Jump to content

Daphnis (moon)

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Mike s (talk | contribs) at 22:58, 2 January 2010 (link reference to full journal article). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Daphnis
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 byCassini Imaging Science Team
Discovery dateMay 6, 2005
Designations
AdjectivesDaphnidian
Orbital characteristics[1]
Mean orbit radius
136,505.5±0.1 km
Eccentricity0.0000331 ± 0.0000062
0.5940798 days (14.257915 hours)
Inclination0.0036° ± 0.0013°
Satellite ofSaturn
Physical characteristics
Dimensions9 × 9 × 6 km[2]
3.9 ± 0.8 km[2]
Mass8.4 ± 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.

When Saturn is close to its equinox, shadows cast onto the rings show the vertical relief of waves that Daphnis causes.

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

  1. ^ 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)
  2. ^ 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)
  3. ^ a b C.C. Porco, et al., IAUC 8524: S/2005 S 1 May 6, 2005 (discovery)
  4. ^ Martinez, C.; and Dyches, P.; Cassini-Huygens: Cassini Finds New Saturn Moon That Makes Waves May 10, 2005
  5. ^ IAUC 8730: Saturn XXXV (Daphnis) (naming the moon)