Cordelia (moon)
| Cordelia | |
|---|---|
|
|
| Cordelia captured by Voyager 2 | |
| Provisional or systematic name | S / 1986 U 7 |
| Central body | Uranus |
| Properties of the orbit | |
| Major semi-axis | 49,751.722 ± 0.149 km |
| Periapsis | 49,738.787 km |
| Apoapsis | 49,764.657 km |
| eccentricity | 0.00026 ± 0.000096 |
| Orbit inclination | 0.08479 ± 0.031 (equatorial plane) ° |
| Orbital time | 0.33503384 ± 0.00000058 d |
| Mean orbital velocity | 10.7991 km / s |
| Physical Properties | |
| Albedo | 0.08 ± 0.01 |
| Apparent brightness | 23.62 ± 0.35 mag |
| Medium diameter | 40.2 ± 6 (50 × 36 × 36) km |
| Dimensions | ≈ 4.4960 · 10 16 kg |
| surface | ~ 5,500 km 2 |
| Medium density | ≈ 1.3 g / cm 3 |
| Acceleration of gravity on the surface | ≈ 0.0073 m / s 2 |
| Escape speed | ≈ 17.0 m / s |
| Surface temperature | ≈ −184 to −209 ° C / 64–89 K |
| discovery | |
| Explorer | |
| Date of discovery | January 20, 1986 |
| Remarks | Physical data relatively imprecise. |
Cordelia (also Uranus VI ) is the innermost and one of the smaller of the 27 known moons of the planet Uranus .
Discovery and naming
Cordelia was discovered on January 20, 1986 together with Ophelia by the astronomer Richard John Terrile on photographs taken by the Voyager 2 space probe . The discovery was announced on January 27, 1986 by the International Astronomical Union (IAU); the moon was initially given the provisional designation S / 1986 U 7 .
Like Ophelia, Cordelia was lost in the period that followed. Astronomers Richard French from Wellesley College and Philip Nicholson from Cornell University looked for wave-like distortions in the shape of the Uranus rings that could be caused by the gravitational effects of these shepherd moons . The scientists found a wave-like pattern on one edge of the epsilon ring. Assuming that this ripple would have to be in accordance with the orbital movements of Cordelia and Ophelia, they calculated their location. The calculated position for Ophelia was very close to where Erich Karkoschka (Lunar and Planetary Laboratory, Tucson) had found Ophelia. French and Nicholson then provided Karkoschka with a position for Cordelia. And when Karkoschka checked the Hubble images in March 2000, he found Cordelia exactly where French had predicted. The two moons were found again.
Cordelia (Latin for "the right heart") is the king's youngest daughter in William Shakespeare's tragedy King Lear , who has a noble heart and loves her father selflessly and sincerely.
All the moons of Uranus are named after characters from Shakespeare or Alexander Pope . The first four Uranus moons discovered ( Oberon , Titania , Ariel , Umbriel ) were named after suggestions by John Herschel , the son of the Uranus discoverer Wilhelm Herschel . Later the tradition of naming was retained.
Track properties
Orbit
Cordelia orbits Uranus in a prograde , almost perfectly circular orbit with an average distance of around 49,752 km from its center, i.e. 24,193 km above its cloud ceiling. This means that it is closer to the surface than the Uranus Uranus center itself. The orbital eccentricity is 0.00026, the web is 0.08479 ° to the equator of Uranus inclined .
The orbit of the nearest outer moon Ophelia is on average 4012 km from Cordelia's orbit. Cordelia is located in the middle of two Uranus rings, the inner δ (delta) ring , which is on average around 1452 km from the Cordelia orbit, and the outer λ (lambda) dust ring only 271 km away.
Cordelia moves as an inner shepherd's moon within the brightest ε (epsilon) ring of Uranus, which is 1397 km away from the Cordelia orbit, and influences its ring particles with its gravitational effect. The inner edge of the ring is in a 24:25 orbit resonance to Cordelia , the outer edge in turn has a resonance of 14:13 to the outer shepherd's moon Ophelia. The masses of the two moons must be at least three times the mass of the ring so that it can be effectively kept within its confines. The mass of the ε-ring is estimated at around 10 16 kg. In addition, the sharp outer edge of the δ ring has a 23:22 resonance with Cordelia.
Cordelia orbits Uranus in 8 hours, 2 minutes and 26.92 seconds. Since this is faster than the rotation of Uranus, Cordelia rises in the west and sets in the east as seen from Uranus.
It moves within a critical distance, near the Roche limit , in a descending orbit around the planet and will at some point be torn apart as a result of tidal forces into a ring or fall or burn up in Uranus' atmosphere.
rotation
It is believed that Cordelia rotates synchronously and that its axis is inclined at 0 °.
Physical Properties
Cordelia has a mean diameter of 25 miles. In the images taken by the Voyager 2 spacecraft , Cordelia appeared as an elongated object measuring 50 × 36 × 36 km, with the long axis aligned with Uranus.
At 1.3 g / cm³, its mean density is significantly lower than the density of the earth and indicates that the moon is mainly composed of water ice.
It has a very low albedo of 0.08, which means that 8% of the incident sunlight is reflected from the surface. It is therefore a very dark celestial body.
On its surface, the acceleration due to gravity is 0.0073 m / s², which corresponds to less than 1 ‰ of that on earth.
The mean surface temperature of Cordelia is estimated to be between −184 and −209 ° C (89–64 K ).
Otherwise, not much is known about this moon, as the probe images were taken at a great distance and therefore have a low resolution.
exploration
Since Voyager 2's flyby, the Uranus system has been studied extensively by both Earth-based observations and the Hubble Space Telescope . The orbit parameters of Cordelia could be specified more precisely.
Web links
- IAUC 4168: Satellites and Rings of Uranus Jan 27, 1986 (discovery)
- IAUC 4609: Satellites of Saturn and Uranus June 8, 1988 (numbering and naming)
- Polish moon page: Cordelia - description and further links (English)
- Satellite Viewer - orbit simulation of Uranus' moons