107 Camilla

107 Camilla is one of the largest asteroids from the outermost edge of the asteroid belt, approximately 250 kilometers (160 miles) in diameter. It is a member of the Sylvia family and located within the Cybele group. It was discovered on 17 November 1868, by English astronomer Norman Pogson at Madras Observatory, India, and named after Camilla, Queen of the Volsci in Roman mythology.^[4][2] The X-type asteroid is a rare triple asteroid with two minor-planet moons discovered in 2001 and 2016, respectively. It is elongated in shape and has a short rotation period of 4.8 hours.^[18]

107 Camilla

Lightcurve-based 3-D model of Camilla
Discovery[1][2]
Discovered by	N. R. Pogson
Discovery site	Madras Obs.
Discovery date	17 November 1868
Designations
MPC designation	(107) Camilla
Pronunciation	/kəˈmɪlə/[3]
Named after	Camilla (Roman mythology)[4]
Alternative designations	A868 WA, 1893 QA 1938 OG, 1949 HD1
Minor planet category	main-belt · (outer)[1] Sylvia · Cybele
Adjectives	Camillian or Camillean, /kəˈmɪliən/
Orbital characteristics[1]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	149.17 yr (54,485 d)
Aphelion	3.7202 AU
Perihelion	3.2622 AU
Semi-major axis	3.4912 AU
Eccentricity	0.0656
Orbital period (sidereal)	6.52 yr (2,383 d)
Mean anomaly	265.91°
Mean motion	0° 9m 3.96s / day
Inclination	10.001°
Longitude of ascending node	172.61°
Argument of perihelion	306.77°
Known satellites	2[5][6][7]
Physical characteristics
Dimensions	285 km × 205 km × 170 km[8] 344 km × 246 km × 205 km[9]
Mean diameter	254±12 km[10] 200.37±3.51 km[11] 210.370±8.326 km[12] 222.62±17.1 km[13] 241.6±35.0 km[14] 243.3±12.4 km[15]
Mass	(11.2±0.1)×1018 kg[10][9]
Mean density	1.28±0.04 g/cm3[10] 1.40±0.30 g/cm3[9]
Synodic rotation period	4.844 h[16][17][a]
Geometric albedo	0.043±0.012[15] 0.045±0.019[14] 0.0525±0.009[13] 0.059±0.012[12] 0.065±0.003[11]
Spectral type	X (SMASS)[1][18] C (Tholen) P (WISE)[19] B–V = 0.705[1] U–B = 0.298[1]
Apparent magnitude	11.53[20]
Absolute magnitude (H)	7.08[1][11][13][14][15][19] 7.1±0.02[18][21][16]

Physical characteristics

Camilla has a very dark surface and primitive carbonaceous composition.

A large number of rotational lightcurves of have been obtained from photometric observations since the 1980s.^[22] Best rated results gave a short rotation period of 4.844 hours with a brightness amplitude between 0.32 and 0.53 magnitude.^[16][17][a]

Lightcurve analysis indicates that Camilla's pole most likely points towards ecliptic coordinates (β, λ) = (+51°, 72°) with a 10° uncertainty,^[8] which gives it an axial tilt of 29°. Follow-up modeling of photometric data gave similar results.^[23][24][25]

Diameter and albedo

10μ radiometric data collected from Kitt Peak in 1975 gave a first diameter estimate of 209 km.^[26] According to the space-based surveys carried out by the Japanese Akari satellite, the Infrared Astronomical Satellite IRAS and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer,^{[11][12][13][19][21]} as well as observations by the Keck Observatory and photometric modeling,^{[14][15][27][23][24][28][29]} Camilla measures between 185 and 247 kilometers in diameter and its surface has an albedo between 0.160 and 0.294.^[18]

Satellites

Camilla is the 6th triple asteroid that has been discovered in the asteroid belt, after 87 Sylvia, 45 Eugenia, 216 Kleopatra, 93 Minerva and 130 Elektra (a quaternary).

Outer satellite

S/2001 (107) 1

Discovery[6]
Discovered by	A. Storrs, F. Vilas, R. Landis, E. Wells, C. Woods, B. Zellner, and M. Gaffey
Discovery date	1 March 2001
Orbital characteristics[10]
Observation arc	5642 days
Semi-major axis	1247.8±1.3 km
Eccentricity	0.000±0.004
Orbital period (sidereal)	3.71234±0.00001 d
Inclination	16.0°±0.8°
Physical characteristics
Mean diameter	12.7±3.5 km, assuming equal albedos and DCamilla = 254 km[10] 16±6 km[9] ~ 11 ± 2 km[27]
Mass	~1.5×1015 kg[30]
Absolute magnitude (H)	13.18[27]

On 1 March 2001, a minor-planet moon of Camilla was found by A. Storrs, F. Vilas, R. Landis, E. Wells, C. Woods, B. Zellner, and M. Gaffey using the Hubble Space Telescope.^[6] It has the provisional designation S/2001 (107) 1 but has not yet received an official name.

Later observations in September 2005 with the Very Large Telescope (VLT) allowed the determination of an orbit. In addition to the data in the infobox at right, the inclination was found to be 3 ± 1° with respect to an axis pointing towards (β, λ) = (+55°, 75°). Given the ~10° uncertainty in the actual rotational axis of Camilla, one can say that the orbit's inclination is less than 10°.

The satellite is estimated to measure about 11 km in diameter.^[27] Assuming a similar density to the primary, this would give it an approximate mass of ~1.5×10¹⁵ kg. It has a similar colour to the primary.^[6]

Inner satellite

S/2016 (107) 1

Discovery[7]
Discovered by	M. Marsset, B. Carry, B. Yang, F. Marchis, P. Vernazza, C. Dumas, J. Berthier, F. Vachier
Discovery date	29 May 2015
Orbital characteristics[10]
Observation arc	428 days
Semi-major axis	643.8±1.3 km
Eccentricity	0.18+0.08 −0.06
Orbital period (sidereal)	1.376±0.005 d
Inclination	27.7°±7.3°
Satellite of	107 Camilla
Physical characteristics
Mean diameter	4.0±1.2 km, assuming equal albedos and DCamilla = 254 km[10]

In 2016, the discovery of a second satellite of Camilla was reported by astronomers at Cerro Paranal's Very Large Telescope in Chile. It has the provisional designation S/2016 (107) 1.^[7]

Observations were taken between 29 May 2015 and 30 July 2016, using the VLT-SPHERE, the principal instrument attached to the 8-meter "Melipal" (UT3) unit of the VLT. On 3 out of 5 observation sessions, the new satellite could be detected.^[7] The body's orbit has a semi-major axis of 340 kilometers.^[5]

Notes

1. Pietschnig (2011) web: Photometric observations from 28 March 2007. Rotation period 4.844±0.003 hours with a brightness amplitude of 0.47 magnitude. Quality code of 3. Summary figures at Collaborative Asteroid Lightcurve Link (CALL)