Daphnis (moon)
 Daphnis appears as a small dot that causes ripples on the edges of the Keeler Gap in this image from the Cassini probe. | |
| Discovery | |
|---|---|
| Discovered by | Cassini Imaging Science Team |
| Discovery date | May 6, 2005 |
| Designations | |
| Adjectives | Daphnidian |
| Orbital characteristics[1] | |
Mean orbit radius | 136,505.5±0.1 km |
| Eccentricity | 0.0000331 ± 0.0000062 |
| 0.5940798 days (14.257915 hours) | |
| Inclination | 0.0036° ± 0.0013° |
| Satellite of | Saturn |
| Physical characteristics | |
| Dimensions | 9 × 9 × 6 km[2] |
| 3.9 ± 0.8 km[2] | |
| Mass | 8.4 ± 1.2 ×1013 kg[2] |
Mean density | 0.34 ± 0.21 g/cm³[2] |
| unknown | |
| synchronous | |
| unknown | |
| Albedo | ≈ 0.5 |
| Temperature | ~78 K |
Daphnis (Template:PronEng DAF-nis, or as Greek Δαφνίς) is an inner satellite of Saturn. It is also known as Saturn XXXV; its provisional designation was S/2005 S 1.[3][4] Daphnis is about 8 kilometres in diameter, and orbits the planet in the Keeler Gap within the A ring.
Naming
It was named in 2006 after Daphnis, a shepherd, pipes player, and pastoral poet in Greek mythology.[5] He was the son of Hermes, brother of Pan, and descendant of the Titans. Both Pan and Daphnis, the only two known shepherd moons orbiting within Saturn's main rings, are named for mythological figures associated with shepherds.
Discovery
It was discovered by the Cassini Imaging Science Team on May 6, 2005.[3] The discovery images were taken by the Cassini probe over 16 min on May 1, 2005 from a time-lapse sequence of 0.180 second narrow-angle-camera exposures of the outer edge of the A ring. It was subsequently found in 32 low-phase images taken of the F ring on April 13, 2005 (spanning 18 min) and again in two high-resolution (3.54 km/pixel) low-phase images taken on May 2, 2005 when its 7 km disk was resolved. It had previously been inferred from gravitational ripples observed on the outer edge of the Keeler gap. This moon seems to make waves inside the ring.
Orbit
The inclination and eccentricity of Daphnis's orbit are very small, but distinguishable from zero. Daphnis' eccentricity causes its distance from Saturn to vary by ~9 km, and its inclination causes it to move up and down by ~17 km. The Keeler Gap, within which Daphnis orbits, is about 42 km wide.
References
- ^ Jacobson, R. A.; et al. (2008). "Revised orbits of Saturn's small inner satellites". Astronomical Journal. 135: 261–263. doi:10.1088/0004-6256/135/1/261.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ a b c d Porco, C. C.; et al. (2007). "Saturn's Small Inner Satellites: Clues to Their Origins". Science. 318: 1602–1607. doi:10.1126/science.1143977.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ a b C.C. Porco, et al., IAUC 8524: S/2005 S 1 May 6, 2005 (discovery)
- ^ Martinez, C.; and Dyches, P.; Cassini-Huygens: Cassini Finds New Saturn Moon That Makes Waves May 10, 2005
- ^ IAUC 8730: Saturn XXXV (Daphnis) (naming the moon)
External links
- CICLOPS imaging: includes a movie of the moon's ripple effect
- Rody P.S. Oldenhuis (2005-12-21), "Estimating the density of Saturn's Moon Daphnis via its shepherding effect on Nearby Rings" (PDF), Earth and Planetary Observation letters, 1, retrieved 2009-04-26
{{citation}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) shows mathematical treatment and simulation of Daphnis' gravitational wake