DK Science: The Sun

Never look directly at the Sun, especially through a telescope or binoculars. Its glare may blind you.

Layers of gas surround the Sun, forming an atmosphere. The atmosphere’s outer layer is called the corona (crown). In ultraviolet light, it is revealed to be full of loops of hot gas. These coronal loops may rise as high and as wide as 500,000 km (300,000 miles). The inner layer of the Sun’s atmosphere is a pinkish colour and is called the chromosphere (colour-sphere).

From time to time, dark patches called sunspots appear on the Sun’s surface. These regions are around 1,500°C (2,700°F) cooler than the rest of the surface. They vary in size from a few thousand kilometres up to 100,000 km (62,000 miles). Sunspots may last for a few hours or several weeks. The number of sunspots rises and falls over a period of about 11 years – this is known as the sunspot cycle.

The surface of the Sun is a seething mass of gases, like a stormy sea. One of the reasons for this is its powerful magnetic field, which can be thousands of times stronger than Earth’s. Close up, the surface appears covered in speckles, called granulations, with dark sunspots and light areas caused by explosions called solar flares.

Scientists at the Sudbury Neutrino Observatory in Ontario, Canada, use a tank deep underground to detect particles called neutrinos. Neutrinos are produced at the centre of the Sun and other stars, and by studying them astronomers can learn more about the cores of stars. Neutrinos pass through matter, such as the Earth, and are detected underground because there is less interference from other particles.

The Sun constantly emits streams of electrically charged particles known as the solar wind. The solar wind is mainly responsible for the weather conditions in space around Earth. The Sun sometimes ejects a huge blast of particles, called a coronal mass ejection. This makes the solar wind stronger and can cause magnetic storms on Earth that affect compasses and disrupt radio signals.

Sometimes, as the Moon circles around the Earth, it passes directly in front of the Sun and blocks out its light. This is known as a solar eclipse. If the Moon only partly covers the Sun, we see a partial eclipse. If it covers the Sun completely, we see a total eclipse. A total eclipse is rare – usually the Moon passes slightly above or below the line between the Sun and the Earth. When a total eclipse occurs, day turns to night and the air becomes cold. A total eclipse can last for up to 7 1/2 minutes but is usually shorter.