AST 111 Lecture Notes - Lecture 17: Roche Limit, Rings Of Saturn, Aurora

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12 Nov 2015
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AST 111: Lect 17-Jupiter and Saturn (cont.)
-Metallic H inside Jupiter and Saturn allows the planets to have large magnetic fields
The field originates in the reservoir of (liquid) hydrogen that comprises most of
the hydrogen
oThe formal name of the super condensed hydrogen is “liquid metal
hydrogen”
oIt is electrically conducting
This means that the large planets have a very strong dynamo
Jupiter’s magnetic field is much stronger because it has much more liquid metal
hydrogen than Saturn
oJupiter’s magnetic field extends all they way to the orbit of Saturn
oIt is slightly tipped (11)
Similar to the misalignment on Earth!
oThe magnetic field of Jupiter rotates in about 9 hours and 55 minutes
THIS IS HOW THE ROTATION OF THE JOVIAN PLANETS IS
DEFINED
The difference between the rotation of the magnetic fields and the
rotation of the cloud tops is how we determine wind speed on these
planets
Saturn’s magnetosphere is much smaller than Jupiter
Jupiter and Saturn both produce spectacular aurorae!
Nasa’s JUNO MISSION will study the interior structure and magnetic field of
Jupiter
oIts goals:
Investigate the core
Map the magnetic field
Determine the amount of water and ammonia
Observe the aurora
-Earth based observations reveal 3 broad rings around Saturn
Galileo saw puzzling “bumps” that disappeared, then reappeared
Huygens suggested that Saturn was surrounded by flat rings
oHe was pretty much right!
Cassini noticed the division between the A and B rings
oCalled the Cassini Division
The rings are NOT SOLID!
oMade of many fine particles called ringlets
oObserved by sending radio transmissions THROUGH the rings
It was determined that a typical particle is about 10 cm in size
The rings are very reflective, so they are probably ice particles or
ice covered rock
oThe rings closer to the planet orbit the planet faster than the rings on the
outside
The rings have “spokes” (discovered by Voyager)
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