17492 Hippasos (

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

) 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 librates around one of Jupiter's stable Lagrange poin ...

and member of the Ennomos family 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 10 December 1991, by astronomer

Freimut Börngen Freimut Börngen (; 17 October 1930 – 19 June 2021) was a German astronomer and a prolific discoverer of minor planets. A few sources give his first name wrongly as "Freimuth". The Minor Planet Center credits him as F. Borngen. He studied ga ...

at the Karl Schwarzschild Observatory in Tautenburg, Germany. The 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. ...

belongs to the 80 largest Jupiter trojans and has 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 17.8 hours. It was named after the Trojan prince Hippasus (Hippasos) from Greek mythology.

Orbit and classification

Hippasos is a Jovian

in the so-called

, located in the

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 Jupiter, orbiting in a 1:1 resonance with the Gas Giant . It orbits the Sun at a distance of 4.8–5.5 AU once every 11 years and 8 months (4,262 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 5.14 AU). Its orbit has an eccentricity of 0.07 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 Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 29 ° with respect to the ecliptic. 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 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 ...

published by the

Digitized Sky Survey The Digitized Sky Survey (DSS) is a digitized version of several photographic astronomical surveys of the night sky, produced by the Space Telescope Science Institute between 1983 and 2006. Versions and source material The term Digitized Sky S ...

and taken at the

Siding Spring Observatory Siding Spring Observatory near Coonabarabran, New South Wales, Australia, part of the Research School of Astronomy & Astrophysics (RSAA) at the Australian National University (ANU), incorporates the Anglo-Australian Telescope along with a coll ...

in September 1977, more than 14 years prior to its official discovery observation at Tautenburg.

Asteroid family

Hippasos is a member of the Ennomos family (), one of few known Jovian

asteroid families An asteroid is a minor planet of the Solar System#Inner solar system, 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 o ...

, named after

4709 Ennomos 4709 Ennomos is a large Jupiter trojan from the Trojan camp and the namesake of the small Ennomos family, approximately in diameter. It was discovered on 12 October 1988, by American astronomer Carolyn Shoemaker at the Palomar Observatory in C ...

''(see also )''. A different HCM analysis finds this asteroid to be the

parent body In meteoritics, a parent body is the celestial body from which originates a meteorite or a class of meteorites. Identification The easiest way to correlate a meteorite with a parent body is when the parent body still exists. This is the case fo ...

of its own Hippasos family, first described by Jakub Rozehnal and Miroslav Brož in 2014. According to the astronomers' model, the Hippasos family consists of 104 known members, and was formed 1 to 2 billion years ago. The extrapolated size of the original body is between 67 and 168 kilometers, which is strongly influenced by the amount of possible

interloper Interloper, Interlopers or The Interlopers may refer to: Entertainment * '' The Interloper: Lee Harvey Oswald Inside the Soviet Union'', a 2013 book by Peter Savodnik * Interloper (comics), a fictional character in the Marvel Comics universe * I ...

s into the family.

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 Trojan prince Hippasus (Hippasos). The son of King

Priam In Greek mythology, Priam (; grc-gre, Πρίαμος, ) 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 Mo ...

supported

Aeneas In Greco-Roman mythology, Aeneas (, ; from ) was a Trojan hero, the son of the Trojan prince Anchises and the Greek goddess Aphrodite (equivalent to the Roman Venus). His father was a first cousin of King Priam of Troy (both being grandsons ...

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 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 9 March 2001 ().

Physical characteristics

Hippasos is an assumed 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 December 2013, a rotational lightcurve of Hippasos was obtained from photometric observations by

Robert Stephens Sir Robert Graham Stephens (14 July 193112 November 1995) was a leading English actor in the early years of Britain's Royal National Theatre. He was one of the most respected actors of his generation and was at one time regarded as the natur ...

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. For a detailed description, ''see observations of small Solar System bodies''. List References * {{DEFAULTSORT:Observat ...

in Landers, California. Lightcurve analysis gave a well-defined

of hours with a brightness amplitude of 0.21 magnitude ().

Diameter and albedo

According to the survey carried out by the NEOWISE 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, ...

, Hippasos measures 53.98 kilometers in diameter and its surface has an

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, 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 ...

0.066, 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 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 10.0.

Notes

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Minor Planet Center * * {{DEFAULTSORT:Hippasos 017492 017492 Discoveries by Freimut Börngen Named minor planets 19911210