1389 Onnie, provisional designation , is a stony Koronian

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

from the outer region of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

, approximately 13 kilometers in diameter. It was discovered on 28 September 1935, by Dutch astronomer

Hendrik van Gent Hendrik van Gent (14 September 1899, Pernis – March 29, 1947, Amsterdam)''Album studiosorum Academiæ lugduno-batavæ MDCCCLXXV-MCMXXV'', A. W. Sijthoff, 1925, p. 376 was a Dutch astronomer. He moved to South Africa in 1928 in order to o ...

at Leiden Southern Station, annex to the

Johannesburg Observatory Union Observatory, also known as Transvaal Observatory, Republic Observatory and Johannesburg Observatory ( 078), is a defunct astronomical observatory in Johannesburg, South Africa that operated from 1903 to 1971. It is located on Observatory R ...

in South Africa.

Orbit and classification

The stony S-type asteroid belongs to the

Koronis family ] The Koronis or Koronian family (), also known as the Lacrimosa family, is a very large asteroid family of S-type asteroid, stony asteroids, located in the Kirkwood gap, outer region of the asteroid belt. They are thought to have been formed at l ...

, a group consisting of few hundred known bodies with nearly ecliptic, ecliptical orbits. ''Onnie'' orbits the Sun at a distance of 2.8–2.9 AU once every 4 years and 10 months (1,771 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 0.02 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 2 ° with respect to the ecliptic. As no

precoveries In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of a celestial object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This ha ...

were taken, and no prior identifications were made, 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 Johannesburg.

Lightcurve

American astronomer

Richard P. Binzel Richard "Rick" P. Binzel (born 1958) is an American astronomer and professor of planetary sciences at the Massachusetts Institute of Technology (MIT). He is a discoverer of minor planets, photometrist and the inventor of the Torino Scale, a metho ...

obtained a rotational

light-curve In astronomy, a light curve is a graph of the 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 par ...

of ''Onnie'' from photometric observations in September 1983. It gave a longer-than average

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

of 22.5 hours with a change in brightness of 0.34

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 2011 and 2013, respectively, a modeled light-curve using data from the Uppsala Asteroid Photometric Catalogue and other sources gave a period 23.0447 hours, as well as a spin axis of (183.0°, -75.0°) in

ecliptic coordinates In astronomy, the ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small So ...

().

Diameter and albedo

According to the 2014-published result by NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, List of observatory codes, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy Space observatory, space telescope in the Explorers Program launched in December 2009.. . WISE L ...

with its subsequent

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy space telescope in the Explorers Program launched in December 2009.. . WISE discovered thousands of minor planets and nu ...

mission, ''Onnie'' measures 13.77 kilometers in diameter, and its surface has an

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

of 0.198. The ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for stony Koronian asteroids of 0.24 and derives a diameter of 12.46 kilometers based on an absolute magnitude of 11.69.

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 for A. Kruyt, sister-in-law of astronomer G. Pels (1893–1966). Pels, who proposed the minor planet's name, was as a lifelong member of the

Leiden Observatory Leiden Observatory () is an astronomical institute of Leiden University, in the Netherlands. Established in 1633 to house the quadrant of Willebrord Snellius, it is the oldest operating university observatory in the world, with the only older sti ...

's staff, observer of minor planets at Leiden, as well as an orbit computer for many of Hendrik van Gent's made discoveries. The minor planet

1667 Pels Events January–March * January 11 – Aurangzeb, monarch of the Mughal Empire, orders the removal of Rao Karan Singh as Maharaja of the Bikaner State (part of the modern-day Rajasthan state of India) because of Karan's derelic ...

was named in his honour.

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:Onnie 001389 Discoveries by Hendrik van Gent Named minor planets 19350928