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The Jovian Planets Huge worlds, heavily mantled in gas at the time of the

formation of the Solar System.

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Composition of the Jovian Planets Jupiter and Saturn attracted so much gas gravitationally

during formation that the have a composition that largely matches the Sun

− Mostly hydrogen, some helium, and a a tiny fraction of the other elements.

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Composition of the Jovian Planets Jupiter and Saturn attracted so much gas gravitationally

during formation that the have a composition that largely matches the Sun

− Mostly hydrogen, some helium, and a a tiny fraction of the other elements.

- Uranus and Neptune are also dominate by Hydrogen and Helium, but not to the degree that Jupiter and Saturn are.

- The significant portion of their mass likely made up by water leads to Uranus and Neptune being called “ice giants”

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Composition of the Jovian Planets Under the immense pressure of the “atmosphere” hydrogen

and helium behave more like liquids in the interior. Only the outermost layers are recognizable as “atmosphere”

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Jovian Planet Surfaces There aren't any... The cloudtops provide an apparent

surface, but beneath is nothing but gas of increasing density.

− The “cartoon” cores do not represent a surface either (in the same way as you would not regard the Earth's core as a “surface”).

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Jovian Cloud Composition Jovian planets, particularly Jupiter and Saturn, have “cloud

decks” of different composition.

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Jovian Cloud Composition The highest (and whitest) clouds are ammonia. Next deepest is ammonium hydrosulfide, and deeper still is

water.

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Jovian Cloud Composition The highest (and whitest) clouds are ammonia. Next deepest is ammonium hydrosulfide, and deeper still is

water.

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Jovian Cloud Composition For Uranus and Neptune it is cold enough that the high cloud

decks are frozen methane.

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Jupiter vs. Saturn Jupiter's cloud features are more sharply defined than

Saturn's because Saturn's cloud decks form lower in the atmosphere.

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Learning about the Jovian Planets Earth-based telescopes can provide plenty of analytic

information about atmospheric composition and bulk weather on Jovian worlds but the view is fuzzy because of our distance.

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Learning about the Jovian Planets Going there makes a huge difference....

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Voyager Two Voyager spacecraft were launched in 1977 and arrived at

Jupiter in 1979. One of the two visited Jupiter, Saturn, Uranus and Neptune – the last in 1989.

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Visits to Jupiter Pioneer flyby(s) - 1973/4 Voyager flyby(s) - 1979 Galileo orbiter - 1995 Cassini flyby - 2000 (on the way to orbit Saturn in 2004) New Horizons flyby – 2007 (on the way to fly by Pluto in 2015)

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Visits to Jovian Planets Jupiter

− Pioneer 10 and 11

− Voyager 1 and 2

− Galileo Orbiter

− Cassini (boost to Saturn)

− New Horizons (boost to Pluto)

− Juno (in transit – arrival 2016)

Saturn

− Pioneer 10 and 11

− Voyager 1 and 2

− Cassini orbiter

Uranus and Neptune

− Voyager 2

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Don't Forget the Moons These spacecraft also provided detailed views of numerous

satellites of these Jovian worlds.

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Rapid Rotation All Jovian planets rotate rapidly. Jupiter completes a rotation

in just under 9 hours.

− The rapid spin leads to significant “flattening”

− The shape of the planets gives away information about the cores.

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Rapid Rotation Rapid rotation also leads to

banded atmospheric circulation – belts and zones.

− These bands correspond to terrestrial high and low pressures systems

− sinking and rising atmosphere respectively.

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Rapid Rotation Rapid rotation also leads to

banded atmospheric circulation – belts and zones.

− These bands correspond to terrestrial high and low pressures systems

− sinking and rising atmosphere respectively.

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Hadley Circulation

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Oval Storms on Jupiter The scale of the Great Red Spot

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The Great Red Spot The scale of the Great Red Spot

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Planetary Magnetic Fields

Liquid Metal Core?

Rapid Rotation?

Strong Magnetic Field?

Mercury No No No

Venus Yes No No

Earth Yes Yes Yes

Mars No Yes No

Jupiter Yes Yes, Yes Huge

Saturn Yes Yes, Yes Huge

Uranus/Neptune

Salty slush?

Yes Yes

Rapid rotation combined with a liquid metallic interior leads to the generation of an intense magnetic field

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Interaction with the Solar Wind Planetary magnetic fields shield planets from the solar wind

and cause energetic particles to interact with the planet's atmosphere causing auroral emission.

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Magnetospheres Planetary magnetic fields shield planets from the solar wind

and cause energetic particles to interact with the planet's atmosphere causing auroral emission.

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Jupiter's Immense Magnetic Field

Rapid rotation combined with a liquid metallic interior leads to the generation of a magnetic field so strong that its influence extends beyond Saturn's orbit.

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Aurorae Planetary magnetic fields guide high-energy solar wind particles

to the planetary poles

− The interaction of these particles with atmospheric gases makes the gases emit spectral line radiation causing aurorae.

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Jupiter's Aurora

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Aurorae on Earth The aurora borealis/australis (also known as the “northern

lights” is typically a phenomenon observed at northerly latitudes.

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Earth's Aurora

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Earth's Aurora

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Why isn't Jupiter a Star? It's made of the same mix of elements as the Sun. It's similar in size.

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Why isn't Jupiter a Star? Jupiter may be 1/10th the diameter of the Sun, but it has

1/1000th the mass of the Sun – therein lies the key difference.

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What Keeps the Sun Shining The Sun has maintained its current luminosity of

400,000,000,000,000,000,000,000,000 (4x1026) Joules/second for the past 4.6 billion years.

− A 100 Watt lighbulb consumes 100 Joules/second

− World energy demand is about 1 trillionth of this rate.

The Sun emits enough energy every second to supply the world for a million years.

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What Keeps the Sun Shining The Sun has maintained its current luminosity of

400,000,000,000,000,000,000,000,000 (4x1026) Joules/second for the past 4.6 billion years.

− A 100 Watt lighbulb consumes 100 Joules/second

− World energy demand is about 1 trillionth of this rate.

The Sun emits enough energy every second to supply the world for a million years.

Where does this energy come from?− Chemical burning last only 10,000 years. Gravitational

contraction would supply energy for 10 million years.

The Answer

E = mc2

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E=mc2

Matter and Energy are interchangeable quantities, if you have the right tools.

Einstein's famous formula gives the conversion rate.

− c is the speed of light (3x108 meters/sec) – a huge number... squared here.

− a small amount of matter represents a huge amount of energy.

A penny has a mass of 2.5 grams− converted to energy it could keep a 100

watt light bulb shining for 100,000 years.

− or supply the world's energy needs for 20 seconds.

− or lay waste to a large city....

This 100% conversion is possible if you are able to mix equal quantities of matter and antimatter.

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E=mc2 at 0.7% Efficiency Hydrogen under pressure and heated to 10's of millions of

degrees will fuse to form Helium.

− High temperatures get protons moving fast enough to overcome the repulsive force of their like charges.

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E=mc2 at 0.7% Efficiency At these high speeds the protons can get close enough for the

strong nuclear force to take over and fuse them together.− By the end of the process 0.7% of the mass has

disappeared.

− This small efficiency is enough to have kept the Sun shining for 4.6 billion years.

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A Hot Solar Interior Just as when you descend from a mountain it gets hotter as

you go deeper into the Earth's atmosphere, the crushing pressure of the Sun's outer layers make the Sun's interior immensely hot.

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A Hot Solar Interior The expected central temperature of about 15 million degrees

is just right for thermonuclear fusion to occur.− Jupiter comes up quite short, reaching a central temperature

of a few 10's of thousands of degrees.

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Solar Neutrinos

Each fusion of a pair of protons to form a deuteron produces an energetic neutrino.

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Solar Neutrinos

Atoms are mostly empty space. Squeeze all the “space” out of the Earth and it would fit in Scott Stadium (you would fit in the head of a pin)

NO!

Yes!

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Solar Neutrinos

Neutrinos interact weakly even with protons and neutrons.

- When they are produced in the Sun the fly out of the center of the Sun unimpeded at the speed of light.

– - A trillion (1012) of them are passing through you every second right now.

–

Yes!

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Solar Neutrinos

Yes!

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Energy Still Leaking out of the Interior Jupiter as a thermal (infrared) source

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How Big for Fusion? Jupiter would have had to have been about 80 times more

massive to get hot enough internally to fuse hydrogen into helium.

− We find examples in interstellar space of objects that formed like stars that didn't reach this threshold – Brown Dwarfs.

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How Big for Fusion? Jupiter would have had to have been

about 80 times more massive to get hot enough internally to fuse hydrogen into helium.

− We find examples in interstellar space of objects that formed like stars that didn't reach this threshold – Brown Dwarfs.

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Massive Extrasolar Planets Many of the extrasolar planets being found today are many

times the mass of Jupiter. Planets this large will still exhibit substantial “leftover”

infrared luminosity.

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Massive Extrasolar Planets Many of the extrasolar planets being found today are many

times the mass of Jupiter. Planets this large will still exhibit substantial “leftover”

infrared luminosity – the younger the brighter – ultimately enabling their direct detection.

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Finding Them

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Finding Them

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Finding Them