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Lesson 19The Jovian Planets

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

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The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

The Planets So Far

• The outer planets are divided into

two sub-categories:

• The Jovians

– Jupiter and Saturn

• The Ice Giants

– Uranus and Neptune

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

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The Jovians

• Are mostly gases (H, He, H2O, CH4, NH3); the

rest = ice + rock

• Have no solid surface: gases --> solid at high

pressure

• Have ring systems and many moons

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

79 ceti b – an exoplanet the size of

Saturn

The Jovians

• Form faster, and in a different way, compared

to terrestrial planets: large enough to

accumulate gas directly from the solar nebula

• They are far from the Sun (in the case of the

solar system)

• So far, most extrasolar planets are gas giants,

but they are all close to their parent star

(why?)

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The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Some exoplanets…

Jupiter Facts

• Jupiter’s diameter is 10x that of the earth’s

• Jupiter’s mass is 300x that of the earth’s

• Jupiter’s gravity is 2.36x that of the earth’s

– If you weigh 180 lbs on earth’s surface, at the

cloudtops on Jupiter you would weigh 426 lbs.

• Jupiter orbits at roughly 5 AU.

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

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Jupiter Facts

• All we can see on Jupiter are clouds

– These clouds are in bright zones and dark belts

– These are banded due to the rapid rotation of Jupiter.

• Jupiter rotates in roughly 10 hours, though each

band rotates at different speeds.

• As you descend into Jupiter, the atmosphere

transitions directly from gas to supercritical

liquid, meaning that there is no “surface” on

Jupiter.

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Jupiter Facts

• Jupiter should be purely white.

– Its clouds are primarily water and ammonia, both

of which form white clouds…

• They aren’t due to organic compounds that

stain the cloud layers.

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The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Three years ago, one entire band

vanished….

Jupiter Facts

• Jupiter gives off more energy than it recieves

from the sun.

– Roughly 1.67x more than it gets.

– Possibly due to heat generated when the planet

formed

– Or it could be due to radioactive decay

• That’s the process that keeps the earth nice and toasty!

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

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Jupiter Facts

• The winds that give Jupiter its storms and

bands run deep…as far down as we can

measure, in fact

• This is due to the huge amount of energy from

the core

• If Jupiter was about 80x heavier, it would have

become a dwarf star.

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Taken by Cassini:

Jupiter Observations

• Pioneer 10 flew by Jupiter on December 1, 1973.

• Pioneer 11 flew by Jupiter on December 1, 1974.

• Voyager 1 flew by Jupiter on March 5, 1979.

• Voyager 2 flew by Jupiter on July 9, 1979.

• Ulysses, studies the poles of the Sun. Jupiter flyby February 8, 1992.

• Galileo Orbiter/Atmospheric Probe - 1995 – 2003.

• Cassini – flew by December 30th, 2000

• New Horizons – flew by February 28th, 2007

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Jupiter Observations

• Galileo atmospheric probe of Jupiter’s atmosphere - December 7th, 1995

• Depth of measurements ~200 km

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Taken by Cassini:

Jupiter Observations

Upcoming:

• Juno – launched in 2011, arrives in 2016

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• Jupiter, with its dark belts (where gases move down into the interior), and light zones (where gases move upwards).

• Also visible is the Great Red Spot, a huge hurricane that has been observed from Earth for ~ 350 years, and other more or less temporary surface features

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Belt versus Zone

The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Jupiter Cloud Structure

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The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Jupiter Cloud Structure

Jupiter Observations

Some features in Jupiter’s dynamic atmosphere change just like weather on Earth. The 2 images are 10 hours apart.

Jupiter Observations

Winds at top of atmosphere – travel in opposite directions at different latitudes

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The great red spot

The great red spot

A giant cyclone. Twice as big as earth. Existed for AT LEAST 350 years.

The white spots

Other cyclones (usually white) also exist, but none more than a few months or years

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The rings

Voyager discovered rings around jupiter in 1978

The rings

Second only to Saturn's rings in size or complexity

182,000 km

Moons inside

ring system

Strength of the magnetic fields of the

planets.

Jupiter has by far the strongest magnetic field, because its interior is made of an excellent electric conductor (liquid metallic hydrogen), and because the planet rotates around its axis faster than any other (once in 10 hours).

A strong refrig-

erator magnet

has a magnetic

field of 100 gauss

Object

Strength of field

(gauss)

Inclination of magnetic

axis relative to rotation

axis (degrees)

Mercury 0.003 <10

Earth 0.35 12

Jupiter 4.225 11

Saturn 0.2 0.7

Uranus 0.1 – 1.1 60

Neptune 0.3 59

The strengths are given at the surfaces of mercury and earth, and at the

cloud tops of the outer planets. Venus and mars have no detectable

magnetic fields.

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The Planets So Far

• Four Inner Planets

– All found Inside of the asteroid belt

– Mercury, Venus, Earth, Mars

• Four Outer Planets

– All found outside of the asteroid belt

– Jupiter, Saturn, Uranus, Neptune

Aurora at poles of Jupiter – show that Jupiter

has a strong magnetic field

Jupiter summary

Saturn: The ringed planet

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Saturn: The ringed planet

• Saturn was the Roman counterpart of the greek titan Kronos, father of gods like Jupiter (Zeus). He was also the god of agriculture.

• The ancient symbol of Saturn resembles a sickle. It is also the alchemical symbol for the element lead.

• Saturday was named after Saturn (dies Saturni, or day of Saturn).

Galileo Galilei

• Galileo first observed the rings of Saturn through his telescope in 1610.

• He first described them as “handles”. Later, because of the aberrations in his telescope, he thought they were blurred twin moons.

Christiaan Huygens

• Making his own telescope of far better quality than Galileo’s, the Dutch scientist Christiaan Huygens discovered in 1655 the first, and largest, moon of Saturn: Titan.

• Now a popular scientific tool, telescopes can be used to observe the rings of Saturn.

• The image below shows drawings of Saturn’s rings, made by several authors, from Galileo, Scheiner, Hevelius and Huygens, among others.

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Christiaan Huygens

• In 1659, Huygens became the first to correctly interpret what Galileo’s mysterious “handles” were – a ring system.

• He also provided the first theory for the different shapes of the rings, as seen from Earth.

Giovanni Cassini

• Giovanni Cassini was contemporary to Huygens. In 1665 he discovered a gap in the rings of Saturn. It is still called the Cassini Division.

• He discovered four moons of Saturn:

Iapetus, Rhea, Dione, and Thetys.

Voyagers 1 and 2

• Voyagers 1 and 2 are spacecraft which have studied Saturn and returned incredible images.

• False color image from Voyager 2 (ultraviolet, violet and green), taken at a distance of 43 million km, in July 1981.

• Voyager 1 photo taken at a distance of 5.3 million km, in November 1980.

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Multi-wavelength Saturn

• In September 2003, the Hubble Space Telescope took images of Saturn in ultraviolet, visible, and infrared light:

Ultraviolet

Infrared

Visible

Cassini/Huygens

• On the 1 July 2004, the NASA/ESA mission Cassini/Huygens reached Saturn’s orbit, becoming the first “visitor” to Saturn since Voyager 2.

• Huygens was the European Space Agency (ESA) lander , which became the first man-made object to ever land on another moon of the Solar System – Titan.

The size of Saturn

• The planet Saturn is so large that it would fit neatly

between the Earth and Moon:

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Saturn’s inner

layers

Broken up into Four layers:

• Mantle (composed of water, ammonia, and methane ices)

• Molecular hydrogen

• Metallic hydrogen

• Rocky core

More Facts

• Saturn contains the most

hydrogen of any of the

planets

• That makes it the least

dense

• It would float in water if

there was an ocean big

enough

More Facts

• Saturn rotates so fast that it has the largest equatorial bulge of any planet– 7000 miles … roughly 10% of its total diameter.

• Its rings are completely separate from the rest of Saturn

• The total mass of the rings are roughly equivalent to the moon Minmas.

• The rings stem from a medium sized moon being torn apart due to tidal friction.

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Storms in Saturn

• In the South Pole of Saturn there are several vortexes, which form rings within rings. These are “locked” in the Pole.

• One of the most curious storms is in the North Pole, a hexagon shaped storm, revealed in this infrared image from Cassini. It is a clearing in the clouds, which extends deep below the visible clouds (about 75 km in depth).

Storms in Saturn

• Between February and March 2004, before its arrival at Saturn, Cassini observed the merger of two storms.

• The top four frames span 26 days, while the bottom four span only four days.

Aurorae

• Saturn has a magnetosphere similar to the Earth, which also reacts with solar activity.

• One of the most beautiful of these interactions are the aurorae, visible in ultraviolet in these images.

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Ring features

• The rings of Saturn are the most prominent and distinctive feature of this planet.

• The image above is a mosaic of 45 different images, taken by the Cassini spacecraft on November 2008, and shows their main sections.

C ring

17500 km

B ring

25 580 km

A ring

14 580 kmCa

ssin

i

div

isio

n

65 700 km

F r

ing

Multiple Rings!

Encke GapCassini Division

E Ring extends to 7.5 Saturn radii from cloud top

Ring features

• Spokes are dark patches seen in the rings, and are thought to be dust particles which scatter sunlight.

• Depending on the observing angle, they can appear darker (low angles, image below), or brighter (high angles) than the rings.

• The rings are formed by elongated clumps of ice, continuously forming, only dispersing when they bump into each other.

• The ice in the clumps rarely crashes, rather moving from one clump to the other.

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Saturn summary

Saturn summary