88 Thisbe

88 Thisbe is the 13th largest main-belt asteroid. It was discovered by C. H. F. Peters on 15 June 1866, and named after Thisbe, heroine of a Roman fable. This asteroid is orbiting the Sun at a distance of 2.768 AU with a period of 4.60 years and an orbital eccentricity (ovalness) of 0.165. The orbital plane is inclined at an angle of 5.219° to the ecliptic.

88 Thisbe

Discovery
Discovered by	Christian Heinrich Friedrich Peters
Discovery date	15 June 1866
Designations
MPC designation	(88) Thisbe
Pronunciation	/ˈθɪzbiː/[1]
Named after	Thisbē
Minor planet category	Main belt
Adjectives	Thisbean /θɪzˈbiːən/, /ˈθɪzbiən/
Orbital characteristics[2]
Epoch 31 December 2006 (JD 2454100.5)
Aphelion	482.242 Gm (3.224 AU)
Perihelion	345.809 Gm (2.312 AU)
Semi-major axis	414.025 Gm (2.768 AU)
Eccentricity	0.165
Orbital period (sidereal)	1,681.709 d (4.60 yr)
Mean anomaly	165.454°
Inclination	5.219°
Longitude of ascending node	276.765°
Argument of perihelion	36.591°
Physical characteristics
Dimensions	(255×232×193)±12 km[3]
Mean diameter	218±3 km[4] 225 km[3] 232 km (Dunham)[2]
Flattening	0.19[a]
Mass	(11.6±2.2)×1018 kg[4] 18.3×1018 kg[3] 1.5×1019 kg[5][b]
Mean density	2.14±0.42 g/cm3[4] 3.06±0.52 g/cm3[3]
Synodic rotation period	6.04[6] h
Geometric albedo	0.057[4] 0.067[7]
Spectral type	B[2]
Absolute magnitude (H)	7.04[2]

On 7 October 1981, asteroid 88 Thisbe was observed to occult the 9th-magnitude star SAO 187124 from 12 sites. The timing of the different chords across the asteroid provided a diameter estimate of 232±12 km. This is 10% larger than the diameter estimate based on radiometric techniques.^[8][9][10] During 2000, 88 Thisbe was observed by radar from the Arecibo Observatory. The return signal matched an effective diameter of 207 ± 22 km. This is consistent with the asteroid dimensions computed through other means.^[11]

Photometric observations of this asteroid during 1977 gave a light curve with a period of 6.0422 ± 0.006 hours and a brightness variation of 0.19 in magnitude.^[6]

Perturbation

Thisbe has been perturbed by asteroid 7 Iris and in 2001 Michalak estimated it to have a mass of 15×10¹⁸ kg.^[5][b] But Iris is strongly perturbed by many minor planets such as 10 Hygiea and 15 Eunomia.^[5]

In 2008, Baer estimated Thisbe to have a mass of 10.5×10¹⁸ kg.^[3] In 2011 Baer revised this to 18.3×10¹⁸ kg with an uncertainty of 1.1×10¹⁸ kg.^[3]

Notes

1. Flattening derived from the maximum aspect ratio (c/a): ${\displaystyle f=1-{\frac {c}{a}}}$, where (c/a) = 0.81±0.07.^[4]
2. (7.4 ± 1.3)×10⁻¹² M_☉ = 1.47×10¹⁹ kg