783 Nora ( ''prov. designation'': ''or'' ) is a dark

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 inner 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 ...

. It was discovered by Austrian astronomer

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 G ...

at the

Vienna Observatory The Vienna Observatory () is an astronomical observatory in Vienna, Austria. It is part of the University of Vienna. The first observatory was built in 1753–1754 on the roof of one of the university buildings. A new observatory was built betwe ...

on 18 March 1914. 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 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 55.5 hours and measures approximately in diameter. It was likely named after

Nora Helmer Nora Helmer is a fictional character of Henrik Ibsen's 1879 play ''A Doll's House''. She is introduced as a seemingly devoted wife and mother, living in a comfortable middle-class home with her husband Torvald, a recently promoted bank manager, ...

, principal character in the play ''

A Doll's House ''A Doll's House'' (Danish language, Danish and ; also translated as ''A Doll House'') is a three-act Play (theatre), play written by Norwegian playwright Henrik Ibsen. It premiered at the Royal Danish Theatre in Copenhagen, Denmark, on 21 De ...

'' by Norwegian poet

Henrik Ibsen Henrik Johan Ibsen (; ; 20 March 1828 – 23 May 1906) was a Norwegian playwright, poet and actor. Ibsen is considered the world's pre-eminent dramatist of the 19th century and is often referred to as "the father of modern drama." He pioneered ...

Orbit and classification

''Nora'' 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 __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 quantities ...

. It orbits the Sun in the inner asteroid belt at a distance of 1.8–2.9 AU once every 3 years and 7 months (1,310 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 2.34 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 0.23 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 9 ° 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 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 first observation as at

Heidelberg Observatory Heidelberg (; ; ) is the List of cities in Baden-Württemberg by population, fifth-largest city in the States of Germany, German state of Baden-Württemberg, and with a population of about 163,000, of which roughly a quarter consists of studen ...

on 28 August 1911, more than two years prior to its official discovery observation at

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 likely named after

, the heroine in the play ''

'' (1879) by Norwegian poet

(1828–1906). The name was given by the discoverer's friends. The was also mentioned in ''

The Names of the Minor Planets Paul Herget (January 30, 1908 – August 27, 1981) was an American astronomer and director of the Cincinnati Observatory, who established the Minor Planet Center after World War II. Career Herget taught astronomy at the University of Cincinna ...

'' by

Paul Herget Paul Herget (January 30, 1908 – August 27, 1981) was an American astronomer and director of the Cincinnati Observatory, who established the Minor Planet Center after World War II. Career Herget taught astronomy at the University of Cincinna ...

in 1955 ().

Physical characteristics

In the Bus–Binzel

SMASS classification An asteroid spectral type is assigned to asteroids based on their reflectance spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally different ...

, ''Nora'' is a common, carbonaceous

. In the

Tholen classification An asteroid spectral type is assigned to asteroids based on their reflectance spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally different ...

it is one of few asteroids considered unclassifiable.

Rotation period

In March 2018, 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 ''Nora'' was obtained from photometric observations by

Tom Polakis Tom or TOM may refer to: * Tom (given name), including a list of people and fictional characters with the name. Arts and entertainment Film and television * ''Tom'' (1973 film), or ''The Bad Bunch'', a blaxploitation film * ''Tom'' (2002 film) ...

at the Command Module Observatory in Arizona. Lightcurve analysis gave a

of hours with a low 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 ...

(). The result supersedes previous observations by European astronomers at the La Silla, Haute Provence and

Hoher List The Hoher List is a stratovolcano, , near the town of Daun in the Eifel region. The hill is in the county of Vulkaneifel in the German state of Rhineland-Palatinate. Location The Hoher List lies in the Volcanic Eifel, part of the Eifel Mountain ...

observatories during the 1990s which gave two periods of and with an amplitude of and magnitude, respectively (). In April 2007, French astronomer Arnaud Leroy determined a period of and a brightness variation of 0.01 magnitude ().

Diameter and albedo

According to the surveys carried out by 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), the Japanese Akari satellite, and 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 ...

, ''Nora'' 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 0.0404 and a diameter of 39.84 kilometers based on an absolute magnitude of 11.1. Alternative mean-diameter measurements published by the WISE team include (), (), (), () and () with corresponding albedos of (), (), (), () and (). On 4 May 2004, 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 f ...

of ''Nora'' gave a best-fit ellipse dimension of (), with a poor quality rating of 1. 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 This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 nu ...

Discovery Circumstances: Numbered Minor Planets (1)-(5000)
– Minor Planet Center * * {{DEFAULTSORT:Nora 000783 Discoveries by Johann Palisa Named minor planets 000783 000783 19140318