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The Ordered Solar System

Ka Hana ‘Imi Na‘auao – A Science Careers Curriculum Resource Go to: www.cds.hawaii.edu/kahana

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Warm Up Questions

1. Which planet is bigger, Mercury or Jupiter ?2. Are the gas giant planets closer to the Sun

than the rocky planets (yes/no)?3. How many planets are in the Solar System?4. Is the Sun bigger, smaller, or the same size

as the Moon?5. What is the difference between the Solar

System and the Milky Way Galaxy (just one sentence) ?

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Three types of objects orbit our Sun:Three types of objects orbit our Sun:

1.1. PlanetsPlanets2.2. Dwarf Planets Dwarf Planets

• PlutoidsPlutoids

3.3. Small solar system bodiesSmall solar system bodies

Why are there only 8 planets now?

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What is a planet?

• In August of 2007 the International Astronomical Union redefined what a planet is (no official scientific definition of a "planet" existed before). A planet:

1. Is a body that orbits the sun (this definition only applies to our Solar System)

2. Is large enough for its own gravity to make it round3. And has "cleared its neighborhood" of smaller objects• So a new the category of dwarf planet was created,

which currently includes Pluto, Eris*, and Ceres**.

*Eris is the largest known dwarf planet in the Solar System and the ninth largest body known to orbit the Sun. Its distance from the Sun is 97 AU.**Ceres is the smallest identified dwarf planet in the Solar System and, because it’s the largest asteroid, the only dwarf planet in the asteroid belt.

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What is a Dwarf Planet?What is a Dwarf Planet?

• Celestial body orbiting the SunCelestial body orbiting the Sun• Massive enough to be rounded by its Massive enough to be rounded by its

own gravityown gravity• BUT has BUT has NOTNOT cleared its neighboring cleared its neighboring

region of planetesimalsregion of planetesimals• Is not a satelliteIs not a satellite

A plutoid is a dwarf planet beyond the orbit A plutoid is a dwarf planet beyond the orbit of Neptuneof Neptune

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Only 5 Dwarf Planets recognized so far but Only 5 Dwarf Planets recognized so far but there may be as many as 200there may be as many as 200

Pluto, approximatePluto, approximatetrue colortrue color

Ceres, seen throughCeres, seen through(Hubble telescope)(Hubble telescope)

Haumea, with its 2 moons,Haumea, with its 2 moons,Hi‘iaka and NamakaHi‘iaka and Namaka(Artist’s conception)(Artist’s conception)

Makemake,Makemake,(Artist’s conception)(Artist’s conception)

Eris, seen throughEris, seen through(Hubble telescope)(Hubble telescope)

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Pacific Island Names for Planetary Objects

• Haumea is the Hawaiian goddess of childbirth and fertility.

• The the moons "Hiʻiaka" and "Namaka” are named after after two of Haumea's daughters.

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Pacific Island Names for Planetary Objects

• Makemake is the creator of humanity in the mythos of the Rapanui, the native people of Easter Island. The name choice preserves the planetary object's connection with Easter.

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3. What are Small Solar System Bodies?3. What are Small Solar System Bodies?

• Neither a planet nor a dwarf planetNeither a planet nor a dwarf planet• All other objects orbiting the Sun

• All minor planets except dwarf planets• Asteroids (except Ceres, the largest)• Comets

• Not massive enough to be rounded by Not massive enough to be rounded by its own gravityits own gravity

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Terrestrial vs. Gaseous PlanetsTerrestrial vs. Gaseous Planets

TerrestrialTerrestrial

• Mercury, Venus, Mercury, Venus, Earth, MarsEarth, Mars

1.1. RockyRocky More denseMore dense

2.2. SmallerSmaller3.3. More closely spacedMore closely spaced4.4. Closer to the SunCloser to the Sun

GaseousGaseous

• Jupiter, Saturn, Uranus, Jupiter, Saturn, Uranus, NeptuneNeptune

1.1. Gaseous, has more He Gaseous, has more He and Hand H Less dense (Saturn Less dense (Saturn

would float)would float)

2.2. LargerLarger3.3. Spaced farther apartSpaced farther apart4.4. Farther from the SunFarther from the Sun

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Terrestrial Planets

Venus

Mercury

Mars

From Nick Strobel’s Astronomy Notes at www.astronomynotes.com

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Jovian Planets, or Gas Giants

Jupiter

Uranus Neptune

Saturn

From Nick Strobel’s Astronomy Notes at www.astronomynotes.com

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Do you see patterns or anomalies in these data?

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On which planet would you On which planet would you weigh the most?weigh the most?

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The Milky Way Galaxy

100,000 light years across1,000 light years thick200 billion stars

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