216 Kleopatra is a large
M-type asteroid
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere.
...
with a mean diameter of and is noted for its elongate bone or dumbbell shape.
It was discovered on 10 April 1880 by Austrian astronomer
Johann Palisa
Johann Palisa (6 December 1848 – 2 May 1925) was an Austrian astronomer, born in Troppau, Austrian Silesia, now Czech Republic. He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 Gel ...
at the Austrian Naval
Pola Observatory, in what is now
Pula
Pula (; also known as Pola, it, Pola , hu, Pòla, Venetian language, Venetian; ''Pola''; Istriot language, Istriot: ''Puola'', Slovene language, Slovene: ''Pulj'') is the largest city in Istria County, Croatia, and the List of cities and town ...
, Croatia, and was named after
Cleopatra
Cleopatra VII Philopator ( grc-gre, Κλεοπάτρα Φιλοπάτωρ}, "Cleopatra the father-beloved"; 69 BC10 August 30 BC) was Queen of the Ptolemaic Kingdom of Egypt from 51 to 30 BC, and its last active ruler.She was also a ...
, the famous Egyptian queen.
It has two small
minor-planet moon
A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. , there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons (and binary objects, in general) are importan ...
s which were discovered in 2008 and later named Alexhelios and Cleoselene.
Orbit and classification
''Kleopatra'' is a non-
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
asteroid from the main belt's
background population.
It orbits the Sun in the
central
Central is an adjective usually referring to being in the center of some place or (mathematical) object.
Central may also refer to:
Directions and generalised locations
* Central Africa, a region in the centre of Africa continent, also known as ...
asteroid belt at a distance of 2.1–3.5
AU once every 4 years and 8 months (1,706 days;
semi-major axis
In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...
of 2.79 AU). Its orbit has an
eccentricity
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-Centre (geometry), center, in geometry
* Eccentricity (g ...
of 0.25 and an
inclination
Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...
of 13
° with respect to the
ecliptic
The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...
.
The body's
observation arc
In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...
begins at Leipzig Observatory on 20 April 1880, ten days after to its official discovery observation at Pola Observatory.
:
Physical characteristics
Size and Shape
Kleopatra is a relatively large asteroid, with a mean (volume-equivalent) diameter of
and an unusually elongate shape.
The initial mapping of its elongated shape was indicated by stellar occultation observations from eight distinct locations on 19 January 1991.
Subsequent observations with the
ESO 3.6 m Telescope
The ESO 3.6 m Telescope is an optical reflecting telescope run by the European Southern Observatory at La Silla Observatory, Chile since 1977, with a clear aperture of about and area.
The telescopes uses the HARPS instrument and has discovered ...
at
La Silla La Silla may refer to:
* La Silla Observatory, an astronomical observatory in Chile
* Cerro de la Silla, a mountain and natural monument located within the metropolitan area of the city of Monterrey, Nuevo León, in northeastern Mexico.
* La Sill ...
, run by the
European Southern Observatory
The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...
, were interpreted to show a double source with two distinct lobes of similar size.
These results were disputed when radar observations at the
Arecibo Observatory
The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science F ...
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.
Later models suggested that Kleopatra was more elongate and the most recent models using
radar delay-Doppler imaging,
adaptive optics
Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...
, and
stellar occultations provide dimensions of 267 × 61 × 48 km.
Moons
In 1988 a search for satellites or dust orbiting this asteroid was performed using the
UH88
The University of Hawai'i 88-inch (2.24-meter) telescope—called UH88, UH2.2, or simply 88 by members of the local astronomical community—is situated at the Mauna Kea Observatories and operated by the University's Institute for Astronomy. It ...
telescope at the
Mauna Kea Observatories
The Mauna Kea Observatories (MKO) are a group of independent astronomical research facilities and large telescope observatories that are located at the summit of Mauna Kea on the Big Island of Hawaiʻi, United States. The facilities are located ...
, but the effort came up empty.
In September 2008,
Franck Marchis
Franck Marchis (born April 6, 1973 in Caen, France), astronomer and planetary scientist, is best known for his discovery and characterization of multiple asteroids, his study of Io volcanism and imaging of exoplanets, planets around other stars ...
and his collaborators announced that by using the
Keck Observatory
The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when comp ...
's
adaptive optics
Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...
system, they had discovered two
moons
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'' ...
orbiting Kleopatra.
In February 2011, the
minor-planet moon
A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. , there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons (and binary objects, in general) are importan ...
s were named Alexhelios (outer) and Cleoselene (inner), after Cleopatra's children
Alexander Helios and
Cleopatra Selene II
Cleopatra Selene II (Greek: Κλεοπάτρα Σελήνη; summer 40 BC – BC; the numeration is modern) was a Ptolemaic princess, Queen of Numidia (briefly in 25 BC) and Mauretania (25 BC – 5 BC) and Queen of Cyrenaica (34 BC – 30 BC). S ...
.
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.
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.
The most recent adaptive-optics observations and modeling provides a mass of Kleopatra of , or , which is significantly lower than previously thought.
When combined with the best volume estimate for Kleopatra, this indicates a bulk density of .
These recent bulk density results call into question the canonical view of Kleopatra as a pure metallic object.
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.
One way to reconcile these observations is to hypothesize that Kleopatra is a
rubble-pile asteroid with significant porosity in dynamic equilibrium.
Origin
![Size comparison of asteroid Kleopatra with northern Italy](https://upload.wikimedia.org/wikipedia/commons/f/f1/Size_comparison_of_asteroid_Kleopatra_with_northern_Italy.jpg)
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
In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overconta ...
– if it were spinning much faster, the two lobes would separate from each other, making a true binary system.
See also
*
List of exceptional asteroids
The following is a collection of lists of asteroids of the Solar System that are exceptional in some way, such as their size or orbit. For the purposes of this article, "asteroid" refers to minor planets out to the orbit of Neptune, and includes ...
References
External links
Lightcurve plot of 216 Kleopatra Palmer Divide Observatory,
B. D. Warner (2006)
Triplicity and physical characteristics of Asteroid (216) Kleopatra– NASA article, May 2000
An Asteroid for the Dogs August 2000
Dictionary of Minor Planet Names Google books
– Minor Planet Center
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Discoveries by Johann Palisa
Named minor planets
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