Formation of the Solar System

How did the Earth form? Why are planets round? All of the scientific evidence collected to date suggests that the solar system formed approximately 4.6 billion years ago, using materials that were present in a giant cloud of gas and dust known as a nebula. This nebula is so large, in fact, that our solar system occupies only a small portion of it, like a bubble in a block of Swiss cheese. The origin of this nebula, as well as how the solar system was formed within it, is the topic of this module.

Essential Questions:

How can we use the nebular hypothesis to compare and contrast the composition of the various components of the solar system, including the sun, planets, and other objects?
How can we describe the distribution of the major components of the solar system (sun, planets, asteroid belt, etc.) in terms of both relative position and actual distance?
How do we explain the difference between rotation and revolution, and describe the periods of each for the eight currently recognized planets and Pluto?

Key Words:

Accretion - the coming together and cohesion of matter under the influence of gravitation to form larger bodies
Aphelion - the point in the orbit of a planet, asteroid, or comet at which it is furthest from the sun
Atom - smallest component of an element that shares the chemical properties of the element
Compound- a substance formed when two or more chemical elements are chemically bonded together
Element- a substance consisting of atoms which all have the same number of protons (the same atomic number)
Ellipse - a regular oval shape, traced by a point moving in a plane so that the sum of its distances from two other points (the foci) is constant
Gravity- an attractive force existing between any two masses that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
Jovian Planet- a large planet composed mostly of gases, such as hydrogen and helium, with a relatively small rocky core. The gas giants of our solar system are Jupiter, Saturn, Uranus and Neptune
Molecule - a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction
Nebula - an interstellar cloud of dust, hydrogen, helium and other ionized gases
Perihelion- the point in the orbit of a planet, asteroid, or comet at which it is closest to the sun
Planetesimal- a smaller clump of gas, dust, and rocky material that may combine with other clumps to form larger masses, including planets
Revolution- the movement of one body around another body (planets around the sun, moons around planets, etc.)
Rotation- the turning of a body around an internal axis
Terrestrial Planet- terrestrial planets are Earth-like planets (in Latin, terra means "Earth") made up of rocks or metals with a hard surface, making them different from other planets that lack a solid surface. In our solar system, there are four terrestrial planets, which also happen to be the four closest to the sun: Mercury, Venus, Earth and Mars

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