The Formation of the Solar System
Based on supporting evidence, scientists theorize that an extremely hot and dense state of matter and energy suddenly emerged from the singularity during the "Big Bang" around 13.7 million years ago. As part of the Big Bang Theory, scientists believe that all the matter and energy necessary to form everything in our universe emerged from this singularity. About 4.6 billion years ago, nestled in an outer arm of the Milky Way Galaxy, a tiny portion of this matter formed into a spiraling cloud of superheated hydrogen gas and dust, which scientists call a solar nebula. This cloud began to slowly condense as a result of gravity. Eventually, the collapse of the nebula began to accelerate and the cloud became most dense at the center. This dense center eventually became the Sun, and the remaining material surrounding it formed the planets and other stellar objects as it accumulated over time.
While scientists were not present 4.6 billion years ago, evidence through observations and experiments have led to the development of the Solar Nebula Theory based on similar processes occurring in other areas of space. In this interactivity, click on each of the events to learn more about each step in the process that astronomers believe formed the Solar System. Click the player button to begin.
View a printable version of the interactivity.
To find out more about the possible formation of the Solar System, view the video NOVA scienceNOW: Origins of the Solar System from eMediaVA℠. As you view the video, make note of the data that scientists use to research how the Solar System formed and to support the Solar Nebular Theory.
The Habitable Zone and Exoplanets
Kepler-16b, the first planet known to
definitively orbit two stars
Earth is located in the habitable zone, meaning the planet is located in a perfect location from the Sun. The habitable zone is also known as the the Goldilocks zone, after the popular children's' tale in which a child seeks food and furniture that is "just right." The planet Earth is not located too far away from the Sun, or it would be too cold to sustain life. If the planet was located closer to the Sun, then it would be too warm and would not support liquid water. This zone does not just exist around the Sun in this Solar System. It also exists around other stars throughout the universe. Astronomers are continuing to study these habitable zones around stars in a quest to find other planets (like Earth) that are in spots that are "just right." Space telescopes assist with the search for habitable areas.
Image courtesy of NASA
An artist's depiction of Kepler 22b, an Earth-like
exoplanet in the habitable zone of a Sun-like star
Exoplanets are planets that are outside of the Solar System. As of March 2014, almost 1800 of these planets had been discovered. Scientists believe that there are at least 100 billion planets in the Milky Way Galaxy, which means that there is a ratio of one planet to one star in the galaxy. Scientists theorize that there could be as many as 40 billion Earth-sized planets located in the habitable zones of stars throughout the Milky Way Galaxy. Most of these exoplanets have been identified by the Kepler Space Telescope, which launched in 2009.
The Formation of the Solar System Review
Now that you have explored how scientists believe the Solar System formed, check your knowledge in this non-graded activity. Read each question, and select the appropriate answer. Then, click SUBMIT to check your response. Click the player button to get started.