What is a Solar System? - Planets & Model Video

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  • 0:02 Definition
  • 0:15 Formation
  • 0:46 Objects in the Solar System
  • 2:29 Lesson Summary
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Lesson Transcript
Instructor: Jeff Fennell

Jeff has a master's in engineering and has taught Earth science both domestically and internationally.

The solar system consists of all the matter that lies within the gravitational pull of the sun. This lesson will describe the formation of the solar system along with the objects in it. At the end there will be a quiz to test your knowledge.


The solar system is the collection of all materials within the gravitational pull of the sun. All the planets, moons, asteroids, and other small stellar objects reside within the solar system.


The Solar Nebular Hypothesis states that the sun, planets, moons, and asteroids were formed at the same time, around 4.5 billion years ago from a nebula. Our Solar System formed out of the remnants of a nebula that condensed into the sun and other objects of our solar system. Gravitational pull from the large amount of mass in the sun caused hydrogen to fuse into helium, creating the birth of our sun. The plane that the planets orbit in is a result from the nebula spinning and spreading out into a flat disk.

Objects in the Solar System

The sun is by far the largest and most influential object in the solar system. Of all the mass in the solar system, 99.85% is in the sun. It provides the solar system with almost all of its energy by the process of fusion, which converts hydrogen into helium.

The solar system consists of eight planets, four inner and four outer. The inner planets are composed primarily of rock and a solid surface and are also referred to as the terrestrial planets. The outer planets are also known as gas giants and are much larger than the terrestrials. The gas giants get part of their name because they are composed primarily of hydrogen and helium gases. All of the planets orbit within a nearly flat disc called the ecliptic plane, which supports the Solar Nebula Hypothesis.

The four smaller inner planets are:

  1. Mercury
  2. Venus
  3. Earth
  4. Mars

The four outer planets are:

  1. Jupiter
  2. Saturn
  3. Uranus
  4. Neptune

Like Earth has its moon, five other planets have natural satellites orbiting them. On top of moons, each of the outer planets is encircled by planetary rings of dust and other small objects. The most visible and spectacular of these are the rings of Saturn.

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