Introduction to the Planets of the Solar System

Welcome to the solar system. The sun is an average, middle-aged star which is orbiting in an arm of the spiral galaxy we called the Milky Way. Unlike most stars in the Universe, which are binary systems, the sun is not accompanied by a companion star. However, the sun certainly is not alone. Orbiting the sun at varying distances are 8 planets, a few "dwarf planets,"and a collection of 173 natural planetary satellites (as of September, 2014). The Earth, occupies a spot 149,600,000 km away from the sun on average. The other objects are either closer to the sun, or much more distant, and are the focus of study for this unit.

You have finally finished a study of the Earth and Moon, and now get to move into the realm of other planets and their moons. This is your opportunity to take what you have learned about our home planet and apply that knowledge in a comparative manner to the other eight planets in our solar system.

I wish to accomplish these goals with webpages devoted to planets and moons:

  1. To have each student know the names, relative positions and sizes, and primary compositions of the nine eight planets

  2. To have each student describe the defining appearance of each planet

  3. To describe why manned space flight to each planet is difficult at best, and unfeasable for most

  4. To know which planetary moons are of greatest interest to astronomers

  5. To know some of the more significant satellite missions that gave us such wonderful images and information

Above these goals, I just want to help students develop an appreciation for the beauty and diversity of the solar system objects and appreciate how rare and precious life is on Earth, for it is presently impossible for complex life to exist anywhere else in this solar system.

Below is an introductory chart that offers a quick glance at the eight planets, in each instance compared to Earth as the standard. Pluto remains on the table, but is no longer officially designated as a planet.

Planetary Fact Sheet - Relative to Earth Values

external links ->

Mercury

Venus

Earth

Moon

Mars

Jupiter

Saturn

Uranus

Neptune

Pluto

Mass

0.553

0.815

1

0.0123

0.107

317.8

95.2

14.5

17.1

0.0021

Diameter

0..383

0.949

1

0.2724

0.533

11.21

9.45

4.01

3.88

0.187

Density

0.984

0.951

1

0.605

0.713

0.240

0.125

0.230

0.297

0.317

Gravity

0.378

0.907

1

0.166

0.377

2.36

0.916

0.889

1.12

0.059

Escape Velocity

0.384

0.926

1

0.213

0.450

5.32

3.17

1.90

2.10

0.098

Rotation Period

58.8

-244

1

27.4

1.03

0.415

0.445

-0.720

0.673

6.41

Length of Day

175.9

116.8

1

29.5

1.03

0.414

0.444

0.718

0.671

6.39

Distance from Sun

0.387

0.723

1

0.00257

1.52

5.20

9.58

19.20

30.05

39.24

Perihelion

0.313

0.731

1

0.00247

1.41

5.03

9.20

18.64

30.22

30.15

Aphelion

0.459

0.716

1

0.00267

1.64

5.37

9.96

19.75

29.89

48.02

Orbital Period

0.241

0.615

1

0.0748

1.88

11.9

29.4

83.7

163.7

248.0

Orbital Velocity

1.61

1.18

1

0.0344

0.810

0.439

0.325

0.229

0.182

0.158

Orbital Eccentricity

12.3

0.401

1

3.29

5.60

2.93

3.38

2.74

0.677

14.6

Axial Tilt

0.0004

0.113*

1

0.285

1.07

0.133

1.14

4.17*

1.21

2.45*

Surface Pressure

0

92

1

0

0.01

unknown

unknown

unknown

unknown

0

Number of Moons

0

0

1

0

2

50 + 17

53 + 9

27

13 + 1

5

Ring System

no

no

no

no

no

yes

yes

yes

yes

no

Global Magnetic Field

yes

no

yes

no

no

yes

yes

yes

yes

unknown

internal links ->

Mercury

Venus

Earth

Moon

Mars

Jupiter

Saturn

Uranus

Neptune

Pluto

The chart above has been taken and then modified for this course from:
NSSDC Planetary Home Page

Author/Curator:
Dr. David R. Williams, dwilliam@nssdc.gsfc.nasa.gov
NSSDC, Mail Code 633
NASA Goddard Space Flight Center
Greenbelt, MD 20771
+1-301-286-1258

The following pages of this Planet Unit borrow extensively from the JPL, NASA, NSSDC, LANL, and Nine Planets websites. Images and some text have been legally obtained, and where appropriate, connecting links are included, as well as any necessary credits. Other information for this Unit has been accumulated from my classroom teaching, reading, and watching educational videos and television specials.

This unit is divided into the natural manner in which the material that comprised the ancient solar nebula coalesced into the planets and moons over 4.6 billion years ago. The Inner Rocky Worlds include Mercury, Venus, Earth, and Mars. The Outer Gas Giant planets include Jupiter, Saturn, Uranus, and Neptune. Pluto, its companion moon Charon, and a few other objects are collectively called "dwarf planets." Out beyond the orbit of Neptune are two vast regions cluttered with chunks of dirty ice. These icy bodies are comets. The asteroids are chunks of rock or metals and are found between Mars and Jupiter, orbiting within Jupiter's path, or close to Earth.

Inner Rocky Worlds

Planet MercuryPlanet VenusPlanet EarthPlanet Mars

Outer Gas Giants

Planet JupiterPlanet SaturnPlanet UranusPlanet Neptune

Dwarf Planets

Pluto/Charon Ceres, Eris, Newly discovered Solar System "planets" ... Quaoar, Sedna, 10th Planet, Makemake, and Haumea

Icy Worlds

Comets

Asteroids

Asteroids

Extrasolar Planets

 

Moon Observation

BEFORE you proceed any further, you need to move to Scale Model, that will provide for you a sense of your place in space. This is a critical assignment and also very enjoyable. Upon completion of this lab exercise, you can then move forward in your study of the Solar System.

Diameter of Pluto Lab

At the end of this unit, there is a short Planet Assessment that is designed to determine if you were able to learn anything. I tried to focus on what I thought to be the most significant aspects of the planets.

***Extrasolar Planets***

As of May, 2007, there have been over 168 stars that have been discovered to be hosting planets, and a total of 221 planets have been located thus far, meaning that there are currently a lot of other stars besides our own Sun which host more than one planet. These planets are orbiting stars that are similar to our Sun, but others that are extremely unlike our Sun. For instance, astronomers have discovered planets that orbit pulsars. Many of the planets are Jupiter-like objects that are orbiting far closer to their host star than previously believed to be possible according to solar system formation hypotheses. To learn more about these extrasolar planets, click on PlanetQuest and enjoy the associated website. To learn from the most comprehensive website on extrasolar planets, go to The Extrasolar Planet Encyclopedia and click on the Interactive Catalogue.

You are strongly encouraged to follow the suggested sequence for this Unit. However, typical students do not like following directions and therefore may have come upon this page without first learning about the Earth and its Moon. If you are one of those kinds of students, please go back and complete the Earth-Moon Unit first, for it serves as the basis for comparison to all the other planets and their natural satellites. If you were one of those students who follows directions, then proceed from here to an Introduction to the Inner Rocky Worlds, or the Syllabus.


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