survey of astronomy astro1010-lee.com [email protected] chapter 11 jupiter – lord of the planets
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Chapter 11JUPITER – Lord of the Planets
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Chapter 11To discuss the Jovian Planets we must first talk
about The Voyager program. The mission of Voyager 1 & 2 is to visit the Outer Solar System and beyond.
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Chapter 11This is the Voyager 2 velocity profile showing the velocity flips
at each planet. Our booster was barely able to reach Jupiter with-out gravity assist. With gravity assistwe have left the Solar System
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Chapter 11
Jupiter can be imaged well from Earth, even with a small telescope
Here: Jupiter with its Galilean moons
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Chapter 11
Earth Pioneer 1973
Voyager 1979
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Chapter 11•Mass: More than twice as much as all other
planets put together.
• Radius: 11.2 times Earth’s radius
• Density: Only 1.3 x the density of water – cannot be rocky or metallic as terrestrial planets are
• Rotation Rate: problematic, as Jupiter has no solid surface; different parts of atmosphere rotate at different rates. The solution came from magnetic field, whose rotation period is 9 hr, 55 min
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Chapter 11
Early images of Jupiter showed the Great Red Spot and Stripes. As ourinstruments improved many more details emerged. The spot became a giant storm and stripes became bands of rising and falling gases.
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Chapter 11
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Great Red Spot has existed for at least 300 years, possibly much longer.
It seems to be and inverted storm dipping to the planet rather that rising above it.
The colors have changed over the years from brick red to light brown.
The size has changed from 3x the size of the Earth to just over 2x.
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Chapter 11
The Atmosphere has bright zones and dark belts. Zones are rising warmer gasses from the interior, and are higher than belts. The Belts are cooler falling gases returning to be re-warmed. The many storms seen in the belts are due to turbulence caused by differential rotation in the atmosphere
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Chapter 11
The composition of the Atmosphere is mostly molecular hydrogen and helium with small amounts of methane, ammonia, and water vapor. The impurities seem to account for the colors, probably due to complex chemical interactions that we are still studying
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Chapter 11
No solid surface; take top of troposphere to be 0 km
The lowest level of the atmosphere is the stripes. Telescopes can not see through it.
Measurements by Galileo probe show high wind speeds even at great depth – probably due to heating from inside the planet, not from Sun
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Chapter 11Great Red Spot has existed for at least 400 years, possibly
much longer
Color and energy source still not fully understood
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Chapter 11
Lightning-like flashes have been seen; also shorter-lived rotating storms
One example: Brown Oval, really a large gap in clouds
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Chapter 11We find that Jupiter radiates more energy than
it receives from the Sun:
Core is still cooling off from heating during gravitational compression.
Could Jupiter have been a star?
No; it is far too cool and too small for that. It would need to be about 80 times more massive to be even a very faint star
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Chapter 11No direct
information is available about Jupiter’s interior, but its main components, hydrogen and helium, are quite well understood. The central portion is a rocky core.
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Chapter 11Jupiter is surrounded by belts of charged particles, much like
the Van Allen belts but vastly larger Magnetosphere is 30 million km across
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Chapter 11
Intrinsic field strength is 20,000 times that of Earth
Magnetosphere can extend beyond the orbit of Saturn
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Chapter 11More than 60 moons have now been found
orbiting Jupiter, but most are very small.
The four largest are the Galilean moons, so called because they were first observed by Galileo:
• Io, Europa, Ganymede, Callisto
Galilean moons have similarities to terrestrial planets; orbits have low eccentricity, largest is somewhat larger than Mercury, and density decreases as distance from Jupiter increases
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Chapter 11
The Small moons move in mostly eccentric orbits far from Jupiter. Here, the orbits of the Galilean moons can be seen in the center near the planet.
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Chapter 11
These are the Galilean moons. Each is unique. Each is interesting.
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Chapter 11
The Galileo Probe has given us a very good feel for their interiors
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Chapter 11Io is the most dense of Jupiter’s moons, and the most
geologically active object in the solar system. It has many active volcanoes, some quite large. It can change surface features in a few weeks There are no impact craters; they fill in too fast – Io has the youngest surface of any solar system object. The many colors come from sulfur at different temperatures
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Chapter 11
The vulcanism on Io is due to tidal forces. Io is very close to Jupiter in a rather eccentric orbit, and also experiences gravitational forces from Europa and Ganymede. The tidal forces are huge and provide the energy for the Volcanoes. This image of Io is the discovery image for the volcanos
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Chapter 11Volcanic eruptions also eject charged
particles; these interact with Jupiter’s magnetosphere and form a plasma torus
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Chapter 11
The moon Europa has no impact craters, The surface is water ice, likely with liquid water below
Tidal forces stress and crack the ice allowing liquid water to flow out keeping surface glass smooth
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Chapter 11Ganymede is the largest moon in the solar system –
larger than the planet Mercury
Impact history similar to Earth’s Moon, but water ice and dirt instead of lunar rock
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Chapter 11Surface areas of Ganymede once thought
to be cratered and flat turn out to have structures. These may be due to a form of plate tectonics
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Chapter 11Calisto is similar to Ganymede except
there is no evidence of plate activity.
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Chapter 11One of the big surprises of the Voyager
program was the discovery of a ring around Jupiter. This is the discovery image.
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Chapter 11These four moonlets are associated with
Jupiter’s ring. The two tiniest, Metis and Adastria are embedded in the ring and seem to be shattering to feed the ring. The other two, Amalthea and Thebe, are “Shepherd” moons.
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Chapter 11This image made by the Galileo spacecraft
shows more details. Especially evident are the sharp outer edge and the diffuse inner edge of the ring and the detail within the rings are explained by the presence of the moonlets.
