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Jovian Planets
Astronomy Picture of the Day
CPS Question
Which of the following provides the most
useful
information about the Earth's interior?
A) drilling
B) laser-ranging
C) x-rays
D) seismic waves
CPS Question
The _____ theory of lunar formation best
accounts for the observed similarities
and differences between the Earth and
the Moon.
A) fission
B) coformation
C) capture
D) impact
CPS Question
Which planet has a surface similar to
Earth's Moon
and has no appreciable atmosphere?
A) Mercury
B) Venus
C) Mars
D) Jupiter
Question
• Jupiter and Saturn were known to the
ancient astronomers. Uranus, barely
visible to the naked eye, was discovered
in 1781.
• Neptune is not visible to the naked eye.
How was it discovered?
Discovery of Neptune
Neptune predicted to exist because of irregularities
in Uranus' orbit.
Discovered in 1845 by Johann Galle.
Kepler’s and Newton’s laws in action!
Nice example of how the scientific method works!
Gravitational “Slingshots”
• Voyager 2 passed by ALL of the Jovian
planets during its flight. To do so, it
made use of “gravity assists”.
• How can a satellite “borrow” energy from
a planet that is orbiting the Sun?
Gravity Assists
• Satellite “borrows” energy from orbiting
planet
• Conservation of energy and Newton’s
third law
Gravity Assists (cont.)
• Precalculated before satellite is launched
• Also shows how gravity can eject “Planetesimals”
from early solar system
Question
Zones and belts are, respectively, high
and low
pressure systems on Jupiter.
What process would you expect to be
taking place
between such regions?
Why do the zones and belts stretch all the
Banded structure on other Jovian planets is present, but not as
distinct due to more uniform cloud coverage.
Saturn
Uranus:
bands obscured
by haze in
stratosphere
Neptune
Storms on Jovian Planets
Jupiter's Great Red Spot: A hurricane twice the size of Earth.
Has persisted for at least 300 years.
Neptune's Great Dark Spot: Discovered by Voyager 2
in 1989. About the size of the Earth.
Why do storms on Jovian planets last so long?
Other Rotational Effects
• Is the rotational bulge of the Jovian
planets more or less pronounced than
that of the terrestrials? Why?
Rapid rotation causes Jupiter and Saturn to bulge:
Gravity
Gravity
without rotation
with rotation
Jupiter and Saturn rotate once every ~10 hours.
Radius at equator several % larger due to gaseousliquid composition of the Jovians.
The Jovians are not solid bodies. What other effect
does this have on their rotations?
Differential Rotation
Rotation period is shorter closer to the equator:
Near poles
At equator
Jupiter
9h 56m
9h 50m
Saturn
10h 40m
10h 14m
Uranus
16h 30m
14h 12m
How do we know?
Differential Rotation
Rotation period is shorter closer to the equator:
Near poles
At equator
Jupiter
9h 56m
9h 50m
Saturn
10h 40m
10h 14m
Uranus
16h 30m
14h 12m
How do we know? Tracking storms at various
latitudes, or using Spectroscopy and Doppler shift.
Differential Rotation
• Density of Jovians increases with depth
• Rapid “core” rotation
• Frictional dragging of outer atmosphere.
Most efficient at equator, least at poles.
Question
• Uranus' axis of rotation lies almost in the
plane of its orbit! What effect does this
have on the Uranian seasons?
Uranus' rotation axis is tilted by 98o
Why? Unknown. Perhaps an early, grazing collision with
another large body.
● Most extreme seasons of any planet!
● Polar regions - alternately light and dark for 42 years
●