Science
What is the Sun?
Quick answer
The Sun is a star at the centre of our solar system. It is a huge ball of hot gas that gives us light and heat, and it is about 150 million kilometres from Earth.
In one sentence
The Sun is the star at the middle of our solar system, and its light and heat make life on Earth possible.
Explained
The Sun looks small, but only because it is far away. It is about 150 million kilometres from Earth. Its light travels at 300,000 kilometres every second, and it still takes about 8 minutes and 20 seconds to reach us. The Sun is a ball of hot glowing gas, mostly hydrogen and helium. It is about 1.4 million kilometres wide, which is about 109 Earths side by side, and more than a million Earths could fit inside it.
sun
planet
star
Why does it shine? Deep in the Sun's core, hydrogen is squeezed so hard that it joins together to make helium. This is called nuclear fusion, and it releases huge amounts of energy as light and heat. The core is about 15 million degrees Celsius. The surface that we see is much cooler, around 5,500 degrees Celsius. Above it is the thin outer atmosphere, the corona, which you can see during a total solar eclipse. Dark patches called sunspots are slightly cooler areas on the surface.
The Sun holds about 99.8 percent of all the mass in the solar system. Its gravity keeps the planets in orbit; see the solar system. It is about 4.6 billion years old and has enough fuel to keep shining for about 5 billion years more.
Without the Sun there would be no life on Earth. It warms the planet, drives the winds and the water cycle, and gives plants the energy for photosynthesis. Solar panels turn sunlight into electricity.
Never look directly at the Sun, not even through sunglasses, binoculars or a telescope, because it can badly damage your eyes. Wear sun cream and a hat, too.
Examples
| Fact | Value |
|---|---|
| Distance from Earth | about 150 million km |
| Age | about 4.6 billion years |
| Surface temperature | about 5,500 °C |
| Core temperature | about 15 million °C |
| Light travel time to Earth | about 8 minutes 20 seconds |
Common mistakes
- "The Sun is on fire." It does not burn like a log. Nuclear fusion powers it.
- "The Sun is yellow." It is white; the atmosphere makes it look yellow.
- "The Sun is a planet." It is a star.
Quick quiz
The Sun
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What is the Sun?
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Related topics
The solar system
The solar system is the Sun and everything that orbits it, including eight planets, their moons, dwarf planets such as Pluto, asteroids and comets.
Light
Light is a form of energy that travels in straight lines, very fast. We see things when light from them enters our eyes, either because they make light or because they reflect it.
Seasons
Seasons happen because Earth is tilted. As Earth orbits the Sun over a year, each half of the planet takes turns leaning towards the Sun, getting more direct sunlight and longer days.
Stars
A star is a giant ball of hot, glowing gas that makes its own light. The Sun is our nearest star, and the others look like tiny points because they are so far away.
Day and night
We have day and night because Earth spins once around every 24 hours. The side facing the Sun has daylight, and the side facing away is in darkness.
Solar and lunar eclipses
An eclipse happens when the Sun, Earth and Moon line up. In a solar eclipse the Moon blocks the Sun; in a lunar eclipse Earth's shadow falls on the Moon.