Introduction to the Solar System Chapter 6

The Sun

Mass in Solar System Sun99.8% Jupiter 0.1% Comets 0.05% All Other Planets 0.04% Earth %

Solar System Temperatures PlanetDistanceTemperature (top of atmosphere) Mercury 0.38 AU450 K Venus 0.72 AU330 K Earth 1.00 AU280 K Mars 1.52 AU230 K Jupiter 5.20 AU120 K Saturn 9.54 AU 90 K Uranus19.22 AU 60 K Neptune30.06 AU 50 K Pluto39.5 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 in Workbook)

The image at right shows a picture of the Sun. The dark spots located on this image are sunspots. How does the size of Earth compare to the size of the sunspot that is identified on the right side of the image of Sun? A) Earth and the sunspot are about the same size. B) The sunspot is much larger than Earth. C) The sunspot is much smaller 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

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/cm 3 ) (water = 1 gm/cm 3 ) 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 Mars The Asteroid Belt

Asteroids Small rocky bodies –High density (3-5 gm/cm 3 ) –Usually not round –Primitive composition (oldest bodies in solar system) Asteroid Belt –Found between Mars and Jupiter –Probably a failed planet?

The Jovian Planets

Jovian Planets Jovian = Jupiter-like –Jupiter –Saturn –Uranus –Neptune Large, massive Many moons Far from Sun

Jovian Planets Low density (1 gm/cm 3 ) No obvious surface Atmosphere –Mostly hydrogen and helium –Other gases (methane, ammonia) may form ices

The Outer Solar System Comets Kuiper Belt and Oort Cloud

The Outer Solar System Pluto –Small, icy –Low density –Little or no atmosphere Kuiper Belt –Small icy bodies Is Pluto really the largest Kuiper Belt object? –Distributed in disk-like geometry (in plane of solar system) –Distance: ,000 AU Oort Cloud –Small icy bodies –Distributed spherically around solar system –Distance: 10, ,000 AU