Birth of The Sun.

Our solar system consists of the Sun, planets, moons asteroids, comets and assorted other debris left over from its formation.

The solar system was formed out of a rotating cloud of interstellar gas and dust, (known as the Solar Nebula), that was the remnant of two earlier generations of stars. It was located toward the edge of the galaxy we know as the Milky Way. Roughly 4.6 billion years ago, the nebula collapsed , possibly due to shockwaves from a nearby exploding supernova. The collapse of the nebula caused its rate of rotation to increase, and the collapsing material flattened into a disc, know as the protoplanetary disc. Matter continued to be drawn from this disc toward the centre. Energy from the collapse caused the temperature in the centre to rise and the density to increase. Eventually the temperature and density were high enough for hydrogen nuclei to start fusing to form helium and giving off energy in the form of heat and light. Our own star, the Sun, was born.

Origin of the Planets.

Not all the material in the solar nebula ended up being dragged into the forming Sun by the force of gravity. Some gas and dust remained orbiting in the protoplanetary disc. Here, dust particles stuck together into larger and larger agglomerations. Some of these dust balls were melted to form tiny rocks smaller than marbles. Known as "chondrules", these were in turn accreted, sticking together in ever larger bodies until gravitational forces could take over and keep them together. These bodies are called planetesimals. Once these planetesimals grew to around a kilometre in size, they started to attract other similar sized objects due to gravitational attraction.

At this stage, the process of accretion grew in efficiency. Many of the planetesimals continued to coalesce until they formed objects the size of Mercury or Earth. The whole process, starting from the initial collapse of the nebula and continuing through the various stages up to the formation of planets, may well have taken about 10 million years.

Not all of the planetesimals were caught up in the formation of planets. Some of them were frozen at between approximately one kilometre and tens of kilometres in size. Many of these bodies are preserved as asteroids orbiting in the asteroid belt between Mars and Jupiter.

Inner and Outer Planets.

The protoplanetary disc became hotter closer to the Sun than further out. In the hotter regions, ice evaporated. Also, gas was driven out towards the outer parts of the Solar System, a movement helped by the Solar Wind, a stream of energetic particles emitted from the Sun. As a result, planets in the inner Solar System - known as the terrestial planets - are small and rocky. But in the cold outer regions, the rocky bodies accreted ice and, because of the cold and their greater mass, could also hold on to gases such as methane, ammonia, hydrogen and helium. The result was the formation of giant gassy planets. The dwarf planet Pluto formed far out, along with many other similar frozen bodies. (Source: DK Publishing, Rocks and Minerals. Photo courtesy of Google Images.)

Well Guys,

We hope that you found that as fascinating as we did at The Emporium.

Next week's blog will be the formation of the Earth. Stay tuned!