Ch' 8 part 4: Rings, Pluto and beyond

1
Ch. 8 part 4 Rings, Pluto and beyond

• 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.

2
Saturns Rings, seen from Earth
3
Saturns tiltmeans that we see the rings at
different anglesover a periodof time.
4
Saturn over four years of observation.
5
The Roche Limitis the radius at which a moon
will fragment into pieces due to the tidal
forceand form the fragments that make up a
ring.
6
Jovian Ring Systems are inside the Roche limit
7
Saturns Rings, with Earth shown for scale.
8
Saturns Rings, as seen in visible light and by
occultation of radio waves from the orbiter.
9
Saturns Rings, first half of full image.
10
Saturns Rings, second half of full image.
11
Saturns Rings, first quarter of full image.
12
Saturns Rings, second quarter of full image.
13
Saturns Rings, third quarter of full image.
14
Saturns Rings, fourth quarter of full image.
15
Saturns Rings have very fine structure, like
these ripples seen in just a small portion of the
rings.
16
Shepherd moons control the dynamics of parts of
the ring.
17
Pandora, a small moon, is the shepherd moon for
the thin and twisted F ring, the outermost ring
around Saturn.This shepherdmoon is outside
the ring.
18
Another shepherd moon in the Encke gap in the
rings around Saturn. This shepherd moon is
inside the gapand influences the edges of the
rings on either side of the gap.
19
The Encke gap in the rings,showing a twisted
thin ring in the gap.
20
The Encke gap in the rings.Notice the spiral
structure on the inner edge.
21
A shepherd moon causing waves in the edges of
the Keeler gap in the rings of Saturn.
22
These density waves in the rings of Saturn seem
to have a mathematical regularity.
23
(No Transcript)
24
Jupiters Faint Ring
25
Jupiters faint Rings were seen again in 2007 by
the New Horizons spacecraft on it way to Pluto.
26
Rings of Uranus top pictureshows detail of
the outermost ring
27
More Shepherd Moons
28
Neptunes Faint Rings
29
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.

30
Pluto can barely be resolved by telescopes from
Earth. This is the best available image of
Pluto.
31
Pluto and Charon are almost like a double planet.
32
The PlutoCharon Orbit is so unusual that it
probably means Charon is captured, and not
co-evolved with Pluto
33
Kuiper Belt ObjectsThe list is long. The
database has been automated and it is possible
to plot the positions of many of these objects.
34
This is a plot of actual positions of known
comets and asteroids (April 1, 2005). This
shows the inner solar system, out to Jupiter.
Notice most of these are in the asteroid
belt between Mars and Jupiter.
35
Expanding the first plot, we get a plot of
known comets and asteroids in the region
around the Earth. Fortunately, there arent
very many of these Near Earth Objects (NEOs).
36
This is the view from the side, i.e., in the
ecliptic plane, of the plot of the objects in
the inner solar system.
37
This is another plot of actual positions of
known comets and asteroids (April 1, 2005).
This shows the outer solar system, past the
orbit of Jupiter. Notice there is another
belt of objects out past Neptune.
38
This shows the outer solar system, past the
orbit of Jupiter. This is the view from the
side, i.e., in the ecliptic plane. Notice
that the comets are coming from all
directions, but the other objects are in the
ecliptic plane.
39
Kuiper Belt Objects Compared to Moon and Earth.
Notice that we think Triton was captured by
Neptune, and is really an object like Pluto and
the KBOs. The mission to Pluto and the KBOs is
called New Horizons. See http//pluto.jhuapl.edu
/ Also see this web page about KBOs
http//www.ifa.hawaii.edu/faculty/jewitt/kb.html