Ophelia (moon)
| Ophelia | |
|---|---|
 |
|
| The moons of Ophelia and Cordelia captured by Voyager 2 | |
| Provisional or systematic name | S / 1986 U 8 |
| Central body | Uranus |
| Properties of the orbit | |
| Major semi-axis | 53,763.390 ± 0.847 km |
| Periapsis | 53,230.057 km |
| Apoapsis | 54,296.723 km |
| eccentricity | 0.00992 ± 0.000107 |
| Orbit inclination | 0.10362 ± 0.055 (equatorial plane) ° |
| Orbital time | 0.37640039 ± 0.00000357 d |
| Mean orbital velocity | 10.3873 km / s |
| Physical Properties | |
| Albedo | 0.08 ± 0.01 |
| Apparent brightness | 23.26 ± 0.25 mag |
| Medium diameter | 42.8 ± 8 (54 × 38 × 38) km |
| Dimensions | ≈ 5.3952 10 16 kg |
| surface | ~ 6,600 km 2 |
| Medium density | ≈ 1.3 g / cm 3 |
| Acceleration of gravity on the surface | ≈ 0.0082 m / s 2 |
| Escape speed | ≈ 18.5 m / s |
| Surface temperature | ≈ −184 to −209 ° C / 64–89 K |
| discovery | |
| Explorer | |
| Date of discovery | January 20, 1986 |
| Remarks | Physical data relatively imprecise. |
Ophelia (also Uranus VII ) is the second innermost and one of the smaller of the 27 known moons of the planet Uranus .
Discovery and naming
Ophelia was discovered on January 20, 1986 together with Cordelia 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 8 .
For 14 years, Ophelia (like Cordelia) was considered missing. The astronomer Erich Karkoschka examined some images of the Uranus system obtained with the Hubble Space Telescope in 1997. He stacked the electronic recordings on top of each other and compared pixels with pixels until he finally found what he was looking for. Confirmation came from astronomers Richard French of Wellesley College and Philip Nicholson of Cornell University in March 2000.
Ophelia is a female character from William Shakespeare's Hamlet , who was courted by Prince Hamlet for a long time, but was then harshly rejected by the supposedly madman. Out of grief over the death of her father Polonius, who was killed by a mistake by Hamlet, she went mad and drowned herself.
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
Ophelia orbits Uranus in a prograde , almost perfectly circular orbit at a mean distance of around 53,763 km (around 2.104 Uranus radii) from its center, i.e. 28,204 km above its cloud ceiling. The orbital eccentricity is 0.00992, the web is 0.10362 ° to the equator of Uranus inclined .
The orbit of the innermost moon Cordelia is on average 4,012 km from Cordelia's orbit, that of the nearest outer moon Bianca 5,403 km.
Ophelia is located in the middle of two Uranus rings, the inner ε (epsilon) ring , which is on average around 2,614 km from the Ophelia orbit, and the inner edge of the outer ν (Ny) dust ring at a distance of 12,337 km.
Ophelia moves as the outer shepherd's moon outside the brightest ε-ring of Uranus and influences its ring particles with her gravitational effect. The outer edge of the ring is in a 14:13 orbit resonance to Ophelia , the inner edge in turn has a resonance of 24:25 to the inner shepherd's moon Cordelia. 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.
Ophelia orbits Uranus in 9 hours, 2 minutes and 0.99 seconds. Since this is faster than the rotation of Uranus, Ophelia 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 Ophelia rotates synchronously and that its axis has an inclination of 0 °.
Physical Properties
Ophelia has a mean diameter of 42.8 km. In the recordings of the Voyager-2 - probe Ophelia appeared as an elongate object having dimensions of 54 × 38 × 38 km, wherein the longitudinal axis is aligned with Uranus.
Its mean density of 1.3 g / cm 3 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; That is, 8% of the incident sunlight is reflected from the surface. It is therefore a very dark celestial body. The acceleration due to gravity on its surface is 0.0082 m / s 2 , which is less than 1 ‰ of that on earth. The mean surface temperature of Ophelia is estimated to be between −184 and −209 ° C (89 to 64 K ).
Otherwise, not much is known about this moon, as the probe images were taken at a great distance and therefore have too low a resolution.
exploration
Since the Voyager 2 space probe's flyby, the Uranus system has been studied intensively by both Earth-based observations and the Hubble Space Telescope . The orbit parameters of Ophelia could be specified more precisely.
Web links
- IAUC 4168: Satellites and Rings of Uranus Jan 27, 1986 (discovery)
- IAUC 8194: Satellites of Uranus September 3, 2003 (rediscovery)
- IAUC 8648: Satellites of Uranus December 29, 2005 (numbering and naming)
- Polish moon page: Ophelia description and further links (English)
- Satellite Viewer Orbit simulation of the Uranus moons