Exploring Our Solar System: A Journey Through the Planets 🌌 Our solar system is a cosmic masterpiece formed around 4.6 billion years ago , when a giant spinning cloud of gas and dust—known as the solar nebula —collapsed under gravity and flattened into a protoplanetary disk sciencedirect.com +8 science.nasa.gov +8 en.wikipedia.org +8 . At its core, the Sun ignited through nuclear fusion, pulling in over 99% of the system’s mass , while the remaining material coalesced into planets, moons, asteroids, comets, and dwarf planets science.nasa.gov +3 science.nasa.gov +3 gelogia.com +3 . 🌞 1. The Sun A G-type star at the center, the Sun sustains life on Earth via its heat and light. Its intense core, heated to 15 million °C , powers fusion—turning hydrogen into helium . It's encircled by the heliosphere , which shields the planets from cosmic radiation. 🌍 2. The Rocky Inner Planets Closest to the Sun are Mercury , Venus , Earth , and Mars . These are small, rocky worlds , ...