The Solar System (Part 1)
The solar system is our cosmic neighbourhood, a tiny yet remarkable part of the Milky Way Galaxy. It was born about 4.6 billion years ago, when a giant cloud of gas and dust collapsed under its own gravity. At the centre of this swirling disk, the Sun ignited, while the remaining material clumped together into planets, moons, asteroids, and comets.
Today, the solar system stretches nearly two light-years across and is held together by the Sun’s immense gravity. At its heart lies the Sun, surrounded by eight planets, their moons, dwarf planets such as Pluto, and countless smaller bodies.
The four inner planets, Mercury, Venus, Earth, and Mars, are small and rocky, often called terrestrial planets because of their solid surfaces. Beyond them lie the outer planets, Jupiter, Saturn, Uranus, and Neptune, massive worlds of gas and ice, each with complex systems of rings and moons.
At the farthest reaches orbit the dwarf planets, such as Pluto, Eris, and Haumea. These icy bodies are reminders that the solar system is still full of hidden worlds waiting to be explored.
Did You Know? If the solar system were shrunk to the size of a football field, Earth would be no larger than a pea, while Pluto would orbit just outside the stadium walls.
The Sun – Our Star
The Sun is not only the largest object in the solar system, it contains more than 99% of its mass. It is a star, a giant sphere of hot plasma powered by nuclear fusion in its core. This fusion converts hydrogen into helium, releasing the energy that lights and warms our world.
The Sun has distinct layers, each playing a role in how its energy reaches us:
-
At the core, temperatures reach about 15 million °C, and nuclear fusion takes place.
-
The radiative zone is where energy slowly leaks outward as photons of light, taking thousands of years to travel.
-
The convective zone is turbulent, with hot gases rising and cooler ones sinking in great cycles.
-
The photosphere is the Sun’s visible “surface,” glowing at about 6,000 °C.
-
Above it, the chromosphere appears as a thin reddish layer during eclipses, while the outermost corona stretches millions of kilometres into space, visible as a pale halo during a total solar eclipse.
The Sun is currently a main sequence star, about halfway through its stable life. Billions of years from now, it will swell into a red giant, engulfing the inner planets, before shrinking into a dense white dwarf, a glowing ember that will cool slowly for eternity.
Short youtube video: https://www.youtube.com/watch?v=2HoTK_Gqi2Q
For Earth, the Sun is everything. It provides the light for photosynthesis, the heat that keeps water liquid, the energy that drives weather and climate, and even a shield, as its magnetic field helps protect us from harmful cosmic rays.