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Jupiter is the fifth planet from the Sun and the largest planet in the Solar System.[11] It is a gas giant with mass one-thousandth of that of the Sun but is two and a half times the mass of all the other planets in the Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian or outer planets. The planet was known by astronomers of ancient times,[12] and was associated with the mythology and religious beliefs of many cultures.
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Astro 102/104 1
Lecture #26: Jupiter• Jupiter:
– General properties.– Atmosphere.– Interior.– Origin and evolution.
• Readings: 7.1 (Jupiter), 11.1
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The Main Point
Jupiter is the largest planet in the solar system by far, and is made almost entirely
of the same “stuff” as the Sun.
Astro 102/104 3
The Jovian Planets
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Basic Properties of Jupiter• Average Distance from Sun: 778,000,000 km (a=5.20 AU).• Orbital period: 11.86 years; eccentricity: 0.048.• Period of Spin around axis: ~10 hours (varies with latitude).• Tilt of Jovian spin axis: 3.1° (no real seasons).• Mass: 1.9x1027 kg = 317 ME ; Radius: 71,400 km = 11 RE. • Density = 1.3 g/cm3 (mostly gaseous, small "rocky" core?)• No "surface" like the terrestrial planets: only clouds visible.• Gravity = 24.8 m/sec2 (2.5 times Earth's).• Cloud-top temperature: 125 K (-148°C).• Atmosphere: Mostly H, He (plus CH4, NH3, H2O, NH4HS, ...).• Moons: 63 presently known (48 have been named).• Rings: Jupiter has an elegant set of thin dark rings.
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Observations• Jupiter is a prominent object in the night
sky for many months out of each year.• Through even a small telescope, Jupiter's clouds
appear yellow, red, & brown.• And features can be seen:
– Belts of red clouds.– Zones of white clouds.– Oval-shaped storms.
Astro 102/104 6
Space Missions
• 8 robotic spacecraft have flown past Jupiter.Mission Dates Goals and Results Pioneer 10 1973 First Jupiter flyby; studied magnetic field, clouds.Pioneer 11 1974 Flyby; studied magnetic field, atmosphere.Voyager 1 1979 Flyby; high resolution imaging and other studies.Voyager 2 1979 Flyby; high resolution imaging and other studies.Ulysses 1992 Flyby (gravity assist); solar wind & magnetic field.Galileo 1995- Orbiter; imaging, spectroscopy, magnetic fields,
and atmospheric entry probe.Cassini 1999 Flyby (gravity assist); imaging, spectroscopy.New Horizons 2007 Flyby (gravity assist); imaging, spectroscopy.
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Grand Tour of the Voyager Spacecraft
Astro 102/104 8
Jupiter's Dynamic Atmosphere• The zones, belts, and storms change with time.
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Astro 102/104 9
Belts & ZonesKnowledge of the composition and temperature allows astronomers to create a model to explain the distribution and colors of the belts and zones.
Zones: rising air forms white ammonia clouds.Belts: falling air forms no white clouds and reveals red clouds below.
Astro 102/104 10
Atmospheric Circulation
The most famous storm, the Great Red Spot, has been around at least since 1610.
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Atmospheric Composition• Determined by spectroscopy from
telescopes and spacecraft.• Directly by the Galileo probe.
Name Symbol % Volume Hydrogen H2 86Helium He 13.6 Methane CH4 1.8 x 10-3
Ammonia NH3 2.6 x 10-4
Ethane C2H6 6 x 10-6
Deuterated Hydrogen HD 5 x 10-5
Water vapor H2O <=6 x 10-4
Deuterated Methane CH3D 3 x 10-5
Phosphine PH3 1 x 10-6
Carbon monoxide CO 1 x 10-7
Germanium Tetrahydride GeH3 ? 1 x 10-7
The composition of Jupiter is very close to the composition of the Sun.
Galileo Probe Mission
Release Date: 7/13/95 Entry into Jupiter: 12/7/95Entry Speed: 106,000 mphProbe Data Return:
59 min3.5 megabits
Penetration depth 200 km (124 mi)
Astro 102/104 12Atmospheric Structure: Direct measurements from the Galileo entry probe in 1995.
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Probe Results:• Composition close to (but not
exactly) solar.• Cloud structure close to that
predicted.• Circulation is “deep” rather than
“shallow”.• H2O is distributed very non-
uniformly.• Complex hydrocarbon molecules
more scarce than predicted.Astro 102/104 14
• How can we know?– Orbits of inner moons.– Trajectories of spacecraft.– Shape of the planet ("oblateness").– Interior rotation rate (from magnetic field).
• Models:– Solar composition.– Phase diagram of H, He (gas, liquid, "metal").
Jupiter's Interior ??
Astro 102/104 15
Jupiter's Interior
Interior structure is inferred from models and extrapolation of data from the upper cloud layers...
Astro 102/104 16
Internal vs. External Heat Sources• Energy Balance:
– Energy in = Energy out.– Solar heat absorbed = Outgoing planetary heat.
• But for Jupiter: Outgoing = 1.8 × Incoming.• Jupiter has a strong internal heat source:
– Heat stored from planetary contraction?• This has a strong influence on atmospheric
circulation and “climate”.
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Astro 102/104 17
Giant Planet or Failed Star?
• Calculations suggest that Jupiter is about 80 times less massive than needed to initiate hydrogen fusion reactions in its core and become a star.
• Some people have called Jupiter a “failed star” for this reason, but it might better be thought of as a very successful planet.
Astro 102/104 18
Jupiter's Magnetic Field• One of the largest planetary structures in the
solar system (apparent size > the full Moon).• Jupiter's magnetic field is
about 20,000 times stronger than Earth's.
• The solar wind is deflected in a huge zone around the planet.
• Evidence for the magnetic field can be seen in telescope and spacecraft images of aurorae.
Astro 102/104 19
Jupiter's Magnetic Field• Field is tilted slightly
relative to the spin axis.• Intense toroidal zone of
charged particles coming from Io's volcanoes.
• Extended "sheet" of plasma along magnetic equator.
• Entire structure oscillates at Jupiter's spin rate.
Jupiter L Burst Jupiter S BurstAstro 102/104 20
Satellites & Rings• Galileo discovered the 4 large moons of
Jupiter (the Galilean satellites) in 1610.• 12 other smaller rocky/icy
bodies found from 1872-1979.• 51 more very small, outer moons
discovered in 1999-2005.• Many more details in Lectures 30 & 31.
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Summary
• Jupiter is a gas giant planet, composed mostly of H and He in the same relative abundances as the Sun.
• Jupiter has vigorous atmospheric circulation that manifests itself as long-lived belts, zones, & storms.
• Jupiter's interior consists of liquid and metallichydrogen, at enormous temperatures and pressures.
• Jupiter has a very large magnetic field that interacts strongly with the satellites and the solar wind.
• Jupiter has 63 known satellites…Astro 102/104 22
Next Lecture...
• Saturn:– General properties.– Atmosphere.– Interior.– Origin and evolution.
•• Readings: 7.1 (Saturn), 11.1 Readings: 7.1 (Saturn), 11.1