Epimetheus (měsíc)
| Epimetheus | |
|---|---|
 Epimetheus na snímku ze sondy Cassini (2007). | |
| Identifikátory | |
| Typ | měsíc |
| Označení | Saturn XI |
| Objeveno | |
| Datum | 18. prosince 1966 |
| Objevitel | Richard Walker |
| Elementy dráhy (Ekvinokcium J2000,0) | |
| Velká poloosa | 151 410 km |
| Výstřednost | 0,0098 |
| Sklon dráhy | |
| - ke slunečnímu rovníku | 0,351° |
| Mateřská planeta | Saturn |
| Fyzikální charakteristiky | |
| Polární průměr | 117,2 ± 0,6[1] km |
| Hmotnost | (5,25607 ± 0,00081)×1017 kg |
| Průměrná hustota | 0,6233 ± 0,0015[2] g/cm³ |
| Gravitace na rovníku | 0,0066–0,0109[1] m/s² |
| Úniková rychlost | 0,033 km/s |
| Perioda rotace | 0.694333517 dne d |
| Albedo | 0,73 |
| Povrchová teplota | |
| - průměrná | 78 K |
Epimetheus je měsíc planety Saturn. Objeven byl roku 1966 a objevitelem se stal Richard Walker. Byl pojmenován po Titánovi Epiméthovi. Doba jednoho oběhu kolem planety měsíci trvá 0,6942 dne a stejnou dobu potřebuje i měsíc na jednu otáčku kolem vlastní osy. Kolem Saturnu prolétá rychlosti 15,87 km/s. Epimetheus má slabé magnetické pole, které je rovno 15,7 Vo. Epimetheus obíhá kolem Saturnu po téměř identické oběžné dráze jako Janus. Jejich dráhy dělí pouhých 50 km. Jednou za čtyři roky se k sobě natolik přiblíží, že se vnitřní měsíc díky vzájemné přitažlivosti urychlí a putuje na vyšší oběžnou dráhu, vnější měsíc se naopak zpomalí a putuje na nižší oběžnou dráhu.
Galerie
Epimetheus (2016)
Detail povrchu (2017)
Oběžné dráhy Epimethea a Janusu
Interakce Epimethea a Janusu
Epimetheus (níže vlevo) a Janus
Reference
- ↑ a b THOMAS, P., HELFSTEIN, P. The small inner satellites of Saturn: Shapes, structures and some implications. Icarus. 1. 7. 2020, s. 113355. Dostupné online. ISSN 0019-1035. DOI 10.1016/j.icarus.2019.06.016. (anglicky)
- ↑ LAINEY, V., a kolektiv. Characterising the interior of five inner Saturnian moons using Cassini ISS data. Astronomy & Astrophysics. 27. 2023, s. L25. Dostupné online. DOI 10.1051/0004-6361/202244757. (anglicky)
Externí odkazy
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.jpg)
Autor: Kevin Gill from Los Angeles, CA, United States, Licence: CC BY 2.0
Assembled using green and clear filtered images of Epimetheus taken by the Cassini spacecraft on February 21 2017.
NASA/JPL-Caltech/SSI/Kevin M. Gill
Epimetheus The view was obtained at a distance of approximately 2690 kilometers from Saturn Moon. Image scale on Epimetheus is 160 meters per pixel.
(c) Jrkenti na projektu Wikipedie v jazyce angličtina, CC BY-SA 3.0
This is an illustration of the horseshoe orbits of Janus and Epimetheus around Saturn. The dates in this image were taken from "The Rotation of Janus and Epimetheus" by Tiscareno et al. published in Icarus, July 6 2009. The size of Saturn is proportional to the average orbital radius, but the distance from the average radius to the inner/outer radii has been exaggerated 500-fold. The sizes of the moons are exaggerated 50-fold.
In their orbital ballet, Janus and Epimetheus swap positions every four years -- one moon moving closer to Saturn, the other moving farther away. The two recently changed positions (the swap occurring on January 21, 2006), and Janus will remain the innermost of the pair until 2010, when they will switch positions again.
Although the moons appear to be close in the image, they are not. Janus (181 kilometers, or 113 miles across at right) is about 40,000 kilometers (25,000 miles) farther away from Cassini than Epimetheus (116 kilometers, or 72 miles across, at left) in this view. In fact, even when they are at their closest, tugging at each other and swapping orbital positions, they are never closer than about 15,000 kilometers (9,000 miles).
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 20, 2006 at a distance of approximately 452,000 kilometers (281,000 miles) from Epimetheus and 492,000 kilometers (306,000 miles) from Janus. The image scale is 3 kilometers (2 miles) per pixel on both moons.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/home/index.cfm. The Cassini imaging team homepage is at http://ciclops.org.
The NASA image has been cropped.
Autor: Phoenix7777, Licence: CC BY-SA 4.0
Animation of Epimetheus orbit - Rotating reference frame
▇ Saturn · ▇ Janus · ▇ Epimetheus