Copyright © 2010 Pearson Education, Inc. What is a planet? 2Q-CU6lY 2Q-CU6lY What

Copyright © 2010 Pearson Education, Inc.

What is a planet?

• http://www.youtube.com/watch?v=RQU2Q-CU6lY

• What is a planet?1. orbits the sun

2. nearly round shape because its own gravity is sufficient

3. neighborhood is cleared because its gravity is sufficient


What is a dwarf planet?

1. orbits the sun

2. nearly round shape because its own gravity is sufficient

3. neighborhood is not cleared because its gravity is not sufficient

4. Not a moon of another planet


Chapter 7The Jovian Planets

Why is Jupiter so happy?

Now we shift gears from our local rock planets to the outer gas giants.

We have in our own solar system 4 examples of each of the types of planets!


Why name planets after Greek/Roman gods and goddesses?

• Everything important got a god associated with it.• Why Roman took over Greek names?• What about dozens of other cultures and myths?• Did the Greeks think the god Jupiter was literally

in that speck of light?• Modern convention in our solar system• Rules governed by the IAU http://www.iau.org/


Mercury is the god of commerce, travel and thievery in Roman mythology. The planet probably received this name because it moves so quickly across the sky. Venus is the Roman goddess of love and beauty. The planet is aptly named since it makes a beautiful sight in the sky, with only the Sun and the Moon being brighter. Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. There are, of course, many other names for our planet in other languages. Mars is the Roman god of War. The planet probably got this name due to its red color. Jupiter was the King of the Gods in Roman mythology, making the name a good choice for what is by far the largest planet in our solar system. Saturn is the Roman god of agriculture. Uranus is the ancient Greek deity of the Heavens, the earliest supreme god. Neptune, was the Roman god of the Sea. Given the beautiful blue color of this planet, the name is an excellent choice! Pluto is the Roman god of the underworld in Roman mythology. Perhaps the planet received this name because it's so far from the Sun that it is in perpetual darkness.


For the five true planets, their element's Chinese character, hanzi(汉字 ), is also part of the names of weekdays in Japanese and Korean, complemented with Sunday and Monday.10 However, Chinese and Vietnamese number the days other than Sunday.11

The cycles of the Chinese calendar are linked to the orbit of Jupiter, there being 12 sacred beasts in the Chinese dodecannualar geomantic and astrological cycle, and 12 years in the orbit of Jupiter.

The planets in East Asia cultures


English Name

Associated element

Chinese/Japanese Characters

Chinese pinyin

Japanese romaji

Korean Name

Vietnamese Name

Old astronomical names[12]

Mercury water 水星 Shuǐxīng Suisei수성 (Suseong)

Sao ThủyChénxīng ( 辰星 )

Venusmetal/gold

金星 Jīnxīng Kinsei금성 (Geumseong)

Sao Kim, also "Sao Mai" as "morning star" and "Sao Hôm" as "evening star"

Tàibái ( 太白 )

Mars fire 火星 Huǒxīng Kasei화성 (Hwaseong)

Sao HỏaYínghuò ( 熒惑 )

Jupiter wood 木星 Mùxīng Mokusei목성 (Mokseong)

Sao Mộc Suì ( 歲 )

Saturn earth 土星 Tǔxīng Dosei토성 (Toseong)

Sao ThổZhènxīng ( 鎮星 )


Observations of Jupiter and Saturn

The Discoveries of Uranus and Neptune

Bulk Properties of the Jovian Planets

Jupiter’s Atmosphere

The Atmospheres of the Outer Jovian Worlds

Jovian Interiors

Summary of Chapter 7

Units of Chapter 7


Our mission• Understand the properties of these 4

planets• Relate their properties to their origin• Compare them to each other• Compare them to the rocky inner planets• Be able to find Jupiter in the sky, and see

its moons with binocs


Jupiter can be imaged well from Earth, even with a small telescope.

Here: Jupiter with its Galilean moons

7.1 Observations of Jupiter and Saturn

Do

you

have

bin

ocul

ars?


True-color image of Jupiter

19 jan..7.1 Observations of Jupiter and Saturn

This image is from Hubble, but much of our Jupiter knowledge is from the Galileo probe which cost $1.6b over 16 years

http://www.dailymotion.com/video/xeaio4_learn-about-the-discoveries-of-the_tech


Natural-color image of Saturn


Saturn has a thick atmosphere: why can we see it so clearly?


Cassini image of Jupiter, true color



The Cassini mission: Wow!

• Look at nasa site and wikipedia

• Here’s a nice TED talk http://www.ted.com/talks/carolyn_porco_flies_us_to_saturn.html


Uranus, in natural color. Note the absence of features and the prevalence of beauty.

23 Jan: 7.2 The Discoveries of Uranus and Neptune

How was Uranus discovered?


Neptune in natural color

7.2 The Discoveries of Uranus and Neptune

How was Neptune discovered and how was this different from every other planet so far?


The Jovian planets are large and much less dense than the terrestrial planets; Saturn is less dense than water!

7.3 Bulk Properties of the Jovian Planets

None have a solid surface at all, although all have a dense core more massive than earth? explain that!


Jovian planets, compared to Earth


Where is the snowball that started each planet?


Peculiarity of Uranus: Axis of rotation lies almost in the plane of its orbit. Seasonal variations are extreme.



Galileo spacecraft

• http://en.wikipedia.org/wiki/Galileo_(spacecraft)

• http://www.dailymotion.com/video/xeaio4_learn-about-the-discoveries-of-the_tech


Atmosphere has bright zones and dark belts.

Zones are cooler, and are higher than belts.

Stable flow underlies zones and bands, called zonal flow.

Simplified model:

7.4 Jupiter’s Atmosphere


No solid surface; take top of troposphere to be 0 km.

Lowest cloud layer cannot be seen by optical telescopes.

Measurements by Galileo probe show high wind speeds even at great depth – probably due to heating from planet, not from Sun.


Why this composition?


The Galileo probe descended into Jupiter’s atmosphere and returned valuable data. The arrow indicates its entry point.


What is difference between gas atmosphere and clouds?


Major visible features:

Bands of clouds; Great Red Spot


A hurricane that is several hundred years old, 2x the diameter of earthShown

actual size!


Two examples of smaller storms merging, first into a smaller red spot, second into existing Great Red Spot


Check: write a weather forcast for Jupiter….


The atmosphere of Saturn is similar to that of Jupiter, except that Saturn is somewhat colder and its atmosphere is thicker.

7.5 The Atmospheres of the Outer Jovian Worlds


Saturn’s atmosphere is similar to Jupiter’s, except pressure is lower.

It has three cloud layers.

Cloud layers are thicker than Jupiter’s; see only top layer.



Saturn also has large storms, and bands.



Storms near Saturn’s equator


Evidence of lightning


Enormous thunderstorm on Saturn



Rotation of Uranus can be measured by watching storms.



Neptune has storm systems similar to those on Jupiter, but fewer. The large storm system at top has disappeared in recent years.



No direct information is available about Jupiter’s interior, but its main components, hydrogen and helium, are quite well understood. The central portion is thought to be a rocky core.

7.6 Jovian Interiors


Magnetic fields of Uranus and Neptune must not be produced by dynamos, as the other planets’ fields are.

Interior structure of Uranus and Neptune, compared to that of Jupiter and Saturn:



Jupiter’s magnetosphere:

Intrinsic field strength is 20,000 times that of Earth.

Magnetosphere can extend beyond the orbit of Saturn.


So catching solar wind in a magnetic field should lead to….?


Aurorae are seen on Jupiter, and have the same cause as those on Earth – the interaction of solar wind particles with the magnetosphere.



Uranus and Neptune both have substantial magnetic fields, but at a large angle to their rotation axes.

The rectangle within each planet shows a bar magnet that would produce a similar field. Note that both Uranus’s and Neptune’s are significantly off center.



Jovians in the news

• P208. a cometary impact


Summary of Chapter 7

• Jupiter and Saturn were known to the ancients; Uranus was discovered by chance, and Neptune was predicted from anomalies in the orbit of Uranus.

• Jovian planets are large but not dense; they are fluid and display differential rotation.

• Cloud layers have light zones and dark bands; wind pattern, called zonal flow, is stable.


Summary of Chapter 7, cont.

• Storms appear with regularity; the Great Red Spot of Jupiter has lasted for hundreds of years (that we know of).

• Due to conductive interiors and rapid rotation, Jovian planets have large magnetic fields.

• Jupiter, Saturn, and Neptune radiate more energy than they receive from the Sun.


A few points in addition to know.

• Why do they hold gas? Massive, magnetosphere, and far from sun

• Why are they still losing heat? Still cooling from the big compression 4+ billion years ago

• Properties of atmospheres? Layers, clouds, rotation


How are jovians different from terrestrials to attain their structure?

• Past frost line, snowball and high gravity early

• Gas was pushed out to them

• Nevertheless, they still collected dust and debris which is buried under gas

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Copyright © 2010 Pearson Education, Inc. What is a planet? 2Q-CU6lY 2Q-CU6lY What