Hyperion (moon)
| Hyperion | |
|---|---|
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| Saturn moon Hyperion in false colors , taken by Cassini | |
| Central body | Saturn |
| Properties of the orbit | |
| Major semi-axis | 1,464,100 km |
| Periapsis | 1,438,480 km |
| Apoapsis | 1,489,700 km |
| eccentricity | 0.0175 |
| Orbit inclination | 0.568 ° |
| Orbital time | 21.28 d |
| Mean orbital velocity | 5.00 km / s |
| Physical Properties | |
| Albedo | 0.25 |
| Apparent brightness | 14.2 mag |
| Medium diameter | 360 × 280 × 225 (266) km |
| Dimensions | 0.56199 × 10 19 ± 0.05 kg |
| surface | 230,000 km 2 |
| Medium density | 0.544 ± 0.050 g / cm 3 |
| Sidereal rotation | chaotic |
| Axis inclination | 0 ° to 180 ° |
| Acceleration of gravity on the surface | 0.041 m / s 2 |
| Escape speed | 101 m / s |
| discovery | |
| Explorer |
WC Bond , |
| Date of discovery | September 16, 1848 |
Hyperion (also Saturn VII ) is one of the medium-sized moons of Saturn . It has a very porous, sponge-like structure.
discovery
Hyperion was discovered by William Cranch Bond , George Phillips Bond and William Lassell on September 16, 1848 .
The moon was named after the titan Hyperion from Greek mythology .
Hyperion was discovered shortly after a publication by the astronomer John Herschel ( Results of Astronomical Observations made at the Cape of Good Hope ) in 1847 , in which he suggested the names of the seven moons of Saturn known up to that point. Lassell, who spotted Hyperion two days after the Bonds, was familiar with Herschel's naming scheme. Based on this, he suggested the name Hyperion.
Orbit data
Hyperion orbits Saturn at a mean distance of 1,464,100 km in 21 days, 6 hours and 43 minutes. The orbit has an eccentricity of 0.0175 and is inclined 0.568 ° to the equatorial plane of Saturn.
Structure and physical data
For its size, Hyperion is one of the most irregularly shaped bodies in the solar system . It has an area of 360 × 280 × 225 km.
Apparently Hyperion is a fragment of a larger original body that broke during an impact event . On its surface, the huge, 10 km deep Helios crater with a diameter of 120 km is visible.
Like most of Saturn's moons, Hyperion has a very low density of 0.544 g / cm 3 . It is evidently composed predominantly of porous water ice with a small amount of silicate rock. This gives it a spongy appearance with very low gravity on the surface.
As a result, impact bodies tend to compress the surface rather than push material aside. Most of the material that is thrown into the air never returns because of the low gravity.
In contrast to most of Saturn's moons, Hyperion has a dark surface with an albedo of 0.25, which could result from the deposition of a dark material. According to investigations by the Cassini spacecraft in 2005, the dark deposits are hydrocarbon compounds . After the discovery and investigation of the Phoebe ring , Phoebe is believed to be the cause of the darkening.
Hyperion's surface is covered in deep, sharp-edged craters that give it the appearance of a giant sponge. The bottom of the crater is filled with dark material. Reddish material contains long hydrocarbon chains and is apparently similar to the material of other Saturn moons, particularly Iapetus .
The latest analysis of Cassini's data during his Flybys at Hyperion in 2005 and 2006 shows that the porosity is so high that about 40 percent of its interior is empty. This porosity allows craters to remain virtually unchanged for eons.
There is a named rock ridge ( Dorsum , English: Ridge) on Hyperion: Bond-Lassell Dorsum (48 ° N 143.5 ° W, on the edge of the Helios crater), named after George Phillips Bond, William Cranch Bond and William Lassell. In addition to this large impact crater, there are three other named smaller ones (Bahloo, Jarilo and Meri).
rotation
Recordings from the Voyager 2 spacecraft and terrestrial photometric surveys showed that Hyperion's rotation is chaotic , with its axis of rotation and speed fluctuating in completely unpredictable ways. Along with Pluto's moons Nix and Hydra , it is the third known moon in the solar system to exhibit this behavior, although computer simulations have shown that other irregularly shaped moons may have rotated in this way in the past.
Hyperion occupies a special position among the moons. It is highly irregular in shape, its orbit is eccentric and it is located at a relatively short distance from a large moon, Titan , with which it moves in a 3: 4 resonance around the planet. These factors limit the ways in which stable rotation is possible.
Observation and approximation
Hyperion is a faint object with an apparent magnitude of 14.2 m . A larger telescope is required to observe it .
On July 11, 2005, the Cassini space probe was able to send new images of the moon from a distance of some 10,000 km from Earth while it was flying past.
On September 26, 2005, the same probe examined the moon more closely during another flyby, during which it came extremely close to only 500 km away. The best images of the moon so far were taken, showing an unusual surface and supporting the assumption of a relatively porous consistency.
For the third and last time, the probe examined the Hyperion on May 31, 2015, when it approached it to a minimum of 34,000 km. Cassini made further recordings.
Others
On its orbit, Hyperion repeatedly steps out of Saturn's magnetosphere into the area of influence of the solar wind and then back again. Due to the changing radiation conditions, it charges itself electrically.
Web links
- Hyperion at Monde.de
- The nine planets: Hyperion
- MNRAS 9 (1848) 1: Discovery of a new satellite of Saturn (Bond)
- MNRAS 8 (1848) 195: Discovery of a new satellite of Saturn (Lassell)
- Report on the Hyperion flyby on 7 July 2005 (English)
- Film from the flyby of the Cassini probe on July 7, 2005 (QuickTime video; 875 kB)
- Film from the extremely close flyby on September 26, 2005 (QuickTime video; 14.2 MB)
Individual evidence
- ↑ http://www.ciclops.org/media/sp/2011/6794_16344_0.pdf
- ↑ http://www.ciclops.org/media/sp/2011/6794_16344_0.pdf
- ↑ Published in Nature July 5, 2007.
- ^ Cassini Prepares for Last Up-close Look at Hyperion . In: Jet Propulsion Laboratory , May 28, 2015. Retrieved September 20, 2017.
- ↑ Key to Giant Space Sponge Revealed . In: Space.com . Retrieved September 20, 2017.
- ↑ www.unmannedspaceflight.com: Hyperion with graphic Hyperion: Named craters
- ↑ Hyperion at Monde.de
- ^ FAZ October 5, 2005, p. N1.
- ↑ Archived copy ( memento of the original from June 26, 2015 in the Internet Archive ) 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. NASA Jet Propulsion Laboratory: Cassini Sends Final Close Views of Odd Moon Hyperion , Date: June 2. 2015. Accessed June 25, 2015
- ↑ Ralph-Mirko Richter: Saturn moon Hyperion is electrostatically charged, in raumfahrer.net , date: October 18, 2014, accessed: January 16, 2015
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Semi- major axis (km) Hyperion 1.464.100 |
Iapetus |