Astronomy and Planets

Our Solar System

The Sun sits at the center of our solar system. Its gravity pulls everything into orbit, including eight planets, dwarf planets, moons, asteroids, and comets. The planets travel in nearly circular paths called orbits. Each planet has its own speed and distance from the Sun, which creates a wide variety of environments.

The Inner Planets

The four planets closest to the Sun are called the inner, or terrestrial, planets.

• Mercury – Smallest planet and closest to the Sun. It has extreme temperature changes because it has no atmosphere to hold heat.
• Venus – Similar in size to Earth but covered by thick clouds of sulfuric acid. Its surface is hotter than Mercury’s.
• Earth – The only planet we know that supports life. It has liquid water, a protective atmosphere, and a magnetic field.
• Mars – Known as the “Red Planet” because of iron oxide dust. It has the tallest volcano and the deepest canyon in the solar system.

These planets are made of rock and metal, and they have solid surfaces you could, in theory, stand on.

The Outer Planets

Beyond the asteroid belt lie the giant, or gas, planets.

• Jupiter – The largest planet, with a famous Great Red Spot that is a huge storm. It has at least 79 moons.
• Saturn – Recognized by its bright rings made of ice and rock particles. It also has many moons, including Titan, which has a thick atmosphere.
• Uranus – Rotates on its side, giving it extreme seasons. Its blue‑green color comes from methane gas.
• Neptune – The farthest known planet, with strong winds that can reach 2,000 km/h.

These worlds are mostly hydrogen and helium. They do not have solid surfaces; instead, you would sink deeper into thick layers of gas.

Why Planets Matter

Studying planets helps us understand how worlds form and evolve. By comparing Earth to its neighbors, scientists learn what makes a planet habitable. Missions to Mars, Jupiter’s moons, and even distant dwarf planets teach us about climate, geology, and the potential for life elsewhere.

Exploring the solar system also inspires new technology. Rockets, telescopes, and space probes all began as ideas to reach these distant planets. The more we discover, the better we can protect our own planet and imagine humanity’s future among the stars.