- 216 Kleopatra
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216 Kleopatra 
(Animation)DiscoveryDiscovered by Johann Palisa Discovery date April 10, 1880 DesignationsNamed after Cleopatra VII Alternate name(s) A905 OA, A910 RA Minor planet
categoryMain belt Epoch 30 January 2005 (JD 2453400.5) Aphelion 3.496 AU (523.049 Gm) Perihelion 2.089 AU (312.544 Gm) Semi-major axis 2.793 AU (417.796 Gm) Eccentricity 0.252 Orbital period 4.67 a (1704.704 d) Average orbital speed 17.82 km/s Mean anomaly 55.259° Inclination 13.136° Longitude of ascending node 215.672° Argument of perihelion 179.099° Satellites 2 Physical characteristicsDimensions 217 × 94 × 81 km Mass 4.64 ± 0.02 × 10^18 kg [1] Mean density 3.6 Rotation period 5.385 h Albedo 0.116 Temperature unknown Spectral type M Absolute magnitude (H) 7.3 216 Kleopatra (
/ˌkliːɵˈpætrə/) is a trinary main-belt asteroid that was discovered by Johann Palisa on April 10, 1880, in Pola. It is named after Cleopatra, Queen of Ancient Egypt.Kleopatra has an unusual shape that has been compared to a dog's bone. This bilobate shape was revealed by adaptive optics on the ESO 3.6 m Telescope at La Silla, run by the European Southern Observatory. By bouncing radar signals off the asteroid, a team of astronomers at the Arecibo radio telescope in Puerto Rico were able to develop a more detailed computer model of its shape, which confirmed the earlier results.
Kleopatra is a relatively large asteroid, measuring 217 × 94 × 81 km. Calculations from its radar albedo and the orbits of its moons show it to be a rubble pile, a loose amalgam of metal, rock, and 30–50% empty space by volume, likely due to a disruptive impact prior to the impact that created its moons.
Satellite system
In September 2008, Franck Marchis and his collaborators announced that using the Keck Observatory's adaptive optics system, they had discovered two moons orbiting Kleopatra.[2] The outer and inner satellites are about 5 km and 3 km in diameter, respectively.[3]
In February 2011 they were named Alexhelios (/ˌælɨksˈhiːli.ɵs/, outer) and Cleoselene (/ˌkliːɵsɨˈliːniː/, inner), after Cleopatra's children Alexander Helios and Cleopatra Selene II.[4]It is believed that Kleopatra's odd shape, rotation, and moons are due to 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 around 10 million years ago. Thus Kleopatra may be a failed binary asteroid, very close to being a contact binary.[1]
References
- ^ a b Marchis, Descamps, et al. Icarus, Triplicity and physical characteristics of Asteroid (216) KleopatraFeb. 2011.
- ^ F. Marchis, et al, SETI Institute, UC Berkeley (2008-09-19). "Composite image of (216) Kleopatra observed with the 10m-Keck II telescope". Space.com. http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=081002-seti-dogbone-02.jpg&cap=Composite+image+of+(216)+Kleopatra+observed+with+the+10m-Keck+II+telescope+and+its+adaptive+optics+system+on+September+19+2008+UT.+The+central+dark+circle+shows+the+dog-bone+shape+of+the+primary.+The+arrows+indicate+the+position+of+the+newly+discovered+satellites+with+temporary+names+S/2008+(216)+1+and+S/2008+(216)+2.+Credit:+F.+Marchis,+et+al,+SETI+Institute,+UC+Berkeley. Retrieved 2008-10-02.
- ^ Franck Marchis (Principal Investigator, SETI Institute, UC Berkeley) (2008-09-19). "Two Companions Found Near Dog-Bone Asteroid". SETI Institute. http://www.seti.org/Page.aspx?pid=1182. Retrieved 2009-10-26.
- ^ MPC 73983
- The Asteroid Orbital Elements Database
- Minor Planet Discovery Circumstances
- Asteroid Lightcurve Data File
- Triplicity and physical characteristics of Asteroid (216) Kleopatra
External links
- Bilobated shape of 216 Kleopatra
- Astronomers Catch Images of Giant Metal Dog Bone Asteroid – NASA article
- An Asteroid for the Dogs
- Orbital simulation from JPL (Java) / Ephemeris
Minor planets navigator Small Solar System bodies Minor planets - Designation
- Groups
- Moons
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Comets Meteoroids Lists / categories - Asteroid groups and families
- Asteroid moons
- Binary asteroids
- Minor planets
Categories:- Main Belt asteroids
- M-type asteroids
- Asteroids named for people
- Astronomical objects discovered in 1880
- Discoveries by Johann Palisa
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