Planetary Rings Rings around planets are important to

Planetary Rings • Rings around planets are important to understand because they allow us to test theories about the formation of the solar system. • The early solar system was a disk-shaped nebula around a protostar, and it very likely had some of the features that we see today in the rings of the Jovian planets. • The capture of ring material by shepherd moons, or the clearing of gaps in the rings, are critically important to the accretion process that formed large objects in the solar system nebula.

Saturn’s Rings, seen from Earth

Saturn’s tilt means that we see the rings at different angles over a period of time.

Saturn over four years of observation.

The Roche Limit is the radius at which a moon will fragment into pieces due to the tidal force and form the fragments that make up a ring.

Jovian Ring Systems are inside the Roche limit

Rings of the Jovians, with inner moons shown as dots

Saturn’s Rings, with “Earth” shown for scale.

Saturn’s Rings, as seen in visible light and by occultation of radio waves from the orbiter.

Saturn’s Rings, first half of full image.

Saturn’s Rings, second half of full image.

Saturn’s Rings, first quarter of full image.

Saturn’s Rings, second quarter of full image.

Saturn’s Rings, third quarter of full image.

Saturn’s Rings, fourth quarter of full image.

Saturn’s Rings have very fine structure, like these ripples seen in just a small portion of the rings.

Shepherd moons control the dynamics of parts of the ring.

Pandora, a small moon, may be a shepherd moon for the thin and twisted F ring, the outermost ring around Saturn. There has been some debate about this recently.

Another shepherd moon is in the Encke gap in the rings around Saturn. This shepherd moon is inside the gap and influences the edges of the rings on either side of the gap.

The Encke gap in the rings, showing a twisted thin ring in the gap.

The Encke gap in the rings. Notice the spiral structure on the inner edge.

A shepherd moon causing waves in the edges of the Keeler gap in the rings of Saturn.

These density waves in the rings of Saturn seem to have a mathematical regularity.

Jupiter’s Faint Ring

Jupiter’s faint Rings were seen again in 2007 by the New Horizons spacecraft on it way to Pluto.

Rings of Uranus top picture shows detail of the outermost ring

More Shepherd Moons were seen around Uranus

Neptune’s Faint Rings

The significance of Rings • Rings around planets are important to understand because they allow us to test theories about the formation of the solar system. • The early solar system was a disk-shaped nebula around a protostar, and it very likely had some of the features that we see today in the rings of the Jovian planets. (It was probably much thinner than the artists drawings!) • The capture of ring material by shepherd moons, or the clearing of gaps in the rings, are critically important to the accretion process that formed large objects in the solar system nebula.

A planetary disk in formation has been seen by ALMA http: //www. almaobservatory. org/press-room/press-releases/771 -revolutionary-almaimage-reveals-planetary-genesis and http: //www. eso. org/public/news/eso 1436/