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Daphnis (moon)
Encyclopedia
Daphnis is an inner satellite
of Saturn
. It is also known as ; its provisional designation was . Daphnis is about 8 kilometres in diameter, and orbits the planet in the Keeler Gap within the A ring.
, a shepherd, pipes player, and pastoral poet in Greek
mythology
; he was descendant of the Titans
, after whom the largest moons of Saturn are named. Both Daphnis and Pan
, the only other known shepherd moon to orbit within Saturn's main rings, are named for mythological figures associated with shepherd
s.
Daphnis was discovered by the Cassini Imaging Science Team on May 6, 2005. 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. The moon 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.
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.
Inner satellite
In astronomy, an inner moon is a natural satellite following a prograde, low inclination orbit inwards of the large satellites of the parent planet. They are generally thought to have been formed in situ at the same time as the coalescence of the original planet...
of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
. It is also known as ; its provisional designation was . Daphnis is about 8 kilometres in diameter, and orbits the planet in the Keeler Gap within the A ring.
Naming
The moon was named in 2006 after DaphnisDaphnis
In Greek mythology, Daphnis was a son of Hermes and a Sicilian nymph. A shepherd and flautist, he was the inventor of pastoral poetry. A naiad fell in love with him, but he was not faithful to her. In revenge, she either blinded him or turned him to stone...
, a shepherd, pipes player, and pastoral poet in Greek
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
mythology
Mythology
The term mythology can refer either to the study of myths, or to a body or collection of myths. As examples, comparative mythology is the study of connections between myths from different cultures, whereas Greek mythology is the body of myths from ancient Greece...
; he was descendant of the Titans
Titan (mythology)
In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, that ruled during the legendary Golden Age....
, after whom the largest moons of Saturn are named. Both Daphnis and Pan
Pan (moon)
Pan is the innermost moon of Saturn. It is a walnut-shaped small moon about 35 kilometres across and 23 km high that orbits within the Encke Gap in Saturn's A Ring. Pan acts as a ring shepherd and is responsible for keeping the Encke Gap free of ring particles.It was discovered by Mark R...
, the only other known shepherd moon to orbit within Saturn's main rings, are named for mythological figures associated with shepherd
Shepherd
A shepherd is a person who tends, feeds or guards flocks of sheep.- Origins :Shepherding is one of the oldest occupations, beginning some 6,000 years ago in Asia Minor. Sheep were kept for their milk, meat and especially their wool...
s.
Discovery
Before it was photographed, the existence of a moon in Daphnis's position had already been inferred from gravitational ripples observed on the outer edge of the Keeler gap. The waves made by the moon in the inner edge of the gap precede it in orbit, while those on the outer edge lag behind it, due to the differences in relative orbital speed.Daphnis was discovered by the Cassini Imaging Science Team on May 6, 2005. The discovery images were taken by the Cassini
Cassini-Huygens
Cassini–Huygens is a joint NASA/ESA/ASI spacecraft mission studying the planet Saturn and its many natural satellites since 2004. Launched in 1997 after nearly two decades of gestation, it includes a Saturn orbiter and an atmospheric probe/lander for the moon Titan, although it has also returned...
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. The moon 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
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
) low-phase images taken on May 2, 2005, when its 7 km disk was resolved.
Orbit
The inclinationInclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
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.