital speed	???
Inclination (i)	22.03°
Longitude of the ascending node (Ω)	44.37°
Argument of perihelion (ω)	307.81°
Mean anomaly (M)	149.94°
Physical characteristics D
Dimensions	122 km and 112 km
Mass	1.36×1018 kg
Density	0.8 g/cm³
Surface gravity	???
Escape velocity	???
Rotation period	>4.283±0.004 days
Spectral class	P-type
Absolute magnitude	8.19
Albedo	0.047
Mean surface temperature	110 K

617 Patroclus is a binary minor planet made up of two similarly-sized objects orbiting their common centre of gravity. It is classified as a Trojan, sharing an orbit with Jupiter. It was discovered in 1907 by August Kopff, and was the second Trojan asteroid to be discovered. Recent evidence suggests that the objects are icy comets, rather than rocky asteroids. August Kopff (February 5, 1882 – April 25, 1960) was a German astronomer who discovered several comets and asteroids. ... October 17 is the 290th (in leap years the 291st) day of the year according to the Gregorian calendar. ... 1906 (MCMVI) was a common year starting on Monday (see link for calendar). ... The provisional designation of comets and asteroids are similar to each other: they both follow a pattern set in 1925 by the Minor Planet Center of the IAU. Historical designations At first, astronomers strove to assign symbols to the minor planets: 1 Ceres a stylized sickle 2 Pallas a lozenge... Minor planets, or planetoids are minor bodies of the Solar system orbiting the Sun (or of other planetary systems orbiting other stars) that are larger than meteoroids (the largest of which might be taken to be around 10 meters or so across) but smaller than major planets (Mercury having a... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... The astronomical unit (AU or au or a. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... A day (symbol: d) is a unit of time equal to 24 hours. ... In astronomy, a Julian year is a unit of time defined as exactly 365. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... Inclination in general is the angle between a reference plane and another plane or axis of direction. ... A degree (in full, a degree of arc, arc degree, or arcdegree), usually symbolized °, is a measurement of plane angle, representing 1／360 of a full rotation. ... The Longitude of the ascending node () is one of the orbital elements used to specify the orbit of an object in space. ... The argument of the perihelion is one of the orbital elements describing the orbit of a planet. ... In the study of orbital dynamics the mean anomaly is a measure of time, specific to the orbiting body p, which is a multiple of 2π radians at and only at periapsis. ... For the majority of numbered asteroids, almost nothing is known apart from a few physical parameters. ... Mass is a property of a physical object that quantifies the amount of matter it contains. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... A cubic centimetre (cm3) is an SI derived unit of volume, equal to the volume of a cube with side length of 1 centi metre. ... Gravity is a force of attraction that acts between bodies that have mass. ... In physics, for a given gravitational field and a given position, the escape velocity is the minimum speed an object without propulsion, at that position, needs to have to move away indefinitely from the source of the field, as opposed to falling back or staying in an orbit within a... In astronomy, a rotation period is the time an astronomical object takes to complete one revolution around its rotation axis. ... Asteroids are assigned a type based on spectral shape, color, and sometimes albedo. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us. ... Albedo is the measure of reflectivity of a surface or body. ... Temperature is also the name of a song by Sean Paul. ... The term binary asteroid refers to a system in which two asteroids orbit their common centre of gravity, in analogy with binary stars. ... Minor planets, or planetoids are minor bodies of the Solar system orbiting the Sun (or of other planetary systems orbiting other stars) that are larger than meteoroids (the largest of which might be taken to be around 10 meters or so across) but smaller than major planets (Mercury having a... In physics, the center of gravity (CoG) of an object is the average location of its weight. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ... Adjective Jovian Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... 1907 (MCMVII) was a common year starting on Tuesday (see link for calendar) of the Gregorian calendar (or a common year starting on Wednesday of the 13-day-slower Julian calendar). ... August Kopff (February 5, 1882 – April 25, 1960) was a German astronomer who discovered several comets and asteroids. ... Comet Hale-Bopp For other uses, see Comet (disambiguation). ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ...

Orbit

Patroclus orbits in Jupiter's trailing Lagrangian point, L₅, in an orbit called the 'Trojan node' after one of the sides in the legendary Trojan War (the other node is called the 'Greek node'). Patroclus is the only object in the Trojan camp to be named after a Greek character; the naming conventions for the Trojan asteroids were not adopted until after Patroclus was named (similarly, the asteroid Hektor is the only Trojan character to appear in the Greek camp). A contour plot of the effective potential of a two-body system (the Sun and Earth here), showing the 5 Lagrange points. ... The Trojan War was a war waged, according to legend, against the city of Troy in Asia Minor by the armies of the Achaeans, following the kidnapping (or elopement) of Helen of Sparta by Paris of Troy. ... This is a list of Trojan asteroids - asteroids that lie in elongated, curved regions around the two Lagrangian points 60° ahead and behind of Jupiter. ... A cup depicting Achilles bandaging Patroklos arm, by Sosias. ... 624 Hektor is the largest of the Jovian Trojan asteroids. ... This is a list of Trojan asteroids - asteroids that lie in elongated, curved regions around the two Lagrangian points 60° ahead and behind of Jupiter. ...

Binary

In 2001, it was discovered that Patroclus is a binary object, made up of two components of roughly similar size. In February, 2006, a team of astronomers led by Franck Marchis measured accurately the orbit of the system using the Keck Laser Guide Star Adaptive Optics system. They estimated^[1] that the two components orbit around their center of mass in 4.283±0.004 d at a distance of 680±20 km, describing a roughly circular orbit. Combining their observations with thermal measurements taken in November, 2000 the team estimated the size of the components of the system. The slightly larger component, which measures 122 km in diameter, retains the name Patroclus. The smaller component, measuring 112 km, is now named Menoetius (full name (617) Patroclus I Menoetius), after the legendary Patroclus's father. Its provisional designation was S/2001 (617) 1. 2001: A Space Odyssey. ... The term binary asteroid refers to a system in which two asteroids orbit their common centre of gravity, in analogy with binary stars. ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... The W. M. Keck Observatory is home to the two largest optical/near-infrared telescopes at the 4,145 meter (13,600 ft) summit of Mauna Kea in Hawaii. ... It has been suggested that this article or section be merged with Center of gravity. ... A day (symbol: d) is a unit of time equal to 24 hours. ... This article is about the year 2000. ... The provisional designation of comets and asteroids are similar to each other: they both follow a pattern set in 1925 by the Minor Planet Center of the IAU. Historical designations At first, astronomers strove to assign symbols to the minor planets: 1 Ceres a stylized sickle 2 Pallas a lozenge...

Composition

Because of the density of the components (0.8 g/cm³) is less than water and about one third that of rock, the Keck team of researchers suggest that the Patroclus system, previously thought to be a pair of rocky asteroids, is more similar to a comet in composition. It is suspected that many Trojan asteroids are in fact small planetesimals captured in the Lagrange point of Jupiter-Sun system during the outer migration of the giant planets, 3.9 billion years ago. This scenario was proposed by A. Morbidelli and in colleagues in a series of articles published in May, 2005 in Nature journal. An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Comet Hale-Bopp For other uses, see Comet (disambiguation). ... ÈàÌàìòòIn cosmogony, planetesimals are objects thought to exist within solar nebulae. ... A gas giant is a large planet that is not composed mostly of rock or other solid matter. ... Template:Diffgggtgerent calendars 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... First title page, November 4, 1869 Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ...

Notes

1. ↑  UC-Berkeley press release on cometary origin

External links

• Johnston's Archive: detailed orbital and physical data
• Keck Obs. press release Trojan Asteroid Patroclus: Comet in Disguise?
• Patroclus and Menoetius web page

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