1208 Troilus is a large and notably inclined
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 31 December 1931, by German astronomer
Karl Reinmuth
Karl Wilhelm Reinmuth (4 April 1892 in Heidelberg – 6 May 1979 in Heidelberg) was a German astronomer and a prolific discoverer of 395 minor planets.
Scientific career
From 1912 to 1957, Reinmuth was working as an astronomer at the Lande ...
at the
Heidelberg Observatory
Heidelberg (; Palatine German: ') is a city in the German state of Baden-Württemberg, situated on the river Neckar in south-west Germany. As of the 2016 census, its population was 159,914, of which roughly a quarter consisted of student ...
in southern Germany.
The unusual
F-type asteroid
F-type asteroids are a relatively uncommon type of carbonaceous asteroid, falling into the wider C-group.
Characteristics
F-type asteroids have spectra generally similar to those of the B-type asteroids, but
lack the "water" absorption feature ar ...
belongs to the
largest Jupiter trojans and has a long
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 56.2 hours.
It was named after the Trojan prince
Troilus
Troilus ( or ; grc, Τρωΐλος, Troïlos; la, Troilus) is a legendary character associated with the story of the Trojan War. The first surviving reference to him is in Homer's ''Iliad,'' composed in the late 8th century BCE.
In Greek myth ...
, who was killed by
Achilles
In Greek mythology, Achilles ( ) or Achilleus ( grc-gre, Ἀχιλλεύς) was a hero of the Trojan War, the greatest of all the Greek warriors, and the central character of Homer's ''Iliad''. He was the son of the Nereid Thetis and Peleus, k ...
.
Orbit and classification
''Troilus'' 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.
...
orbiting in the trailing
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 ...
at Jupiter'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 in a
1:1 resonance . It is also a non-
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
asteroid of the
Jovian background population.
It orbits the Sun at a distance of 4.8–5.7
AU once every 12 years (4,395 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 5.25 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 0.09 and a high
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 34
° 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 ...
.
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 Heidelberg in December 1931.
Physical characteristics
In the
Tholen classification
An asteroid spectral type is assigned to asteroids based on their emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiated ...
, ''Troilus'' has an ambiguous and unusual spectrum, closest to that of an
F-type and somewhat similar to a common
C-type 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 ...
(FCU).
It has also been characterized as a carbonaceous C-type in the Barucci taxonomy (C0-type).
Rotation period
In April 2007, a 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 ...
of ''Troilus'' was obtained from
photometric observations by
Lawrence Molnar at the
Calvin-Rehoboth Robotic Observatory in New Mexico. Lightcurve analysis gave 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 hours with a brightness variation of
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 ...
().
While not being a slow rotator, ''Troilus'' has a significantly longer period than most asteroids, and one of longest of all larger Jupiter trojans.
The period also supersedes previous observations made by Linda French with the
0.9-meter SMARTS telescope at
Cerro Tololo in the 1980s and by Federico Manzini at the Sozzago Astronomical Station , which gave a period of 24 and 63.8 hours, respectively ().
Diameter and albedo
According to the surveys carried out by the Infrared Astronomical Satellite
IRAS
The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...
, the Japanese
Akari satellite and 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, ...
, ''Troilus'' measures between 100.48 and 111.36 kilometers in diameter and its surface has an
albedo
Albedo (; ) is the measure of the diffuse reflection of 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 that refl ...
between 0.037 and 0.0419.
The ''Collaborative Asteroid Lightcurve Link'' derives an albedo of 0.0397 and a diameter of 103.31 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 9.05.
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 the young Trojan prince
Troilus
Troilus ( or ; grc, Τρωΐλος, Troïlos; la, Troilus) is a legendary character associated with the story of the Trojan War. The first surviving reference to him is in Homer's ''Iliad,'' composed in the late 8th century BCE.
In Greek myth ...
, the son of King
Priam ''(also see
884 Priamus
884 Priamus is a large Jupiter trojan from the Trojan camp, approximately in diameter. It was discovered on 22 September 1917, by German astronomer Max Wolf at Heidelberg Observatory in southern Germany. The dark D-type asteroid is one of the ...
)'', who in a medieval legend loved Cressida ''(see
548 Kressida)'' and lost her to Diomedes ''(see
1437 Diomedes)''. Troilus was killed by
Achilles
In Greek mythology, Achilles ( ) or Achilleus ( grc-gre, Ἀχιλλεύς) was a hero of the Trojan War, the greatest of all the Greek warriors, and the central character of Homer's ''Iliad''. He was the son of the Nereid Thetis and Peleus, k ...
''(see
588 Achilles
Achilles ( minor planet designation: 588 Achilles) is a large Jupiter trojan asteroid of the Greek camp. Achilles was the first Jupiter trojan to be discovered, and was discovered by Max Wolf at the Heidelberg Observatory in 1906. Wolf named the ...
)'' 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 ...
. The official naming citation was published by
Paul Herget
Paul Herget (January 30, 1908 – August 27, 1981) was an American astronomer and director of the Cincinnati Observatory, who established the Minor Planet Center after World War II.
Career
Herget taught astronomy at the University of Cincinna ...
in ''
The Names of the Minor Planets
Paul Herget (January 30, 1908 – August 27, 1981) was an American astronomer and director of the Cincinnati Observatory, who established the Minor Planet Center after World War II.
Career
Herget taught astronomy at the University of Cincinna ...
'' in 1955 ().
References
External links
Asteroid Lightcurve Database (LCDB) query form
)
Dictionary of Minor Planet Names Google books
– Observatoire de Genève, Raoul Behrend
– Minor Planet Center
*
*
{{DEFAULTSORT:Troilus
001208
Discoveries by Karl Wilhelm Reinmuth
Named minor planets
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