891 Gunhild ( ''prov. designation'': ''or'' ) is a large

background asteroid 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 ...

from the outer regions 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 ...

, that measures approximately in diameter. It was discovered on 17 May 1918, by astronomer

Max Wolf Maximilian Franz Joseph Cornelius Wolf (21 June 1863 – 3 October 1932) was a German astronomer and a pioneer in the field of astrophotography. He was the chairman of astronomy at the University of Heidelberg and director of the Heidelberg-K� ...

at the Heidelberg-Königstuhl State Observatory in southwest Germany. 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 ...

has a

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 11.9 hours. Any reference of the asteroid's name to a person is unknown.

Orbit and classification

''Gunhild'' is a non-

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

asteroid of the main belt's background population when applying the

hierarchical clustering method 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 ...

to its proper orbital elements. It orbits the Sun in the outer asteroid belt at a distance of 2.8–2.9 AU once every 4 years and 10 months (1,769 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 longe ...

of 2.86 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 0.03 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 14 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

. The asteroid was first observed as () at

Simeiz Observatory Simeiz Observatory (also spelled Simeis or Simeïs) was an astronomy research observatory until the mid-1950s. It is located on Mount Koshka, Crimea, by the town of Simeiz. Part of the Crimean Astrophysical Observatory, it is currently used fo ...

in November 1915. 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 at Heidelberg Observatory on 18 May 1918, the night after its official discovery observation.

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 ...

is named after a Feminine German first name. Any reference of this name to a person or occurrence is unknown.

Unknown meaning

Among the many thousands of

named minor planets Named may refer to something that has been given a name. Named may also refer to: * named (computing), a widely used DNS server * Naming (parliamentary procedure) * The Named (band), an American industrial metal group In literature: * ''The Nam ...

, ''Gunhild'' is one of 120 asteroids, for which no official naming citation has been published. All of these low-numbered asteroids have numbers between and and were discovered between 1876 and the 1930s, predominantly by astronomers

Auguste Charlois Auguste Honoré Charlois (; November 26, 1864 – March 26, 1910) was a French astronomer who discovered 99 asteroids while working at the Nice Observatory in southeastern France. Asteroid discovery His first discovery was the asteroid 267 Tirz ...

, Johann Palisa,

and

Karl Reinmuth Karl Wilhelm Reinmuth (4 April 1892 in Heidelberg – 6 May 1979 in Heidelberg) was a German astronomer and a prolific discoverer of 395 minor planets. Scientific career From 1912 to 1957, Reinmuth was working as an astronomer at the He ...

Physical characteristics

In both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), as well as in the SDSS-based taxonomy, ''Gunhild'' is a dark

. This asteroid spectral type is common among outer belt asteroids and very common among the

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 (celestial body), trojan Libration point orbit, librat ...

population.

Rotation period

In July 2015, a rotational

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

of ''Gunhild'' was obtained from photometric observations by the Spanish group of asteroid observers, OBAS. Lightcurve analysis gave a

of hours with a brightness amplitude of

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 ...

(). The result supersedes period determinations of () by Robert Stephens in 2000, () by Laurent Bernasconi in 2005, and () by Janus Kozdon in 2015 ().

Diameter and albedo

According to the survey carried out by the Infrared Astronomical Satellite

IRAS The Infrared Astronomical Satellite (Dutch language, Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a astronomical survey, survey of the entire night sky at infrared wavelengths. Launched on 25 Janu ...

, the Japanese Akari satellite, and the

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 of 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 ...

(WISE), ''Gunhild'' measures (), () and () 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 (), () and (), respectively. The ''Collaborative Asteroid Lightcurve Link'' derives an albedo of 0.0656 and a diameter of 51.89 kilometers based on an absolute magnitude of 10.0. Alternative mean-diameter measurements published by the WISE team include (), () and () with corresponding albedos of (), () and (). Several

asteroid occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks f ...

observed between 2010 and 2014 gave a best-fit ellipse dimension of 52.0 × 52.0 kilometers (one observation) and 63.0 × 63.0 kilometers (three observations). These timed observations are taken when the asteroid passes in front of a distant star.

References

External links

Lightcurve Database Query
(LCDB), at ''www.minorplanet.info''
Dictionary of Minor Planet Names
Google books

– ''Geneva Observatory'', Raoul Behrend
Discovery Circumstances: Numbered Minor Planets (1)-(5000)
– Minor Planet Center * * {{DEFAULTSORT:Gunhild 000891 Discoveries by Max Wolf Named minor planets 19180517