817 Annika ('' prov. designation:'' ''or'' ) is a background asteroid in the region of the

Eunomia family The Eunomia or Eunomian family () is a large asteroid family of S-type asteroids named after the asteroid 15 Eunomia. It is the most prominent family in the intermediate asteroid belt and the 6th-largest family with nearly six thousand known members ...

, located in the central portion of the asteroid belt. It was discovered on 6 February 1916, by German 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 Heidelberg-Königstuhl State Observatory (german: Landessternwarte Heidelberg-Königstuhl) is a historic astronomical observatory located near the summit of the Königstuhl hill in the city of Heidelberg in Germany. The predecessor of the curre ...

in southwest Germany. The stony S-type asteroid (Sl) 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 10.56 hours and measures approximately in diameter. Any reference of the asteroid's name to a person is unknown.

Orbit and classification

''Annika'' is a non- family asteroid of the main belt's background population when applying the hierarchical clustering method (HCM) to its

proper orbital elements __NOTOC__ The proper orbital elements or proper elements of an orbit are constants of motion of an object in space that remain practically unchanged over an astronomically long timescale. The term is usually used to describe the three quantitie ...

by Nesvorný as well as by Milani and

Knežević Knežević ( sr, Кнежевић) is a Serbian, Croatian, Montenegrin and Bosnian surname, derived from the title of '' knez''. It may refer to: * House of Knežević, Croatian noble family Knežević is the eighth most frequent surname in C ...

(AstDyS). In the 1995 HCM-analysis by Zappalà, however, ''Annika'' is a member of the

(), a prominent family of stony asteroids and the largest one in the intermediate main belt with more than 5,000 members. It orbits the Sun in the

central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known as ...

main-belt at a distance of 2.1–3.1 AU once every 4 years and 2 months (1,523 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 2.59 AU). Its orbit has an eccentricity of 0.18 and an inclination of 11 ° with respect to the ecliptic. The body's observation arc begins with its official discovery observation at

Heidelberg Observatory Heidelberg (; Palatine German: ') is a city in the German state of Baden-Württemberg, situated on the river Neckar in south-west Germany. As of the 2016 census, its population was 159,914, of which roughly a quarter consisted of students. ...

on 6 February 1916.

Naming

"Annika" is a common German feminine given name. Any reference to a person or occurrence for the naming of this minor planet 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 Na ...

, ''Annika'' is one of 120 asteroids for which no official naming citation has been published. All of these asteroids have low numbers, the first being . The last asteroid with a name of unknown meaning is . They were discovered between 1876 and the 1930s, predominantly by astronomers Auguste Charlois,

Johann Palisa Johann Palisa (6 December 1848 – 2 May 1925) was an Austrian astronomer, born in Troppau, Austrian Silesia, now Czech Republic. He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 Gel ...

and Karl Reinmuth.

Physical characteristics

In the Tholen-like taxonomy of the

Small Solar System Objects Spectroscopic Survey An asteroid spectral type is assigned to asteroids based on their emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiated ...

(S3OS2), ''Annika'' is a common, stony S-type asteroid, while in the SMASS-like taxonomic variant of the S3OS2 survey, it is an Sl-subtype which transitions from the S-type to the uncommon

L-type asteroid L-type asteroids are relatively uncommon asteroids with a strongly reddish spectrum shortwards of 0.75 μm, and a featureless flat spectrum longwards of this. In comparison with the K-type, they exhibit a more reddish spectrum at visible wavele ...

Rotation period

In October 2002, a rotational lightcurve of ''Annika'' was obtained from photometric observations by Colin Bembrick at Mount Tarana Observatory , Australia, in collaboration with Greg Bolt and Tom Richards near Perth and Melbourne, respectively. Lightcurve analysis gave a well-defined

of hours with a brightness variation of magnitude (). This period was confirmed by Gérald Rousseau in March 2012, who determined a very similar period of hours with an amplitude of magnitude ().

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Japanese Akari satellite, ''Annika'' measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The ''Collaborative Asteroid Lightcurve Link'' derives an albedo of 0.2062 and a diameter of 22.20 kilometers based on an absolute magnitude of 10.6. Alternative mean-diameter measurements published by the WISE team include (), (), () and () with corresponding albedos of (), (), () and (). On 26 August 2010, an asteroid occultation of ''Annika'' gave a best-fit ellipse dimension of (). These timed observations are taken when the asteroid passes in front of a distant star. However, these two observations have received a poor quality rating.

References

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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:Annika, 817 000817 Discoveries by Max Wolf Named minor planets 000817 19160206