5258 Rhoeo, ''provisional designation'': , 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 Eurybates family 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 1 January 1989, by Japanese astronomer

Yoshiaki Oshima (born 1952) is a Japanese astronomer at Gekko Observatory and prolific discoverer of 61 asteroids as credited by the Minor Planet Center, and include the binary asteroid 4383 Suruga, the potentially hazardous object (7753) 1988 XB and the Jupit ...

at the Gekko Observatory, east of Shizuoka, Japan. The assumed

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 ...

belongs to the 90 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 19.9 hours. It was named from Greek mythology after

Rhoeo In Greek mythology, Rhoeo (; grc, Ῥοιώ ''Rhoiṓ'') was the daughter of Staphylus and Chrysothemis, sister to Parthenos and Molpadia or Hemithea. Mythology Parthenius relates that she once experienced a great jealousy of her sister Hemi ...

, lover of Apollo and mother of his son

Anius In Greek mythology, Anius (Ancient Greek: Ἄνιος) was a king of Delos and priest of Apollo. Family He was the son of Apollo and Rhoeo, daughter of Staphylus and Chrysothemis. Mythology Anius was born either on the island of Delos, which ...

Orbit and classification

''Rhoeo'' 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 leading Greek camp 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 ° ahead of the Gas Giant's orbit in a 1:1 resonance ''(see

Trojans in astronomy In astronomy, a trojan is a small celestial body (mostly asteroids) that shares the orbit of a larger body, remaining in a stable orbit approximately 60° ahead of or behind the main body near one of its Lagrangian points and . Trojans can sha ...

)''. It orbits the Sun at a distance of 4.8–5.6 AU once every 11 years and 9 months (4,303 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 5.18 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-center, in geometry * Eccentricity (graph theory) of a v ...

of 0.08 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 6 ° 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 Gekko Observatory in January 1989.

Eurybates family

''Rhoeo'' is the member of the small Eurybates family (), named after its parent body, 3548 Eurybates. This

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 a ...

comprises 218 known members of carbonaceous and/or primitive composition, and is one of only a few families identified among the Jovian asteroids; with four of them in the Greek camp. This potentially collisional family was first characterized by Jakub Rozehnal and Miroslav Brož in 2011, and further described in 2014. Other members of this family include the Jupiter trojans

8060 Anius 8 (eight) is the natural number following 7 and preceding 9. In mathematics 8 is: * a composite number, its proper divisors being , , and . It is twice 4 or four times 2. * a power of two, being 2 (two cubed), and is the first number of t ...

, 9818 Eurymachos, , and 360072 Alcimedon. In the HCM analysis by Milani and Knežević, however, ''Rhoeo'' belongs to the background population.

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 ''minor ...

was numbered 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 14 July 1992 (). 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

from Greek mythology, who became the lover of Apollo and by him the mother of

. When her father discovered her pregnancy, he believed she was impregnated by a man rather than a god. He placed her in a chest and cast her out to sea. Anius later prophesied the decade-long siege of Troy.

Physical characteristics

''Rhoeo'' is an assumed, carbonaceous

. The overall

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of members of the Eurybates family is that of a C- and P-type. It has a high V–I color index of 1.01.

Rotation period

In April 2015, the so-far only

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 ...

was obtained 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. The photometric observations gave a

of hours and a brightness variation of 0.14 magnitude ().

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 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, ...

, ''Rhoeo'' measures 53.28 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 ...

of 0.052, while the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 50.77 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 10.2.

Notes

References

External links

Long-term evolution of asteroid families among Jovian Trojans
Jakub Rozehnal and Miroslav Brož (2014)
Asteroid Lightcurve Database (LCDB)
query form

)

– Minor Planet Center * * {{DEFAULTSORT:Rhoeo 005258 005258 Discoveries by Yoshiaki Oshima Named minor planets 19890101