5535 Annefrank

5535 Annefrank (/ˌænˈfræŋk/ ^ⓘ an-FRANK), provisional designation 1942 EM, is a stony Florian asteroid and suspected contact binary from the inner asteroid belt, approximately 4.5 kilometers in diameter. It was used as a target to practice the flyby technique that the Stardust space probe would later use on the comet Wild 2.^[8]

5535 Annefrank

Annefrank viewed by Stardust in 2002
Discovery[1]
Discovered by	Karl Wilhelm Reinmuth
Discovery site	Heidelberg Obs.
Discovery date	23 March 1942
Designations
MPC designation	(5535) Annefrank
Named after	Anne Frank (Holocaust victim)[2]
Alternative designations	1942 EM · 1978 EK6 1986 TV14 · 1991 BO2
Minor planet category	main-belt · Flora[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	75.02 yr (27,400 days)
Aphelion	2.3527 AU
Perihelion	2.0721 AU
Semi-major axis	2.2124 AU
Eccentricity	0.0634
Orbital period (sidereal)	3.29 yr (1,202 days)
Mean anomaly	23.021°
Mean motion	0° 17m 58.2s / day
Inclination	4.2473°
Longitude of ascending node	120.64°
Argument of perihelion	9.1351°
Physical characteristics
Dimensions	(6.6 x 5.0 x 3.4 km)[1] 4.34±0.23 km[4] 4.8 km[1] 4.94 km (calculated)[3]
Synodic rotation period	15.12 h[5] 15.156±0.0474 h[6] 21.33±0.990 h[7]
Geometric albedo	0.21±0.03[8] 0.24 (assumed)[3] 0.279±0.092[9] 0.311±0.056[4]
Spectral type	S[3][8]
Absolute magnitude (H)	13.650±0.120 (R)[7] · 13.679±0.001 (R)[6] · 13.7[1][3][4] · 13.88±0.32[10]

Animation of Stardust 's trajectory from 7 February 1999 to 7 April 2011
   Stardust  ·   81P/Wild ·   Earth ·   5535 Annefrank  ·   Tempel 1

The asteroid was discovered 23 March 1942, by German astronomer Karl Reinmuth at Heidelberg Observatory in southwest Germany.^[11] It was named after Anne Frank, a victim of the Holocaust.^[2]

Orbit and classification

Annefrank is a member of the Flora family, one of the largest collisional populations of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 2.1–2.4 AU once every 3 years and 3 months (1,202 days). Its orbit has an eccentricity of 0.06 and an inclination of 4° with respect to the ecliptic.^[1]

The body's observation arc begins at Crimea–Nauchnij in 1978, with its identification as 1978 EK6, 36 years after its official discovery observation at Heidelberg.^[11]

Physical characteristics

Annefrank has been characterized as a common S-type asteroid.^[3][8]

Diameter, albedo and shape

On 2 November 2002, the Stardust space probe flew past Annefrank at a distance of 3079 km. Its images show the asteroid to be 6.6 × 5.0 × 3.4 km, twice as big as previously thought, and its main body shaped like a triangular prism with several visible impact craters.^[8] From the photographs, the albedo of Annefrank was computed to be between 0.18 and 0.24.^[8] Preliminary analysis of the Stardust imagery suggests that Annefrank may be a contact binary, although other possible explanations exist for its observed shape.^[8]

Rotation and poles

In October 2006, ground-based photometric observations were used in an attempt to measure Annefrank's rotational period. Analysis of the ambiguous lightcurve gave a period of 15.12 hours and a brightness variation of 0.25 magnitude with two alternative period solutions of 12 and 22.8 hours, respectively (U=2).^[3][5]

In January 2014, photometric observations at the Palomar Transient Factory gave a rotation period of 15.156 and 21.33 hours with an amplitude of 0.17 and 0.20 magnitude, respectively (U=2/2).^[6][7]

The lightcurve data suggests that Annefrank is not Lambertian, meaning that surface features, such as shadows from boulders and craters, play a role in the object's perceived brightness and not just the asteroid's relative size when seen from that orientation.^[5]

The body's shortest axis is approximately aligned perpendicular to its orbital plane.^[8]

Naming

This minor planet was named after Anne Frank, the German-Dutch-Jewish diarist who died in a Nazi concentration camp during the Second World War.^[2] The official naming citation was published by the Minor Planet Center on 14 May 1995 (M.P.C. 25230).^[12]