Introduction to the Solar System

Chapter 6

The Sun

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Mass in Solar System

Sun 99.8%

Jupiter 0.1%

Comets 0.05%

All Other Planets 0.04%

Earth 0.0003%

Solar System TemperaturesPlanet Distance Temperature

(top of atmosphere)

Mercury 0.38 AU 450 K

Venus 0.72 AU 330 K

Earth 1.00 AU 280 K

Mars 1.52 AU 230 K

Jupiter 5.20 AU 120 K

Saturn 9.54 AU 90 K

Uranus 19.22 AU 60 K

Neptune 30.06 AU 50 K

Pluto 39.5 AU 40 K

45 F

-390 F

350 F

Comparative Planetology

• Categorize planets by properties

• Compare similarities and differences

• Ask: What physical processes can explain these properties?

Planet Orbits

• Orbits aligned in same plane (the ecliptic)– Explains why planets always found in Zodiac– Pluto’s orbit tipped the most (17 degrees)

• All planets orbit Sun counter-clockwise• Planets rotate counter-clockwise

– except Venus

• Rotation axis roughly perpendicular to orbit– except Uranus and Pluto

Planet Orbits

The Scale of the Solar System

Workbook Exercise: “Sun Size” (p. 63-65 in Workbook)

The image at right shows apicture of the Sun. The darkspots located on this imageare sunspots. How does thesize of Earth compare to thesize of the sunspot that isidentified on the right side ofthe image of Sun?

A) Earth and the sunspotare about the same size.B) The sunspot is muchlarger than Earth.C) The sunspot is muchsmaller than Earth.

Sunspot

If you were constructing a scale model of the solar system that used a Sun that was the size of a basketball (approximately 12 inches in diameter), which of the following lengths would most closely approximate the scaled distance between Earth and the Sun?

A) 3 feet (length of an outstretched arm)B) 10 feet (height of a basketball goal)C) 100 feet (height of an 10 story building)D) 300 feet (length of a football field)

Let’s consider a scale model of the Solar System!

The Terrestrial Planets

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Terrestrial Planets

• Terrestrial = Earth-like– Mercury

– Venus

– Earth (and Moon)

– Mars

• Small, low mass• No large moons (except Earth)

– Mars has two small ones…

• Close to Sun

Terrestrial Planets• Rocky Surface

– High density (3-5 gm/cm3) (water = 1 gm/cm3)

• Geologic Activity (volcanoes, continental drift)– Present on larger planets (Earth and Venus)

– Absent on smaller planets (Moon, Mercury, and Mars)

• Atmosphere– Little hydrogen and helium

– Mostly carbon dioxide (Venus and Mars) or nitrogen (Earth)

– Smaller planets have no atmosphere (Mercury, Moon)

Asteroids

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Mars

The Asteroid Belt

The Jovian Planets

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Jovian Planets

• Jovian = Jupiter-like– Jupiter– Saturn– Uranus– Neptune

• Large, massive• Many moons• Far from Sun

Jovian Planets

• Low density (1 gm/cm3)

• No obvious surface

• Atmosphere– Mostly hydrogen and helium– Other gases (methane, ammonia)

• may form ices

The Outer Solar System

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Comets

Kuiper Belt and Oort Cloud