5648 Axius, ''provisional designation'': , is a Jupiter trojan 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 11 November 1990, by Japanese amateur astronomers

Kin Endate is a Japanese amateur astronomer who has discovered hundreds of asteroids, most of them in collaboration with Kazuro Watanabe, placing him among the most prolific discoverers of minor planets. Career in astronomy Kin Endate was born in Iwa ...

and Kazuro Watanabe at the

Kitami Observatory Kitami Observatory is an astronomical observatory in the Kitami-Abashiri Region Cultural Centre in eastern Hokkaidō, Japan. Its observatory code is 400. It is 0.72344 Earth radii from the rotation axis and +0.68811 Earth radii from the equatorial ...

on the northern island of Hokkaidō, Japan. The dark

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 ...

belongs to the 70 largest Jupiter trojans and has a long rotation period of 37.6 hours. It was named after Axius, a river god from Greek mythology.

Orbit and classification

''Axius'' is a dark Jovian asteroid 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 relationsh ...

with Jupiter. It is located in the trailering

at the Gas Giant's Lagrangian point, 60 ° behind its orbit . It is also a non-

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

asteroid of the Jovian background population. It orbits the Sun at a distance of 4.3–6.0 AU once every 11 years and 8 months (4,271 days; semi-major axis of 5.15 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 0.17 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 23 ° 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 agains ...

. 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 taken at the Palomar Observatory in June 1950, more than 40 years prior to its official discovery observation.

Numbering and 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 ''mino ...

was numbered on 1 September 1993 (). On 14 May 2021, the object was named by the

Working Group Small Body Nomenclature In ancient times, only the Sun and Moon, a few stars, and the most easily visible planets had names. Over the last few hundred years, the number of identified astronomical objects has risen from hundreds to over a billion, and more are discovered e ...

(WGSBN), after Axius, a river god from Greek mythology, who is the son of Oceanus and Tethys, the father of Pelegon and grandfather of

Asteropaios In the ''Iliad'', Asteropaios (; Greek: Ἀστεροπαῖος; Latin: ''Asteropaeus'') was a leader of the Trojan-allied Paeonians along with fellow warrior Pyraechmes. Family Asteropaios was the son of Pelagon, who was the son of the river ...

Physical characteristics

In both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), ''Axius'' is a dark

, the dominant

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

among the larger Jupiter trojans. It has a typical V–I color index of 0.90.

Rotation period

In February 2005, Federico Manzini at the Sozzago Astronomical Station in Italy obtained the first 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 freq ...

of ''Axius''. It gave a tentative rotation period of 16.04 hours with a brightness amplitude of 0.22 based on three nights of observation

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 June 2006, photometric observations over eight nights were made by Italian astronomer

Stefano Mottola This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 numb ...

at the Calar Alto Observatory in Spain. Lightcurve analysis gave a rotation period of hours with a brightness amplitude of 0.20

(), superseding Manzini's previous result. A concurring period of 37.6083 hours with an amplitude of 0.19 magnitude was measured by astronomers at the Palomar Transient Factory in October 2013 (). While not being a slow rotator, its period is significantly longer than that of most larger Jupiter trojans ''(see list below)''.

Diameter and albedo

According to the survey carried out by 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 201 ...

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 201 ...

, ''Axius'' measures 59.30 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 ...

0.073, while the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for a

carbonaceous Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up ...

asteroid of 0.057 and calculates a diameter of 63.91 kilometers based on an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it ...

of 9.7. A diameter measurement for this asteroid has not been previously published by

Akari Akari (ASTRO-F) was an infrared astronomy satellite developed by Japan Aerospace Exploration Agency, in cooperation with institutes of Europe and Korea. It was launched on 21 February 2006, at 21:28 UTC (06:28, 22 February JST) by M-V rocke ...

and

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 ...

Notes

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)

– Minor Planet Center * * {{DEFAULTSORT:Axius 005648 Discoveries by Kin Endate Discoveries by Kazuro Watanabe Minor planets named from Greek mythology Named minor planets 19901111