Jupiter

Jan. 23, 2005 jeb

OUTLINE
• General Properties of Jupiter
• History of Observations from Earth
• Space Probes to Jupiter
• Jupiter's Atmosphere
• Jupiter's Internal Structure
• Jupiter's Magnetosphere
• Moons of Jupiter
• Galilean Moons
• Jupiter's Ring
• Jupiter as a "failed star"
• Jupiter's Basic Properties
• Jupiter's Golden Globe Awards
• Other sources on Jupiter

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Jupiter is the third brightest object in the night sky (after the Moon and Venus)

Jupiter is named for the most powerful god of the Roman pantheon

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General Properties of Jupiter

• Jupiter is the 5th Planet from the Sun
  
• semi-major axis ("radius" of orbit) = 5.20 AU
  • 4.95 AU at perihelion
  • 5.46 AU at aphelion

• orbital period = 11.86 years
  • This follows from KEPLER'S LAW and the size of the semi-major axis:
    • square of the orbital period ~ (semi-major axis)³
    • ...................................... = (5.2)³
    • ...................................... = 140
    • ...............orbital period = 11.86 years

• Radius = 71,492 km = 11.21 R_earth (at the equator)
• Mass = 1.9 x 10²⁷ kg = 317.8 M_earth
  • More than twice as massive as all the rest of the planets combined
• => Density = 1330 kg/m³
  • (just a bit denser than water)

• Rotational Period = 0.41 days (nearly 10 hours)
• Axial tilt (Inclination) of 3.08°
• Differential rotation
  • period of rotation at equator = 9^h50^m
  • period of rotation at higher latitudes = 9^h55^m
• Equatorial bulge

• Prominent visual features
  • Dark bands
  • Great Red Spot
  • four prominent moons
    • Discovered by Galileo in 1609

History of Observations from Earth

• Being the third brightest object in the night sky, Jupiter was known to early humans
• 1609 - Galileo turns his telescope on Jupiter and discovers the moons

• It takes over half an hour for light (or radio signals from a spacecraft) to get from Jupiter to the Earth

Space Probes to Jupiter

• Pioneer 10 - (launched by USA, March 3, 1972)
  • Pioneer 10 flew by Jupiter on December 1, 1973, passing about 130,000 kilometers from Jupiter's cloud tops.
  • Returned over 500 images of Jupiter and its moons and much scientific data
    • magnetic field, trapped charged particles, and solar wind interactions
  • Pioneer 10 has now left the solar system
    • Carrying a gold, anodized plaque intended to communicate with extraterrestrials

• Pioneer 11 - (launched by USA, April 6, 1973)
  • Pioneer 11 flew by Jupiter on December 1, 1974, passing about 43,000 kilometers from Jupiter's cloud tops.
  • Returned even better pictures than Pioneer 10
  • measured Jupiter's intense charged-particle and magnet field environment
  • Gravity assist from Jupiter directed Pioneer 11 toward Saturn
  • Pioneer 11 has now left the solar system
    • Also carrying a plaque, as Pioneer 10

• Voyager 1 - (launched by USA, September 5, 1977)
  Voyager 1 flew by Jupiter on March 5, 1979
  • Continued on to Saturn

• Voyager 2 - (launched by USA, August 20, 1977)
  Voyager 2 flew by Jupiter on July 9, 1979
  • Continued on to Saturn, Uranus, and Neptune.

• Galileo - (launched by USA and Europe, October 18, 1989)
  Galileo was designed to study Jupiter's atmosphere, satellites and surrounding magnetosphere for 2 years.
  • Galileo used gravity assist techniques to pick up speed from Venus and Earth
    • flew past Venus on February 10, 1990
    • flew past the Earth & Moon on December 8, 1990 and
    • flew past the Earth & Moon again on December 8, 1992
    During the journey, Galileo made encounters with asteroids
    • Gaspra on October 29, 1991
    • Ida and moon Dactyl on August 28, 1993.
  • During voyage, had direct view of the Comet Shoemaker-Levy impacts on Jupiter (July, 1994)
  • Arrived at Jupiter, December, 1995
  • Significantly advanced our knowledge of the Galilean moons

Jupiter's Atmosphere

Bands and Spots:
• very complex chemistry
• persistent storms

Elements:
• 86.1% hydrogen (by number)
  
• 12.8% helium (by number)
  
• little of the early atmosphere escaped due to the strong gravity (large escape velocity)
  

Clouds: Bands and Spots caused by different chemistry vs. altitude
• Zones (light; warm, rising regions)
• Belts (dark; cool, falling regions)
  Zonal Flow
  
  Giant Red Spot
  • Large hurricane in the south
    • about 2 times the size of Earth
    • at least 300 years old
  • revolves with inner region of Jupiter
  • rotates counterclockwise
    • high pressure region -> gas flows outward
      • opposite of hurricane on Earth -> low pressure region
  
  Other storm related features
  • gigantic lightning flashes
  • Auroral activity
  • White ovals
    • southern hemisphere
    • live for decades
  • Brown ovals
    • northern hemisphere
    • "hole" allowing view deep into atmosphere
    • persist for many years or decades

Jupiter's Internal Structure

Emits twice as much energy as it receives from the Sun
• ---> internal heat built up during Jupiter's formation is slowly leaking out
  • gravitational energy
Atmosphere gets denser and denser towards its interior
• gaseous hydrogen
• liquid hydrogen
• liquid metallic hydrogen (generates large magnetic field)
• rocky core (15 x's Earth's mass)

Jupiter's Magnetosphere

Intrinsic strength of magnetic field about 20,000 times Earth
• magnetic field at cloud top 14 times Earth's surface field

Very large magnetosphere
----> larger than size of the sun

Large sea of trapped, charged particles
----> like Van Allen Belts

Vastly larger and more energetic Aurorae than on Earth

Plasma torus (moon Io)

Moons of Jupiter

61 known moons
16 major moons of greater than 10 km diamter

Table of major moons

Four sets of major moons

four moons in each of the 4 sets
All are tidally locked

1.) Inner moons (inside Galilean) = 4 small moons

2.) Galilean moons ( 4 moons)
• largest, similar in size to Earth's Moon
• named for mythical attendants of Roman god, Jupiter.
  ---->Io, Europa, Ganymede, Callisto

3., 4.) Outer moons ----> 2 sets of 4 major moons

• Each set appears to have been a single body,
  captured by Jupiter, then broken into sections.


Orbital motion of major moons
• inner 3 sets are prograde
• outer set is retrograde

Galilean Moons

all rotate synchronously (tidal lock)
photo of Io and Europa
Internal structure of four Galilean moons
Galileo spacecraft took a tour of discovery around the Galilean moons

• orbits Jupiter at 5.9 times Jupiter's radius
  • ---> (recall Earth's Moon orbits at about 60 Earth radii)
• Most geologically active object in Solar System
  • Voyager I photographed 8 erupting volcanoes
  • Voyager II (4 months later) 6 still active
  • VERY strong eruptions

• Smooth surface- molten matter filling
  
• sulfur - on surface, thin atmosphere
  
• plasma torus produced
• volcanoes caused by Jupiter's tidal forces + Europa's influence
  • ---> non-circular orbit

• at 9.4 radii
• few craters
  • young surface
• surface network of lines :
  • cracks in ice cover?
  • tectonic activity?
  • -of ice
  • icebergs?
  • Ocean?
  • Life? !

• at 15 radii
• largest moon in Solar System (larger than Moon, Mercury or Pluto)
• less dense than Io or Europa
• ---> largely ice
• large cratering and maria (but of water)
• grooved terrain

• at 26 radii
• cratering and concentric rings

Jupiter's Ring:

Faint ring discovered by Voyager I
• Main ring lies above cloud layer and inside orbit of innermost moon
• Galileo spacecraft has explored the ring, and its interaction with the inner moons in detail
• Conclusion: the ring system (main ring + gossamer rings) has been formed by the dust kicked up when interplanetary meteoroids smash into the inner moons

Jupiter as a "failed star"

Other Sources on Jupiter

StarDate Guide to Jupiter
Welcome to the Planets - Jupiter
Views of the Solar System - Jupiter
The Nine Planets - Jupiter