826 Henrika ( ''prov. designation'': ''or'' ) is a

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 central 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 ...

. It was discovered by German astronomer Max Wolf 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 ...

on 28 April 1916. The carbonaceous

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 ...

has a rotation period of 5.98 hours and measures approximately in diameter. Any reference to the origin of the asteroid's name is unknown.

Orbit and classification

''Henrika'' is a non-

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 ...

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 __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 ...

. It orbits the Sun in the central asteroid belt at a distance of 2.2–3.3 AU once every 4 years and 6 months (1,631 days; semi-major axis of 2.71 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 0.21 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 7 ° 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 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 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 student ...

on 2 July 1921, more than five years after its official discovery observation.

Naming

Any reference of 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 ...

name to a person or occurrence is unknown.

Unknown meaning

Among the many thousands of named minor planets, ''Henrika'' is one of 120 asteroids for which has been published. All of these asteroids have low numbers, the first one being . The last asteroid with a name of unknown meaning is . They 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 Tir ...

, Johann Palisa, Max Wolf 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 Heid ...

Physical characteristics

In the Bus–Binzel

SMASS classification 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 differentiat ...

, ''Henrika'' is a common, carbonaceous

, with an untypically 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 ...

''(see below)'' for such

spectral class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

. In a taxonomic classification based on MOVIS near-infrared colors, ''Henrika'' could not be assigned a final class and was labelled as undefined (U).

Rotation period

In April 210, a 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 ''Henrika'' was obtained from six nights of photometric observations by

Frederick Pilcher Frederick Pilcher (born 1939) is a retired physics professor and a prolific photometrist of minor planets at his private Organ Mesa Observatory in New Mexico, United States. Biography A graduate of University of Kansas, Frederick Pilcher has ...

at the Organ Mesa Observatory in New Mexico. Analysis of the classically shaped bimodal lightcurve gave a well-defined rotation period of hours with a brightness variation 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 ...

(). During the same apparition, a virtually identical period of hours with an amplitude of magnitude () was determined by Kenda Albers and colleges of the Rose-Hulman Institute of Technology at the Oakley Southern Sky Observatory in Australia.

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite

IRAS The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...

, and the Japanese Akari satellite, and 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 201 ...

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 201 ...

(WISE), ''Henrika'' measures (), () and () kilometers in diameter and its surface has an

of (), () and (), respectively. Alternative mean-diameters published by the WISE team include (), () and () with corresponding albedos of (), () and (). The ''Collaborative Asteroid Lightcurve Link'' derives an albedo of 0.1103 and a diameter of 19.15 kilometers based 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 11.6. An

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 ...

s of ''Henrika'' from 19 January 2010, gave a best-fit ellipse dimension of (). These timed observations are taken when the asteroid passes in front of a distant star.

Notes

References

External links

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

– Minor Planet Center * * {{DEFAULTSORT:Henrika 000826 Discoveries by Max Wolf Named minor planets 000826 19160428