The sun formed from a giant, spinning cloud of gas and dust called a nebula. It is about 4.5 to 4.6 billion years old. The sun is a yellow dwarf, a medium-size kind of star, and there are billions of stars like it in the Milky Way galaxy. As of November 2026, scientists predict the sun is a little less than halfway through its lifetime. Deep in its core, which is about 27 million degrees Fahrenheit, nuclear fusion turns hydrogen into helium. This makes the sun's energy.

The sun's diameter is about 865,000 miles, or 1.4 million kilometers. That is about 100 times wider than Earth, or 109 times more exactly. It would take 1.3 million Earths to fill the sun, and it would take more than 330,000 Earths to match its mass. The sun is a huge ball of gas, mostly hydrogen and helium, so you could not stand on its surface. Its energy travels to Earth at the speed of light, and the light takes about 8 minutes to get here.

The sun spins, but not all of it at the same pace. At the equator the sun rotates once about every 25 Earth days, but at its poles it rotates once every 36 Earth days. The sun is also on the move. Every 230 million years, the sun and the solar system it carries with it make one orbit around the center of the Milky Way. The sun's gravity holds the solar system together. The sun also sends out a steady stream of charged particles called the solar wind, which fills the heliosphere, a huge bubble of charged particles around the solar system.

Sunspots are dark, cooler spots on the sun, and they typically stretch 1,000 to 100,000 miles across. The number of sunspots goes up and down in a cycle of about 11 years. Solar eruptions can accelerate charged particles that cross roughly 93 million miles from the sun to Earth in about 30 minutes or less. Solar storms and fast solar wind can cause a geomagnetic storm, a disturbance in Earth's magnetic field. Auroras happen when charged particles collide with the upper atmosphere of Earth.

The sun has a hot outer atmosphere. The corona, the outer part of the sun's atmosphere, is much hotter than the sun's surface, and scientists are still studying why the corona is hotter than the layers just below it. The photosphere, the sun's visible surface, is roughly 4,500 to 6,000 degrees Celsius. Never look directly at the sun without special eye protection made for looking at the sun. Nothing could live on the sun, but its energy is vital for most life on Earth.

Words to know

• nebula: gas and dust
• diameter: width across
• rotates: spins around
• sunspots: cooler dark spots