6395 Hilliard, provisional designation , is a stony Nysian asteroid from the inner regions of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, c ...

, approximately 4.5 kilometers in diameter. It was discovered on 21 October 1990, by Japanese astronomers

Yoshio Kushida is a Japanese seismologist, amateur astronomer and a discoverer of minor planets and comets. Kushida is the founder of the Yatsugatake South Base Observatory. He is credited by the Minor Planet Center with the discovery of 56 numbered minor pla ...

and Osamu Muramatsu at Yatsugatake South Base Observatory, Japan. The asteroid was later named after the British philanthropic couple Elizabeth and Leslie Hilliard, donors of the Herschel Museum of Astronomy.

Orbit and classification

''Hilliard'' is a stony member of the

Nysa family The Nysa family (adj. ''Nysian''; FIN: 405) is part of the Nysa–Polana complex, the largest cluster of asteroid families in the asteroid belt. It is located in the inner region of the asteroid belt, orbiting the Sun between 2.41 and 2.5 A ...

, a relatively small

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 ...

named after its namesake 44 Nysa. It orbits the Sun in the inner main-belt at a distance of 1.9–2.9 AU once every 3 years and 9 months (1,369 days). 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 0.20 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 1 ° 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 asteroid was first found on a precovery image taken at Palomar Observatory in 1949. Its first used observations was taken at Crimea-Nauchnij in 1975, when it was identified as , extending 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 ...

by 15 years prior to its official discovery observation at Yatsugatake.

Physical characteristics

Pan-STARRS The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1; obs. code: F51 and Pan-STARRS2 obs. code: F52) located at Haleakala Observatory, Hawaii, US, consists of astronomical cameras, telescopes and a computing facility that is ...

photometric survey has characterized ''Hilliard'' as a common stony

S-type asteroid S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the secon ...

. According to the survey carried out by 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 ...

with its subsequent

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, ''Hilliard'' measures 4.082 kilometers in diameter and its surface has a high

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 ...

of 0.351, while the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for stony asteroids of 0.20 and calculates a large diameter of 4.71 kilometers with 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 14.0, as diameter and albedo (reflectivity) are inversely related to each other.

Lightcurve

No 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 ''Hilliard'' has been obtained from photometric observations. In 2006, observations at the RHIT in Terre Haute, Indiana, United States, rendered no observable brightness variation. As of 2017, the body's rotation period and shape remain unknown.

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 named in honor of Elizabeth (1903–2001) and Leslie Hilliard (1905–1997), donors of the Herschel Museum of Astronomy in Bath, England. The museum was formerly the home of astronomer

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline ...

, from the garden of which he discovered the planet

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...

in 1781. The official naming citation was published on 9 September 1995 ().

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:Hilliard 006395 Discoveries by Yoshio Kushida Discoveries by Osamu Muramatsu Named minor planets 19901021