Cleoselene
| (216) Cleopatra II (Cleoselene) | |
|---|---|
| Provisional or systematic name | S / 2008 (216) 2 |
| Central body | (216) Cleopatra |
| Properties of the orbit | |
| Major semi-axis | 454 ± 6 km |
| Periapsis | 454 ± 6 km |
| Apoapsis | 454 ± 6 km |
| eccentricity | 0.00 |
| Orbit inclination | 49.0 ° ± 2.0 ° |
| Orbital time | 1.24 ± 0.02 d |
| Physical Properties | |
| Albedo | ≈ 0.1164 ± 0.0040 |
| Medium diameter | 6.9 ± 1.6 km |
| surface | 150 km 2 |
| Medium density | ≈ 3.6 ± 0.4 g / cm 3 |
| Surface temperature | 166 K |
| discovery | |
| Explorer |
|
| Date of discovery | September 19, 2008 |
| Remarks | Smaller moon of the Cleopatra system |
Cleoselene is the inner and smaller of the two moons of the main belt asteroid (216) Cleopatra . Their mean diameter is around 6.9 kilometers, which corresponds to about 1/18 of Cleopatra's mean diameter.
Discovery and naming
Cleoselene was discovered on September 19, 2008 by Franck Marchis, Pascal Descamps, Jérôme Berthier and JP Emery using adaptive optics on the 10 m Keck II telescope on Mauna Kea in Hawaii on the same day shortly after Alexhelios . Cleopatra was at a convenient distance of 1.23 AU from Earth at this time . As early as 1993, a search for companions with the Hubble space telescope was unsuccessful, but Cleopatra was 2.38 AU away at the time. The discovery was announced on September 24, 2008; the moon was given the provisional designation S / 2008 (216) 2 .
The Cleopatra system is after (87) Sylvia , (45) Eugenia and (3749) Balam the fourth asteroid multiple system discovered in the main belt and the sixth overall.
On February 18, 2011, both moons were officially named after the two children of Cleopatra and Marcus Antonius , Cleopatra Selene II and Alexander Helios . In Greek mythology , Selene represents the moon and Helios the sun .
Track properties
Cleoselene orbits Cleopatra on a prograde , elliptical orbit at an average distance of around 454 kilometers from its center (around 7.5 Cleopatra radii). The eccentricity of the orbit is practically circular at 0.00, the orbit inclination is about 49 °. The orbit of the outer moon Alexhelios is on average about 224 km from the orbit of Cleoselene.
Cleoselene orbits Cleopatra in 1 day and 5.8 hours, which corresponds to about 1375.6 orbits in a Cleopatra year (about 4.67 earth years).
Physical Properties
size
Cleoselene has a diameter of 6.9 km, based on the assumed equal reflectivity of 11.6% corresponding to Cleopatra . The surface is therefore relatively dark.
Assuming a mean diameter of 6.9 km, the surface area is around 150 km 2 , which is slightly less than the area of Liechtenstein .
Provisions of the diameter for Cleoselene
| year | Dimensions km | source |
|---|---|---|
| 2008 | 3.0 | Marchis et al. |
| 2010 | 6.9 ± 1.6 | Descamps et al. |
The most precise determination is marked in bold .
internal structure
Since Cleoselene is probably made of the same material as Cleopatra, the density is estimated at 3.6 g / cm 3 as with Cleopatra . It can therefore be assumed that Cleoselene is porous on the inside and, like the mother body, belongs to the Rubble Piles .
The mean surface temperature is around 166 K (−107 ° C).
According to calculations, Cleopatra's strange shape, its rotation and the moon Alexhelios were formed by an oblique impact about 100 million years ago. Accordingly, the increased rotation caused by the impact pulled the mother asteroid into the elongated shape observed today and caused Alexhelios to break off. The breaking off of Cleoselene apparently occurred much later, this event is believed to have occurred 10 million years ago.
See also
Web links
- Two Companions Found Near Dog-Bone Asteroid Discovery Report with picture of Cleopatra, Cleoselene and Alexhelios
- A dog-bone-shaped asteroid's two moons: Cleopatra, Cleoselene, and Alexhelios With animation of Cleopatra, Cleoselene and Alexhelios (English)
Individual evidence
- ^ Daniel WE Green: IAUC No. 8980: S / 2008 (216) 1 and S / 2008 (216) 2 Discovery Publication (September 2008). Retrieved September 11, 2017 .
- ↑ a b Pascal Descamps et al .: Triplicity and Physical Characteristics of Asteroid (216) Cleopatra (PDF). Retrieved September 11, 2017 .
- ^ Franck Marchis et al .: Two Companions Found Near Dog-Bone Asteroid (2006). (No longer available online.) Archived from the original on September 11, 2017 ; accessed on September 11, 2017 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
