(216) Kleopatra

216 Kleopatra
216 Kleopatra VLT (2021), deconvolved.pdf
Discovery [1]
Discovered byJ. Palisa
Discovery sitePola Obs.
Discovery date10 April 1880
(216) Kleopatra
Named after
Cleopatra (Egyptian queen)[2]
A880 GB · 1905 OA
1910 RA
main-belt[1][3] · (central)[4]
AdjectivesKleopatrian, Kleopatrean
Orbital characteristics[3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc137.60 yr (50,259 d)
Aphelion3.4951 AU
Perihelion2.0931 AU
2.7941 AU
4.67 yr (1,706 d)
0° 12m 39.6s / day
Known satellites2 (Alexhelios · Cleoselene)
Physical characteristics
Dimensionsc/a = 0.18±0.02[7]
(276 × 94 × 78) ± 15% km[8]
Mean diameter
118±2 km[7]
122±30 km[8]
103±4 km[9]
121.6±1.6 km[10]
135±2 km[11]
Mass(3.0±0.3)×1018 kg[7]
(2.97±0.02)×1018 kg[12][8]
Mean density
3.45±0.41 g/cm3[7]
ca. 4.5 g/cm3 (most likely between 3.6±0.4 g/cm3 for D = 135 km and 5.4±0.4 g/cm3 for D = 109 km)[8]
5.385280±0.000001 h[8]
0.152 (calculated)[7]
M (Tholen)[3] · Xe (SMASS)[3]
B–V = 0.713[3]
U–B = 0.238[3]
7.35±0.02[4][15][17] · 7.45[13]

216 Kleopatra is a large M-type asteroid with a mean diameter of 120 kilometers (75 miles) and is noted for its elongate bone or dumbbell shape.[18][19][8][20] It was discovered on 10 April 1880 by Austrian astronomer Johann Palisa at the Austrian Naval Pola Observatory, in what is now Pula, Croatia, and was named after Cleopatra, the famous Egyptian queen.[1] It has two small minor-planet moons which were discovered in 2008 and later named Alexhelios and Cleoselene.

Orbit and classification[]

Kleopatra is a non-family asteroid from the main belt's background population.[5] It orbits the Sun in the central asteroid belt at a distance of 2.1–3.5 AU once every 4 years and 8 months (1,706 days; semi-major axis of 2.79 AU). Its orbit has an eccentricity of 0.25 and an inclination of 13° with respect to the ecliptic.[3] The body's observation arc begins at Leipzig Observatory (534) on 20 April 1880, ten days after to its official discovery observation at Pola Observatory.[1]

216 Kleopatra-orbit.png

Physical characteristics[]

Size and Shape[]

Kleopatra is a relatively large asteroid, with a mean (volume-equivalent) diameter of 120±2 km[8][20] and an unusually elongate shape.

Animated view of Kleopatra as viewed from 20° N latitude.
Animated view of Kleopatra as viewed from 20° S latitude.

The initial mapping of its elongated shape was indicated by stellar occultation observations from eight distinct locations on 19 January 1991.[21] Subsequent observations with the ESO 3.6 m Telescope at La Silla, run by the European Southern Observatory, were interpreted to show a double source with two distinct lobes of similar size.[22] These results were disputed when radar observations at the Arecibo Observatory showed that the two lobes of the asteroid are connected, resembling the shape of a ham-bone. The radar observations provided a detailed shape model that appeared on the cover of Science Magazine.[18] Later models suggested that Kleopatra was more elongate and the most recent models using radar delay-Doppler imaging, adaptive optics, and stellar occultations provide dimensions of 267 × 61 × 48 km.[23][8][20]


In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty.[24] In September 2008, Franck Marchis and his collaborators announced that by using the Keck Observatory's adaptive optics system, they had discovered two moons orbiting Kleopatra.[25] In February 2011, the minor-planet moons were named Alexhelios /ˌælɪksˈhliɒs/ (outer) and Cleoselene /ˌklsɪˈln/ (inner), after Cleopatra's children Alexander Helios and Cleopatra Selene II.[1] The outer and inner satellites are about 8.9 ± 1.6 and 6.9 ± 1.6 km in diameter, with periods of 2.7 and 1.8 days, respectively.[26]

Kleopatra and its two moons imaged by VLT-SPHERE in 2017

Mass, Bulk Density, and Composition[]

The presence of two moons provides a way to estimate Kleopatra's mass, although its irregular shape makes the orbital modeling a challenge.[26] The most recent adaptive-optics observations and modeling provides a mass of Kleopatra of (1.49±0.16)×10−12 M, or (2.97±0.32)×1018 kg, which is significantly lower than previously thought.[12] When combined with the best volume estimate for Kleopatra, this indicates a bulk density of 3.38±0.50 g/cm3.[20]

These recent bulk density results call into question the canonical view of Kleopatra as a pure metallic object.[18] Kleopatra's radar albedo suggests a high metal content in the southern hemisphere, but is similar to the more common S- an C-class asteroids along the equator.[8] One way to reconcile these observations is to hypothesize that Kleopatra is a rubble-pile asteroid with significant porosity in dynamic equilibrium.[20]


Size comparison of asteroid Kleopatra with northern Italy

One possible origin that explains Kleopatra's shape, rotation, and moons is that it was created by an oblique impact perhaps 100 million years ago. The increased rotation would have elongated the asteroid and caused Alexhelios to split off. Cleoselene may have split off later, around 10 million years ago. Kleopatra is a contact binary – if it were spinning much faster, the two lobes would separate from each other, making a true binary system.[12][20]

See also[]


  1. ^ a b c d e "216 Kleopatra". Minor Planet Center. Retrieved 22 April 2017.
  2. ^ Schmadel, Lutz D. (2007). "(216) Kleopatra". Dictionary of Minor Planet Names – (216) Kleopatra. Springer Berlin Heidelberg. p. 34. doi:10.1007/978-3-540-29925-7_217. ISBN 978-3-540-00238-3.
  3. ^ a b c d e f g h "JPL Small-Body Database Browser: 216 Kleopatra" (2016-09-20 last obs.). Jet Propulsion Laboratory. Archived from the original on 23 April 2017. Retrieved 22 April 2017.
  4. ^ a b "LCDB Data for (216) Kleopatra". Asteroid Lightcurve Database (LCDB). Retrieved 22 April 2017.
  5. ^ a b "Asteroid 216 Kleopatra". Small Bodies Data Ferret. Retrieved 24 October 2019.
  6. ^ "Cleopatra". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 26 January 2020.
  7. ^ a b c d e P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
  8. ^ a b c d e f g h i Shepard et al (2018) A revised shape model of asteroid (216) Kleopatra, Icarus 311, 197-209
  9. ^ a b c Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. S2CID 46350317. Retrieved 22 April 2017.
  10. ^ a b c Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117.
  11. ^ a b c Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 22 October 2019.
  12. ^ a b c Descamps, P.; Marchis, F.; Berthier, J.; Emery, J. P.; Duchê; ne, G.; et al. (February 2011). "Triplicity and physical characteristics of Asteroid (216) Kleopatra". Icarus. 211 (2): 1022–1033. arXiv:1011.5263. Bibcode:2011Icar..211.1022D. doi:10.1016/j.icarus.2010.11.016. S2CID 119286272.
  13. ^ a b Shevchenko, Vasilij G.; Tedesco, Edward F. (September 2006). "Asteroid albedos deduced from stellar occultations". Icarus. 184 (1): 211–220. Bibcode:2006Icar..184..211S. doi:10.1016/j.icarus.2006.04.006. Retrieved 22 April 2017.
  14. ^ a b c Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. S2CID 35447010.
  15. ^ a b Pravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations". Icarus. 221 (1): 365–387. Bibcode:2012Icar..221..365P. doi:10.1016/j.icarus.2012.07.026. Retrieved 22 April 2017.
  16. ^ Belskaya, I. N.; Fornasier, S.; Tozzi, G. P.; Gil-Hutton, R.; Cellino, A.; Antonyuk, K.; et al. (March 2017). "Refining the asteroid taxonomy by polarimetric observations". Icarus. 284: 30–42. Bibcode:2017Icar..284...30B. doi:10.1016/j.icarus.2016.11.003. Retrieved 22 April 2017.
  17. ^ Harris, A. W.; Young, J. W. (October 1989). "Asteroid lightcurve observations from 1979-1981". Icarus. 81 (2): 314–364. Bibcode:1989Icar...81..314H. doi:10.1016/0019-1035(89)90056-0. ISSN 0019-1035. Retrieved 22 April 2017.
  18. ^ a b c Ostro, Steven J.; Hudson, R. Scott; Nolan, Michael C.; Margot, Jean-Luc; Scheeres, Daniel J.; Campbell, Donald B.; et al. (May 2000). "Radar Observations of Asteroid 216 Kleopatra". Science. 288 (5467): 836–839. Bibcode:2000Sci...288..836O. doi:10.1126/science.288.5467.836. PMID 10797000. Retrieved 21 March 2018.
  19. ^ Descamps, P. (2015). "Dumb-bell-shaped equilibrium figures for fiducial contact binary asteroids and EKBOs". Icarus. 245: 64–79. arXiv:1410.7962. Bibcode:2015Icar..245...64D. doi:10.1016/j.icarus.2014.08.002. S2CID 119272485.
  20. ^ a b c d e f F. Marchis, B. Yang (September 2021). "(216) Kleopatra, a low density critically rotating M-type asteroid". Astronomy & Astrophysics. Retrieved 13 October 2021.
  21. ^ David W. Dunham, Sichao (1991). "The sizes and shapes of (4) Vesta, (216) Kleopatra and (381) Myrrha from observations of occultations during January 1991". Asteroids. International Conference on Asteroids, Comets, Meteors 1991. 765: 54. Bibcode:1991LPICo.765...54D. Retrieved 13 October 2021.
  22. ^ Marchis, F. (13 November 1999). "(216) Kleopatra". Central Bureau for Astronomical Telegrams. Retrieved 21 March 2018.
  23. ^ Hanuš, J.; et al. (2017). "Volumes and bulk densities of forty asteroids from ADAM shape modeling". Astronomy and Astrophysics. 601: 41. arXiv:1702.01996. Bibcode:2017A&A...601A.114H. doi:10.1051/0004-6361/201629956. S2CID 119432730.
  24. ^ Gradie, J.; Flynn, L. (March 1988). "A Search for Satellites and Dust Belts Around Asteroids: Negative Results". Abstracts of the Lunar and Planetary Science Conference. 19: 405–406. Bibcode:1988LPI....19..405G. Retrieved 21 March 2018.
  25. ^ Marchis, Franck (2 October 2008). "Two Companions Found Near Dog-bone Asteroid". Space.com. Retrieved 20 March 2018.
  26. ^ a b M. Broz, B. Yang (September 2021). "An advanced multipole model for (216) Kleopatra triple system". Astronomy & Astrophysics. Retrieved 13 October 2021.

External links[]