The solar system (Sol) is one of many systems within our Universe and Galaxy, which is called the Milky Way. At its very heart is the sun, which is also classified as an ‘ordinary star’ or ‘yellow star.’
It is so close to us it fills our planet with plenty of sunlight. Trapped in its orbit by gravity are Earth and seven other planets, their moons, and millions of comets and asteroids, which in scientific terms, is classified as a ‘space minor’ body.
In our solar system, the sun is the largest part. Even the biggest planets, such as Jupiter, do not even come close to the sun’s size. It is much smaller. Jupiter contains only 99.8% of the solar system’s entire mass. Mass is defined as the amount of material an object contains, and that does not change whether the object is on Earth, on the moon, or anywhere in space, and it is nearly 1.4 million kilometres wide.
Planets such as Mercury, Venus, Earth, and Mars are nothing more than solid balls of metal. In contrast, the other planets are called gas giants. Enormous, swirling globes made mostly of hydrogen, which is the lightest element ever to exist. There is also helium, another light element which is a gas – like a big cloud on Earth.
How did this all start?
The planets of the solar system formed from gas and grains of dust and ice surrounding the newly-formed sun. The solar system was born inside a vast dark cloud of gas and dust around 5 billion years ago. Something triggered a burst of star formation in the cloud. Many people think perhaps a nearby star exploded, sending a massive shockwave rippling through the cloud. Hundreds of pockets of gas were squeezed into clumps. Their gravity pulled in more gas, making the clumps larger and denser. This made them heat up inside and start to grow. Eventually, the cores of the clumps got so hot and dense that nuclear reactions began, and they became stars – one of them being our sun.
The Phases of the Solar System:
Phase 1 (Collapsing Clump) – within the giant cloud a pocket of gas began to shrink from the shockwave, forming a supernova (exploding star) and disturbed the cloud.
Phase 2 (Spinning Disk) – as the clump shrinks, it begins to spin, turning faster and faster until it forms a disk. Its centre began to heat up.
Phase 3 (The sun is born) – nuclear reactions began in the dense centre, which began to shine at a star. The leftover matter formed a disk called the solar nebula.
Phase 4 (Planetesimals) – gravity caused the particles in the disk to clump together, forming billions of tiny planets or planetesimals.
Phase 5 (Planets Form) – the planetesimals crashed into each other, sticking together and growing into fewer and fewer planets.
Phase 6 (Migration) – the orbit of the giant planets changed. Neptune and Uranus moved further out, pushing smaller icy bodies into even more distant orbits.
Phase 7 (the Solar System) – by 3.9 billion years ago, the solar system settled down into its present pattern of planets.
The solar cycle is the cycle that the sun’s magnetic field goes through approximately every 11 years.
