Imagine that the Sun went out. It is only a pretend question. The Sun will not suddenly disappear, and scientists have no reason to expect it. So here is what is true about the Sun, and why it matters so much to Earth.

As of November 2026, the Sun has been shining for billions of years. It will keep shining for about 5 billion more years. In about 5 billion years the Sun will swell into a red giant. The Sun is a star, the star at the center of our solar system.

You may have heard that the Sun is on fire, like a giant campfire. In fact, it is a giant, glowing ball of hot gas. Inside it, hydrogen is squeezed together into helium. This is nuclear fusion, and it makes the Sun's heat and light. The Sun's core is about 15 million degrees Celsius.

Light from the Sun takes about 8 minutes to reach Earth. So we always see the Sun as it was about 8 minutes ago. The Sun is about 93 million miles (150 million kilometers) from Earth, as of November 2026.

Space is so big that we measure it in light-years. A light-year is the distance light travels in one year. It is about 6 trillion miles (9.5 trillion kilometers). The nearest star to our Sun is Proxima Centauri, about 4.24 light-years away, as of November 2026.

The Sun is one star among 100 billion or more in our galaxy, the Milky Way. It is much bigger than any planet. It would take almost 1,000 Jupiters to fill it up.

The Sun gives Earth its light and its warmth. Its gravity pulls on Earth and the other planets. It keeps them circling around it. Earth is the third planet from the Sun.

Plants use the energy in sunlight to make their food. This is called photosynthesis. The Moon does not make its own light. It shines because sunlight reflects off its surface.

Sunlight reaches only the top of the ocean. Below about 1,000 meters the ocean is completely dark. Yet deep in the dark ocean, hot springs called hydrothermal vents have living things that do not depend on sunlight.

Words to know

• fusion: joining together
• galaxy: a star city
• Proxima: a near star
• hydrothermal: hot water
• photosynthesis: plants making food