(216) Cleopatra
|
Asteroid (216) Cleopatra |
|
|---|---|
|
|
| Radar astronomical model by Cleopatra | |
| Properties of the orbit ( animation ) | |
| Orbit type | Middle main belt |
| Major semi-axis | 2.7936 AU |
| eccentricity | 0.2508 |
| Perihelion - aphelion | 2.0930 AU - 3.4943 AU |
| Inclination of the orbit plane | 13.113 ° |
| Length of the ascending node | 215.359 ° |
| Argument of the periapsis | 180.136 ° |
| Time of passage of the perihelion | May 27, 2018 |
| Sidereal period | 4 a 245.5 d |
| Mean orbital velocity | 17.5 km / s |
| Physical Properties | |
| Medium diameter | 121.6 ± 1.6 km |
| Dimensions | 219.04 × 93.64 × 83.76 km |
| Dimensions | 4.64 ± 0.02 x 10 18 kg |
| Albedo | 0.1164 ± 0.0040 |
| Medium density | 3.6 ± 0.4 g / cm³ |
| Rotation period | 5 h 23 min 7 s |
| Absolute brightness | 7.3 likes |
| Spectral class | M. |
| history | |
| Explorer | Johann Palisa |
| Date of discovery | April 10, 1880 |
| Another name | A905 OA, A910 RA |
| Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items. | |
(216) Cleopatra is one of the largest asteroids in the main asteroid belt . With a mean diameter of 122 km, Cleopatra is one of the larger asteroids in the main belt. Cleopatra has two moons : Alexhelios and Cleoselene with diameters of about 9 and 7 km respectively.
Discovery and naming
Cleopatra was discovered on April 10, 1880 by the Austrian astronomer Johann Palisa at the Pula Observatory in Pula , Croatia .
The heavenly body was named after the ancient Egyptian ruler Cleopatra , the last queen in ancient Egypt .
In total, the asteroid was observed through several earth-based telescopes, a total of 2,729 times within 137 years. (As of Sept. 2017)
Track properties
Orbit
Cleopatra orbits the sun in a prograde , elliptical orbit between 313,110,000 km (2.09 AU ) and 522,730,000 km (3.49 AU) from its center. The orbit eccentricity is 0.251, the orbit is inclined 13.1 ° to the ecliptic . Its orbit is therefore in the middle asteroid belt .
The period of orbit of Cleopatra is 4.67 years.
rotation
Cleopatra rotates once around its axis in 5 hours, 23 minutes and 7 seconds. From this it follows that the asteroid performs 7,600.8 self- rotations ("days") in a Cleopatra year .
Physical Properties
Size and shape
The most precise determination of the diameter ( geometric mean ) is 121.55 km. Cleopatra has an unusual shape; it is a so-called "contact binary". With regard to the exact dimensions, the most precise value is 219.04 × 93.64 × 83.76 km, so Cleopatra is far more than twice as long as it is wide. The original findings with the ESO 3.6 m telescope in La Silla showed two separate bodies of similar size, as is the case with (90) Antiope / S / 2000 (90) 1 . However, radar observations at the Arecibo Observatory in Puerto Rico have shown that Cleopatra is instead an irregular celestial body with two connected components, the elongated shape of which is reminiscent of a dog's bone. However, if Cleopatra were to turn even faster, the two components would separate from each other and form a real double system.
Assuming a mean diameter of 121.6 km, the surface area is 46,400 km 2 , which is slightly larger than the area of Estonia .
| year | Dimensions km | source |
|---|---|---|
| 2000 | 217 × 94 × 81 ± 25 | Ostro et al. |
| 2001 | 124 | Yeoman ( JPL ) |
| 2004 | 135.07 ± 2.10 | Tedesco (IRAS) et al. |
| 2006 | 104.30 | Shevchenko (IRAS) et al. |
| 2011 | 121.55 ± 1.60 | Usui et al. |
| 2011 | 138.00 ± 19.37 | Mainzer et al. |
| 2012 | 137.794 | Pravec et al. |
| 2012 | 102.93 ± 3.81 | Masiero et al. |
| 2016 | 219.04 x 93.64 x 83.76 | Yu |
The most precise determination is marked in bold .
internal structure
Due to the strong reflection of the radio waves, it is concluded that Cleopatra is a differentiated asteroid with an iron - nickel core, a silicate mantle and a silicate crust. The outer surface is possibly made up of the mineral enstatite , a material from which a group of stone meteorites ( enstatite chondrite ) is also made.
Cleopatra belongs to the M-type asteroids (according to another classification: Xe) with an albedo of 0.116. The density is 3.6 g / cm 3 and is unusually low for a metallic asteroid; this should actually be between 5 and 7 g / cm 3 . Calculations of the radar albedo and the orbits of the moons show that it is not a compact body, but is probably a rubble pile , a collection of metals, dust and rocks, which is riddled with cavities. The porosity is estimated to be 30-50%.
According to calculations, it is likely that the asteroid formed from debris from a previous collision that occurred before the moons were formed perhaps 100 million years ago. According to this, the increased speed of rotation would have lengthened the asteroid and removed the first moon Alexhelios. Cleoselene separated from Cleopatra much later, only about 10 million years ago.
Based on the density of 3.6 g / cm³ and the discovery of the two moons, the mass could so far be calculated to be 4.6 ∙ 10 18 .
The mean surface temperature is around 166 K (−107 ° C).
The Cleopatra Triple System
As early as 1993 Cleopatra was looking for companions without success. Finally, on September 19, 2008, two small moons were discovered using adaptive optics with the Keck Telescope II . In February these were named after the two children of Cleopatra and Marcus Antonius , Alexander Helios and Cleopatra Selene : Alexhelios and Cleoselene .
The first moon Alexhelios, initially designated as S / 2008 (216) 1 , has a diameter of around 9 km and orbits Cleopatra at a distance of 678 km in 2.32 days.
Shortly after Alexhelios, Cleoselene was identified on the same day as another companion, which was initially given the designation S / 2008 (216) 2 . Cleoselene orbits Cleopatra within the orbit of the outer Alexhelios and is around 7 km tall; it moves at a distance of 454 km in 1.24 days around the asteroid.
Cleopatra is after (87) Sylvia , (45) Eugenia and (3749) Balam the fourth asteroid multiple system discovered in the main belt. Apart from the dwarf planets Pluto and Haumea - which also have an asteroid number - it is the sixth known multiple asteroid system in the solar system after Sylvia, Eugenia, (47171) Lempo , (153591) 2001 SN 263 and Balam.
The Cleopatra system at a glance:
| Components | Physical parameters | Path parameters | discovery | |||||
|---|---|---|---|---|---|---|---|---|
| Surname | Throughput diameter (km) |
Relative size % |
Mass (kg) |
Major semi-axis (km) |
Orbital time (d) |
eccentricity | Inclination with respect to the ecliptic |
Date of discovery Date of publication |
| (216) Cleopatra | 121.6 | 100.00 | 4.6 · 10 18 | - | - | - | - | April 10, 1880 1880 |
|
Cleoselene (Cleopatra II) |
6.9 | 5.7 | ? | 454 | 1.24 | 0.00 | 49.0 | September 19, 2008 September 24, 2008 |
|
Alexhelios (Cleopatra I) |
8.9 | 7.3 | ? | 678 | 2.32 | 0.00 | 51.0 | September 19, 2008 September 24, 2008 |
See also
Web links
- Two Companions Found Near Dog-Bone Asteroid . Discovery report with picture of Cleopatra, Cleoselene and Alexhelios (English)
- A dog-bone-shaped asteroid's two moons: Cleopatra, Cleoselene, and Alexhelios . With animation by Cleopatra, Cleoselene and Alexhelios (English)
Individual evidence
- ↑ a b (216) Cleopatra in the Small-Body Database of the Jet Propulsion Laboratory (English).
- ↑ Steven J. Ostro et al .: Radar Observations of Asteroid 216 Cleopatra . May 2000, bibcode : 2000Sci ... 288..836O .
- ^ EF Tedesco et al .: IRAS Minor Planet Survey V6.0 . October 2004 bibcode : 2004PDSS ... 12 ..... T .
- ^ Vasilij G. Shevchenko et al .: Asteroid albedos deduced from stellar occultations . September 2006, bibcode : 2006Icar..184..211S .
- ↑ Fumihiko Usui et al .: Asteroid Catalog Using Akari: AKARI / IRC Mid-Infrared Asteroid Survey . October 2011, bibcode : 2011PASJ ... 63.1117U .
- ^ Amy Mainzer et al .: NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results . November 2011, bibcode : 2011ApJ ... 741 ... 90M .
- ↑ Petr Pravec et al .: Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations . September 2012, bibcode : 2012Icar..221..365P .
- ↑ Joseph R. Masiero et al .: Preliminary Analysis of WISE / NEOWISE 3-Band Cryogenic and Post-Cryogenic Observations of Main Belt Asteroids . September 2012, arxiv : 1209.5794 .
- ↑ Yang Yu: Orbital Dynamics in the Gravitational Field of Small Bodies (2016). Retrieved September 11, 2017 .
- ↑ Jet Propulsion Laboratory : Asteroid 216 Cleopatra ( Memento from April 11, 2009 in the Internet Archive )
- ^ Franck Marchis: Triple Asteroid System (216) Cleopatra (February 2011). Retrieved September 11, 2017 .
- ↑ Space.com: Two Companions Found Near Dog-bone Asteroid
- ↑ MPC 73983. (PDF; 2.2 MB) minorplanetcenter.org
- ^ Daniel WE Green: IAUC No. 8980: S / 2008 (216) 1 and S / 2008 (216) 2 Discovery Publication (September 2008). Retrieved September 11, 2017 .
- ↑ Bin Yang et al .: Elektra: Ein neue Dreifachasteroid (2016). Retrieved September 10, 2017 .