1. April 10, 2006 Astronomy 2010 1 Giant Planets

2. April 10, 2006Astronomy 20102 Jupiter Saturn UranusNeptune Jovian Worlds

3. April 10, 2006Astronomy 20103Exploration First spacecrafts: pioneer 10 (1972) & 11 (1973). First spacecrafts: pioneer 10 (1972) & 11 (1973). Can we navigate through the asteroid belt? Can we navigate through the asteroid belt? What are the radiation hazards near the planets? What are the radiation hazards near the planets? Pioneer 10 flew by Jupiter 1973 and flew out the solar system. Pioneer 10 flew by Jupiter 1973 and flew out the solar system. Pioneer 11 flew by Jupiter 1974 and was deflected towards Saturn which it reached in 1979. Pioneer 11 flew by Jupiter 1974 and was deflected towards Saturn which it reached in 1979.

4. April 10, 2006Astronomy 20104 Exploration Voyager 2 Voyager 1 & 2 (launched 1977) Voyager 1 & 2 (launched 1977) Highly productive Missions Highly productive Missions Carried 11 scientific instruments including cameras and spectrometers, devices to measure the magnetospheres Carried 11 scientific instruments including cameras and spectrometers, devices to measure the magnetospheres Voyager 1 Voyager 1 Reached Jupiter 1979 and Saturn 1980 Reached Jupiter 1979 and Saturn 1980 Used gravity assist towards Saturn Used gravity assist towards Saturn Voyager 2 Voyager 2 Reached Jupiter four month later than Voyager 1 Reached Jupiter four month later than Voyager 1 Reached Saturn 1981, Uranus 1986, Neptune 1989 Reached Saturn 1981, Uranus 1986, Neptune 1989 Multiple Flybys possible thanks to approximate alignment of the planets - occurs once in 175 years Multiple Flybys possible thanks to approximate alignment of the planets - occurs once in 175 years

5. Voyager 2

6. April 10, 2006Astronomy 20106Exploration Galileo space probe Galileo space probe Launched 1989 Launched 1989 Reached Jupiter December 1995 Reached Jupiter December 1995 Deployed a small entry probe for a direct study of Jupiter’s atmosphere Deployed a small entry probe for a direct study of Jupiter’s atmosphere Sept. 2003, probe sent into Jupiter’s atmosphere to end its mission. Sept. 2003, probe sent into Jupiter’s atmosphere to end its mission. Cassini Cassini Launched 1997 Launched 1997 Reached Saturn in 2004, now in orbit. Reached Saturn in 2004, now in orbit. Will deploy entry probe for Titan in Jan 2005 Will deploy entry probe for Titan in Jan 2005

7. Galileo Space Probe

8. April 10, 2006Astronomy 20108 Mass 339 kg Mass 339 kg Plunged at shallow angle into Jupiter at speed of 50 km/s. Plunged at shallow angle into Jupiter at speed of 50 km/s. Slow down by friction against the Jovian atmosphere, temperature of shield to 15000 o C Slow down by friction against the Jovian atmosphere, temperature of shield to 15000 o C Speed dropped to 2500 km/h Speed dropped to 2500 km/h Deployed parachute for actual entry in the atmosphere Deployed parachute for actual entry in the atmosphere Transmission of data to orbiter – retransmission to Earth Transmission of data to orbiter – retransmission to Earth 57 minute descent/recording 57 minute descent/recording 200 km downward/500 km sideward 200 km downward/500 km sideward Galileo – Jupiter Entry Probe

9. April 10, 2006Astronomy 20109 Some Scientific results of the Galileo mission The discovery of a satellite (Dactyl) of an asteroid (Ida). The discovery of a satellite (Dactyl) of an asteroid (Ida). Confirmation of the existence of a huge ancient impact basin in the southern part of the Moon's far side (inferred from Apollo data but never before mapped). Confirmation of the existence of a huge ancient impact basin in the southern part of the Moon's far side (inferred from Apollo data but never before mapped). Evidence of more extensive lunar volcanism than previously thought. Evidence of more extensive lunar volcanism than previously thought. Discovery of an intense interplanetary dust storm (the most intense ever observed). Discovery of an intense interplanetary dust storm (the most intense ever observed). Discovery of an intense new radiation belt approximately 50,000 km (31,000 miles) above Jupiter's cloud tops. Discovery of an intense new radiation belt approximately 50,000 km (31,000 miles) above Jupiter's cloud tops. Jovian wind speeds in excess of 600 kilometers per hour (> 400 mph) were detected. Jovian wind speeds in excess of 600 kilometers per hour (> 400 mph) were detected. Far less water was detected in Jupiter's atmosphere than estimated from earlier Voyager observations and from models of the Comet Shoemaker-Levy 9 impact. Far less water was detected in Jupiter's atmosphere than estimated from earlier Voyager observations and from models of the Comet Shoemaker-Levy 9 impact. Far less lightning activity (about 10% of that found in an equal area on Earth) than anticipated. The individual lightning events, however, are about ten times stronger on Jupiter than the Earth. Far less lightning activity (about 10% of that found in an equal area on Earth) than anticipated. The individual lightning events, however, are about ten times stronger on Jupiter than the Earth. Helium abundance in Jupiter is very nearly the same as its abundance in the Sun (24% compared to 25%). Helium abundance in Jupiter is very nearly the same as its abundance in the Sun (24% compared to 25%). Extensive resurfacing on Io due to continuing volcanic activity since the 1979 Voyagers fly-bys. Extensive resurfacing on Io due to continuing volcanic activity since the 1979 Voyagers fly-bys. Preliminary data support the evidence of magnetic fields for both Io and Ganymede. Preliminary data support the evidence of magnetic fields for both Io and Ganymede. Evidence for liquid water ocean under Europa's ice. Evidence for liquid water ocean under Europa's ice.

10. Jovian Planets - Basics Large distance from the sun. Large distance from the sun. Long period. Long period. Jupiter/Saturn similar in composition + internal structure. Jupiter/Saturn similar in composition + internal structure. Uranus/Neptune smaller, differ in composition and structure. Uranus/Neptune smaller, differ in composition and structure. Basics Properties of the Jovian Planets PlanetDistance (AU) Period (years) Diameter (km) Mass (Earth=1) Density (g/cm3) Rotation (hours) Jupiter5.211.91428003181.39.9 Saturn9.529.5120540950.710.7 Uranus19.284.151200141.217.2 Neptune30.1164.849500171.616.1

11. April 10, 2006Astronomy 201011Appearance Only the upper atmosphere of the giant planets is visible to us Only the upper atmosphere of the giant planets is visible to us Composed primarily of hydrogen and helium gas Composed primarily of hydrogen and helium gas Jupiter/Saturn Jupiter/Saturn Uppermost clouds made of ammonia crystals (NH 3 ) Uppermost clouds made of ammonia crystals (NH 3 ) Neptune Neptune Methane (CH 4 ) Methane (CH 4 ) Uranus Uranus no clouds, featureless haze no clouds, featureless haze

12. April 10, 2006Astronomy 201012Rotation How does one determine the rotation rate of the giants? How does one determine the rotation rate of the giants? On Jupiter: On Jupiter: 1 st option: Use dynamic surface features (storms). 1 st option: Use dynamic surface features (storms). However the cloud rotation may have nothing to do with the rotation of the mantle and core… However the cloud rotation may have nothing to do with the rotation of the mantle and core… 2 nd option: look at periodic variations of radar waves associated with the magnetic field produced deep inside the planet. 2 nd option: look at periodic variations of radar waves associated with the magnetic field produced deep inside the planet. Rotation 9h 56 min. Rotation 9h 56 min. Same technique used to measure the rotation of other giant planets: Same technique used to measure the rotation of other giant planets: Saturn : 10h40 m. Saturn : 10h40 m. Uranus/Neptune : ~ 17 hours. Uranus/Neptune : ~ 17 hours.

13. Jupiter tilted by 3 o No seasons to speak of. Saturn Tilted by 27 o Long seasons Neptune Tilted by 27 o Long seasons. Seasons on the Giants Uranus Tilted by 98 o Practically orbiting on its side Rings + satellites follow same pattern 21 year seasons!!! Why this odd tilt? Giant impact!

15. April 10, 2006Astronomy 201015 Giant Planets – Giant Pressure Giant planets composed mainly of H, He, but… Giant planets composed mainly of H, He, but… Because of its enormous size, hydrogen and helium in the center of Jupiter is compressed enormously –. Because of its enormous size, hydrogen and helium in the center of Jupiter is compressed enormously –. Estimated pressure: 100 million bars. Estimated pressure: 100 million bars. Central density of 31 g/cm 3. Central density of 31 g/cm 3. Earth by contrast has 4 million bars and 17 g/cm 3 in its center. Earth by contrast has 4 million bars and 17 g/cm 3 in its center. Giant Planet implies Giant Pressure!! Giant Planet implies Giant Pressure!!

16. April 10, 2006Astronomy 201016 Consequences of the Pressure Few 1000 km below the surface, hydrogen is in a liquid state Few 1000 km below the surface, hydrogen is in a liquid state Still deeper, the liquid is further compressed and begins to act like a metal. Still deeper, the liquid is further compressed and begins to act like a metal. On Jupiter part of the interior is metallic hydrogen! On Jupiter part of the interior is metallic hydrogen! Saturn is less massive – most of its interior is liquid – but not metallic. Saturn is less massive – most of its interior is liquid – but not metallic. Neptune/Uranus are probably too small to liquefy hydrogen Neptune/Uranus are probably too small to liquefy hydrogen

17. April 10, 2006Astronomy 201017 More about Composition The planets also have a core composed of heavier materials The planets also have a core composed of heavier materials Possibly the original rock/ice bodies that formed before gas were abundantly captured by the planets. Possibly the original rock/ice bodies that formed before gas were abundantly captured by the planets.

18. April 10, 2006Astronomy 201018 Internal Heat Source (1) Because of their large sizes, all giant planets were strongly heated during their formation - Jupiter was the hottest Because of their large sizes, all giant planets were strongly heated during their formation - Jupiter was the hottest Some of the primordial heat still remains Some of the primordial heat still remains Giant planets may also generate energy internally by slowly contracting Giant planets may also generate energy internally by slowly contracting Even a small amount of shrinkage can generate significant heat Even a small amount of shrinkage can generate significant heat Raises the temperature of the core and atmosphere above the temperature due to the Sun energy supply. Raises the temperature of the core and atmosphere above the temperature due to the Sun energy supply. Jupiter has the largest internal source of energy Jupiter has the largest internal source of energy 4x10 17 Watts 4x10 17 Watts A cross between a planet (like earth) and a star A cross between a planet (like earth) and a star Internal heat is primordial heat Internal heat is primordial heat

19. April 10, 2006Astronomy 201019 Magnetic Fields All four giant planets have strong magnetic fields and associated magnetospheres All four giant planets have strong magnetic fields and associated magnetospheres The magnetospheres are large – extend for millions of km in space The magnetospheres are large – extend for millions of km in space Jupiter’s field was discovered in the late 1950’s Jupiter’s field was discovered in the late 1950’s Radio waves detected from Jupiter Radio waves detected from Jupiter Electrons circulating in the magnetosphere produce the radio waves by a process called synchrotron emission. Electrons circulating in the magnetosphere produce the radio waves by a process called synchrotron emission. Magnetic fields of Saturn, Uranus, and Neptune discovered by flyby spacecraft. Magnetic fields of Saturn, Uranus, and Neptune discovered by flyby spacecraft.

20. April 10, 2006Astronomy 201020Magnetospheres Jupiter’s magnetic field not aligned with its axis of rotation. – tipped by 10 o Jupiter’s magnetic field not aligned with its axis of rotation. – tipped by 10 o Uranus/Neptune have tilts of 60 o and 55 o. Uranus/Neptune have tilts of 60 o and 55 o. Saturn’s field is perfectly aligned with its axis of rotation. Saturn’s field is perfectly aligned with its axis of rotation.

21. April 10, 2006Astronomy 201021 Atmospheres The part of the planets accessible to direction observation. The part of the planets accessible to direction observation. Dramatic examples of weather patterns. Dramatic examples of weather patterns. Storms on these planets can be larger than Earth! Storms on these planets can be larger than Earth!

22. April 10, 2006Astronomy 201022 Atmospheric Composition Methane (CH 4 ) and ammonia (NH 3 ) were first believed to be the primary constituents of the atmospheres. Methane (CH 4 ) and ammonia (NH 3 ) were first believed to be the primary constituents of the atmospheres. We know today that hydrogen and helium are actually the dominant gases. We know today that hydrogen and helium are actually the dominant gases. First based on far-infrared measurements by Voyager First based on far-infrared measurements by Voyager Less helium in Saturn’s atmosphere Less helium in Saturn’s atmosphere Precipitaion of Helium? Energy Source of Saturn? Precipitaion of Helium? Energy Source of Saturn? Best measurements of composition by Galileo spacecraft (1995) upon atmosphere entry. Best measurements of composition by Galileo spacecraft (1995) upon atmosphere entry.

23. April 10, 2006Astronomy 201023 Clouds and Atmospheric Structure Jupiter’s clouds are spectacular in color and size. Jupiter’s clouds are spectacular in color and size. Color: orange, red, brown Color: orange, red, brown Fast motion Fast motion Saturn is more “subdued”: clouds have nearly uniform butterscotch hue. Saturn is more “subdued”: clouds have nearly uniform butterscotch hue.

24. April 10, 2006Astronomy 201024 Winds and Weather Many regions of high/low pressure Many regions of high/low pressure Air flow between these regions Air flow between these regions Sets up wind patterns distorted by the fast rotation of the planet. Sets up wind patterns distorted by the fast rotation of the planet. Wind speeds measured by tracking cloud patterns. Wind speeds measured by tracking cloud patterns. Differences with Earth Differences with Earth Giant planets spin much faster than Earth Giant planets spin much faster than Earth Rapid rotation smears out air circulation into horizontal (east-west) patterns parallel to the equator. Rapid rotation smears out air circulation into horizontal (east-west) patterns parallel to the equator. No solid surface No solid surface No friction or loss of energy – why tropical storms on Earth eventually die out… No friction or loss of energy – why tropical storms on Earth eventually die out… Internal Heat contributes as much energy to the atmosphere as sunlight (except for Uranus). Internal Heat contributes as much energy to the atmosphere as sunlight (except for Uranus).

25. April 10, 2006Astronomy 201025 What causes the winds? Coriolis Effect! Coriolis Effect!

26. April 10, 2006Astronomy 201026

29. April 10, 2006Astronomy 201029 Jupiter/Saturn Winds

30. April 10, 2006Astronomy 201030 Uranus/Neptune Winds Rather similar to the winds on Jupiter/Satrun Rather similar to the winds on Jupiter/Satrun True on Uranus in spite of the 98 O tilt. True on Uranus in spite of the 98 O tilt.

31. April 10, 2006Astronomy 201031Storms Always present on the giant planets Always present on the giant planets Superimposed on the regular circulation patterns Superimposed on the regular circulation patterns Large oval shape high-pressure regions on both Jupiter and Neptune Large oval shape high-pressure regions on both Jupiter and Neptune Most famous: Jupiter Great Red Spot Most famous: Jupiter Great Red Spot In the Southern hemisphere In the Southern hemisphere 30000 km long (when Voyager flew by) 30000 km long (when Voyager flew by) Present since first seen 300 years ago Present since first seen 300 years ago Changes in size – but never disappears Changes in size – but never disappears From Voyager 1, 1979

32. April 10, 2006Astronomy 201032 Great Red Spot Counterclockwise rotation Counterclockwise rotation Period : 6 days Period : 6 days Similar disturbances formed in 1930s on Jupiter Similar disturbances formed in 1930s on Jupiter Smaller circles near the red spot Smaller circles near the red spot Cause unknown Cause unknown Long lived because of Long lived because of absence of ground, and absence of ground, and their size their size Expected life - centuries Expected life - centuries

33. April 10, 2006Astronomy 201033 Neptune Great Dark Spot First seen in 1989 by Voyager First seen in 1989 by Voyager 10000 km long 10000 km long 17 day period 17 day period Had disappeared (faded?) in June 1994 Had disappeared (faded?) in June 1994 New dark spot seen in Nov 1994 New dark spot seen in Nov 1994 Faded by 1995 Faded by 1995 Do storms form and disappear faster on Neptune? Do storms form and disappear faster on Neptune?

34. April 10, 2006Astronomy 201034 Saturn Spots Large storms rare on Saturn Large storms rare on Saturn Appear to be connected with the seasons Appear to be connected with the seasons Spot outbreaks every 30 years or so near the equator Spot outbreaks every 30 years or so near the equator Most recently in 1990 Most recently in 1990