1192 Prisma, provisional designation , is an elongated Phocaea asteroid 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 ...

, approximately 7 kilometers in diameter. It was discovered by German astronomer Friedrich Schwassmann at the Bergedorf Observatory in Hamburg on 17 March 1931. The asteroid was named after the ''Bergedorf Spectral Catalogue'', an

astronomical catalog An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, Galaxy morphological classification, morphology, origin, means of detection, or method of discovery. The olde ...

Classification and orbit

''Prisma'' is a member of the Phocaea family (), a prominent family of

S-type asteroid S-type (stony-type or silicaceous-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 ...

s with their largest members being 25 Phocaea and 587 Hypsipyle. There are many Mars-crossers among this family of relatively eccentric inner main-belt asteroids . The asteroid orbits the Sun at a distance of 1.8–3.0 AU once every 3 years and 8 months (1,329 days). 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 0.26 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 24 ° 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 at Bergedorf, one week after its official discovery observation.

Physical characteristics

Rotation, shape and pole

Photometric observations of ''Prisma'' gave a well defined 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 ...

with a period between 6.546 and 6.558 hours and a high brightness variation of 0.85–1.16

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 ...

, which strongly indicates that the body has an elongated, non-spheroidal shape (). A modeled lightcurve based on optical data from a large collaboration network also found a spin axis of (133.0°, −78.0°) in

ecliptic coordinates In astronomy, the ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small So ...

(λ, β) ().

Diameter and albedo

According to the surveys carried out by the Japanese

Akari AKARI (ASTRO-F) was an infrared astronomy satellite developed by Japan Aerospace Exploration Agency, in cooperation with institutes of Europe and Korea. It was launched on 21 February 2006, at 21:28 UTC (06:28, 22 February JST) by M-V rocket ...

satellite, and 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 ...

with its subsequent

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, ''Prisma'' measures between 7.38 and 9.27 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 ...

between 0.144 and 0.220. The ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo of 0.23 and calculates a diameter of 7.22 kilometers based on an absolute magnitude of 12.92.

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 "Prisma" (

prism PRISM is a code name for a program under which the United States National Security Agency (NSA) collects internet communications from various U.S. internet companies. The program is also known by the SIGAD . PRISM collects stored internet ...

) in honour of the ''Bergedorf Spectral Catalogue'' (), as prisms are one method of obtaining spectra. The official naming citation was also published in Paul Herget's '' The Names of the Minor Planets'' in 1955 ().

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Observatoire de Genève, Raoul Behrend

– Minor Planet Center * * {{DEFAULTSORT:Prisma 001192 Discoveries by Friedrich Karl Arnold Schwassmann Named minor planets 19310317