What is a simple subject?

The sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The sun radiates this energy mainly as light, ultraviolet, and infrared radiation, and is by far the most important source of energy for life on Earth.

Its diameter is about 1.39 million kilometers (864,000 miles), or 109 times that of Earth, and its mass (about 2×1030 kilograms) accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the sun's mass is hydrogen, while the rest is mostly helium. The remaining 1.69% (which nonetheless equals 5,628 times the mass of Earth) consists of heavier elements including oxygen, carbon, neon, and iron.

The Sun formed about 4.6 billion years ago from the gravitational collapse of a region within a large molecular cloud. Most of the matter collected in the center, while the rest flattened into an orbiting disk that became the Solar System. The central mass became increasingly hot and dense, eventually initiating nuclear fusion in its core. It is estimated that the sun will burn for another 5 billion years.

Here's a breakdown of key concepts:

• Solar System: The sun is the center of our solar system.
• Plasma: The sun is primarily composed of plasma.
• Nuclear Fusion: The sun generates energy through nuclear fusion.
• Earth: The sun is essential for life on Earth.
• Hydrogen: The sun is primarily composed of Hydrogen.
• Helium: Helium is the second most abundant element in the Sun.