1192 Prisma

1192 Prisma, provisional designation 1931 FE, is an elongated Phocaea asteroid from the inner regions of the asteroid belt, approximately 7 kilometers in diameter. It was discovered by German astronomer Friedrich Schwassmann at the Bergedorf Observatory in Hamburg on 17 March 1931.^[12] The asteroid was named after the Bergedorf Spectral Catalogue, an astronomical catalog.^[2]

1192 Prisma

Modelled shape of Prisma from its lightcurve
Discovery[1]
Discovered by	A. Schwassmann
Discovery site	Bergedorf Obs.
Discovery date	17 March 1931
Designations
MPC designation	(1192) Prisma
Named after	Bergedorf Spectral Catalogue (astronomical catalog)[2]
Alternative designations	1931 FE
Minor planet category	main-belt · (inner) Phocaea[3][4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	85.77 yr (31,328 days)
Aphelion	2.9762 AU
Perihelion	1.7561 AU
Semi-major axis	2.3661 AU
Eccentricity	0.2578
Orbital period (sidereal)	3.64 yr (1,329 days)
Mean anomaly	297.62°
Mean motion	0° 16m 14.88s / day
Inclination	23.902°
Longitude of ascending node	1.3517°
Argument of perihelion	131.44°
Physical characteristics
Dimensions	7.22 km (calculated)[3] 7.377±0.193 km[5] 9.27±0.25 km[6]
Synodic rotation period	6.546±0.0170 h[7] 6.558 h[8] 6.55836±0.00005 h[9][10]
Geometric albedo	0.144±0.009[6] 0.220±0.022[5] 0.23 (assumed)[3]
Spectral type	S[3]
Absolute magnitude (H)	12.497±0.008 (R)[7] · 12.87±0.47[11] · 12.92[1][3][5][6]

Classification and orbit

Prisma is a member of the Phocaea family (701), a prominent family of S-type asteroids 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 .^[13]

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 of 0.26 and an inclination of 24° with respect to the ecliptic.^[1] The body's observation arc begins at Bergedorf, one week after its official discovery observation.^[12]

Physical characteristics

Rotation, shape and pole

Photometric observations of Prisma gave a well defined rotational lightcurve with a period between 6.546 and 6.558 hours and a high brightness variation of 0.85–1.16 magnitude, which strongly indicates that the body has an elongated, non-spheroidal shape (U=3/3).^[7][8]

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 (λ, β) (Q=n.a.).^[9][10]

Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Prisma measures between 7.38 and 9.27 kilometers in diameter and its surface has an albedo between 0.144 and 0.220.^[5][6] 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.^[3]

Naming

This minor planet was named "Prisma" (prism) in honour of the Bergedorf Spectral Catalogue (German: Bergedorfer Spektralkatalog), as prisms are one method of obtaining spectra.^[2] The official naming citation was also published in Paul Herget's The Names of the Minor Planets in 1955 (H 111).^[2]