211 Isolda

211 Isolda is a very large, dark main-belt asteroid. It is classified as a C-type asteroid and is probably composed of primitive carbonaceous material. The spectra of the asteroid displays evidence of aqueous alteration.^[6]

211 Isolda

Orbital diagram
Discovery
Discovered by	Johann Palisa
Discovery date	10 December 1879
Designations
MPC designation	(211) Isolda
Pronunciation	/ɪˈzoʊldə/[1]
Named after	Iseult
Alternative designations	A879 XA, 1912 AB 1912 BA, 1950 FM
Minor planet category	Main belt
Adjectives	Isoldian /ɪˈzoʊldiən/[2]
Orbital characteristics[3]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc	136.19 yr (49742 d)
Aphelion	3.53270 AU (528.484 Gm)
Perihelion	2.5514 AU (381.68 Gm)
Semi-major axis	3.04205 AU (455.084 Gm)
Eccentricity	0.16129
Orbital period (sidereal)	5.31 yr (1938.0 d)
Average orbital speed	17.08 km/s
Mean anomaly	260.142°
Mean motion	0° 11m 8.74s / day
Inclination	3.8856°
Longitude of ascending node	263.644°
Argument of perihelion	173.522°
Physical characteristics
Dimensions	143.19±5.1 km[3] 149.81 ± 6.10 km[4]
Mass	(4.49 ± 2.43) × 1018 kg[4]
Mean density	2.54 ± 1.41 g/cm3[4]
Synodic rotation period	18.365 h (0.7652 d)
Geometric albedo	0.0602±0.004[3] 0.0598 ± 0.0218[5]
Spectral type	C[5] (Tholen)
Absolute magnitude (H)	7.89,[3] 7.90[5]

It was discovered by Austrian astronomer Johann Palisa on 10 December 1879, in Pola, and is possibly named after Isolde, heroine of the legend of Tristan and Iseult.^[7]

In 2001, the asteroid was detected by radar from the Arecibo Observatory at a distance of 1.78 AU. The resulting data yielded an effective diameter of 143 ± 16 km.^[8]

Between 2009 and 2022, 211 Isolda has been observed to occult seven stars.^{[citation needed]}