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Origins of the Solar System- The Solar Nebula Theory
There are lots of theories about the origin of our solar system. According to the presently accepted theory, our solar system is 5 billion years old.
Simple Outline of the Solar Nebula Theory
- Once upon a time, about 5 billion years ago, there was a very large nebula (nebula= cloud of stuff). This nebula was 25X the present size of solar system and had a temperature of about 50 K.
- Gravity pulled particles together. As the size increased, temperature increased. Most of the material clumped up in center, forming a proto-sun.
- Eddy currents formed at different distances, resulting in proto-planets
- Close to center, the high melting point elements formed inner planets: Mercury, Venus, Earth, and Mars, pictured below.
5. Far away, the low melting point materials formed outer planets: Jupiter, Saturn, Uranus and Neptune.
6. At a temperature of about 10 million K in the center, thermo-nuclear fusion began in sun and blew away most debris.
The Asteroid Belt
The Asteroid Belt is in orbit between Mars and Jupiter. It is very sparsly populated, and spacecraft can pass through without any problems. It contains thousands of objects, but the combined mass of these objects is smaller than the Earth's mass. The image below shows the Asteroid Belt's place among the planets.
The Kuiper Belt
The Kuiper belt occupies the Trans-Neptunian region, the area beyond Neptune that remains largely unexplored. It is similar to the Asteroid Belt, but its objects are mainly made of ice.
The image below shows a plot of known Kuiper belt objects in relation to the outer planets.
The Oort Cloud
There might to be more to this thing than its awesome, science-fictiony name, but if there is, we haven't found it yet. This is a hypothetical cloud of comets. Pretty cool, right? The Oort cloud is believed to be a spherical cloud that is the source of all of the long-term comets that enter the solar system. It is considered to be the "outer bounds" of the Solar System.
Only four known objects are considered to be part of the Oort Cloud. Below I've included a drawing of what the Oort Cloud is believed to look like.
More Astronomy Info
- Astronomy 101. Phases of the Moon, Lunar Eclipse, Solar Eclipse, and More.
Astronomy basics that will help you navigate through the night sky. Learn how solar and lunar eclipses work, what causes the phases of the moon, along with other very basic astronomical knowledge. Included are beautiful photos and diagrams.
All photos were taken from Wikimedia commons.