3309 Brorfelde, provisional designation , is a nearly spheroidal,

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that t ...

Hungaria

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

from the inner regions of the asteroid belt, approximately 4 kilometers in diameter. It was discovered on 28 January 1982, by Danish astronomers Kaare Jensen and

Karl Augustesen Karl A. Augustesen (born 1945) is a Danish astronomer and co-discoverer of minor planets. Working at Brorfelde Observatory, he is credited by the Minor Planet Center with the discovery of 6 numbered asteroid An asteroid is a minor planet of ...

at the

Brorfelde Observatory Brorfelde Observatory ( da, Brorfelde Observatoriet; obs. code: 054) is an astronomical observatory located in Brorfelde near Holbæk, Denmark. It is home to the Brorfelde Schmidt Telescope and was run as a branch of the Copenhagen Uni ...

near Holbæk, Denmark. It was named for the discovering observatory and the village where it is located.

Orbit and classification

''Brorfelde'' is a bright stony asteroid and member of the

Hungaria family The Hungaria asteroids, also known as the Hungaria group, are a dynamical group of asteroids in the asteroid belt which orbit the Sun with a semi-major axis (longest radius of an ellipse) between 1.78 and 2.00 astronomical units (AU). They are t ...

, which form the innermost dense concentration of asteroids in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. It orbits the Sun at a distance of 1.7–1.9 AU once every 2 years and 5 months (895 days). Its orbit has an eccentricity of 0.05 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 Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 21 ° with respect to the ecliptic. 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, as no precoveries were taken, and no prior identifications were made.

Physical characteristics

On the SMASS taxonomic scheme, ''Brorfelde'' is a common stony

S-type asteroid S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the second ...

Photometry

Between 2005 and 2010, astronomers Brian Warner and

Petr Pravec Petr Pravec (born September 17, 1967) is a Czech astronomer and a discoverer of minor planets, born in Třinec, Czech Republic. Pravec is a prolific discoverer of binary asteroids, expert in photometric observations and rotational lightcurves a ...

obtained a large number of rotational lightcurves of ''Brorfelde''. Best rated lightcurve analysis gave 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 ...

between 2.5041 and 2.5046 hours with a brightness amplitude between 0.09 and 0.13 in magnitude, indicating that the body has a nearly spheroidal shape (). These results superseded photometric observations taken by

Wiesław Z. Wiśniewski Wiesław Z. Wiśniewski (May 2, 1931 in Poland – February 28, 1994 in Tucson, Arizona, United States) was a Polish astronomer. Wisniewski was born and educated in Poland. He survived the Nazi occupation and many of his later insights and viewpo ...

in the 1990s (), and by Federico Manzini and René Roy in 2005 and 2009, respectively (), as well as observations taken at the

Palomar Transient Factory The Palomar Transient Factory (PTF, obs. code: I41), was an astronomical survey using a wide-field survey camera designed to search for optical transient and variable sources such as variable stars, supernovae, asteroids and comets. The projec ...

in 2010, which gave an incorrect period solution of more than 9 hours ().

Satellite

During the photometric observation in 2005, it was revealed that ''Brorfelde'' is a binary asteroid. Its

asteroid moon A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. , there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons (and binary objects, in general) are important ...

has an orbital period of hours, and measures approximately 1 kilometer in diameter, based on a mean-diameter ratio of for the system's secondary and primary body. In January 2014, repeated observations by Brian Warner confirmed a period of 2.503 and 18.51 hours for the primary and secondary, respectively (), with several online-published lightcurve plots.

Diameter and albedo

According to the survey carried out by 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 2011, ...

with its subsequent NEOWISE mission, ''Brorfelde'' measures 3.78 kilometers in diameter, and its surface has an

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, 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 ...

of 0.46 (most recent result only). The ''Collaborative Asteroid Lightcurve Link'' derives an albedo of 0.2747 and a diameter of 3.91 kilometers with an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of 14.062.

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 on the occasion of the Brorfelde Observatory's 40th anniversary. ''Brorfelde'' was the observatory's first minor planet discovery. The approved naming citation was published by the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function ...

on 7 September 1987 ().

Orbit and classification

Physical characteristics

Photometry

Satellite

Diameter and albedo

Naming

Notes

References

External links