THE SUN

Dominating our corner of space is a star we call the Sun. It travels through space with a family of planets, moons, and other bodies, which form the Solar System. The Sun is huge – over 100 times wider than Earth. It has the most mass of any object in the Solar System, 750 times more than all the other bodies put together. Sometimes the Moon passes in front of the Sun during the day and a SOLAR ECLIPSE occurs.

NSIDE THE SUN

Table 8. ESSENTIAL DATA

Diameter at equator 1,400,000 km (865,000 miles)
Distance from Earth149,000,000 km (93,000,000 miles)
Mass (Earth=1) 330,000
Average density 1.41 x water’s density
Rotation period 25.4 days (at equator)
Surface temperature 5,500°C (9,930°F)
Core temperature 15,000,000°C (27,000,000°F)
Age 4.6 billion years

WARNING!

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

LOOPS IN THE ATMOSPHERE

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).

SPOTS ON THE SUN

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.

STORMY SURFACE

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.

NEUTRINOS FROM THE SUN

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.

SPACE WEATHER

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.

SOLAR ECLIPSE

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.

SEEING THE CORONA

From Earth, observers cannot usually see the corona, or outer atmosphere of the Sun, because the photosphere (surface) is so bright. During a total eclipse, however, the moon blocks out the surface and we can see the Sun’s atmosphere. It appears as a milky halo around the Moon and extends millions of kilometres out into space. Its temperature can reach 3 million °C (5.4 million °F).

IN THE MOON’S SHADOW

During a solar eclipse the Moon casts a shadow on the Earth. Observers see a total eclipse if they are in the umbra, the central and darkest part of the shadow. Observers in the part-shadow, or penumbra, see a partial eclipse. As the Moon orbits the Earth, the umbra traces a path across the Earth’s surface known as the path of totality (total darkness), up to 270 km (170 miles) wide.

Copyright © 2007 Dorling Kindersley

stay connected

Sign up for our free email newsletters and receive the latest advice and information on all things parenting.

Enter your email address to sign up or manage your account.

Facebook icon Twitter icon Follow Us on Pinterest

editor’s picks

highlights

Top 10 Group Halloween Costumes for Families
These store-bought and Pinterest-inspired Halloween costume ideas for groups are the perfect way to show off your creative side at your Halloween party or while trick-or-treating.

Kindergarten Readiness App Wins Gold
Our Kindergarten Readiness app won the Gold Award of Excellence in the educational category at the 2014 Communicator Awards. This valuable checklist comes with games and activities to help your child practice the essential skills she needs for kindergarten. Download the Kindergarten Readiness app today!

12 Spine-Tingling Halloween Movies for Teens
Are you looking for a movie with just a little bit of spook-factor for your teen? Check out these 12 spine-tingling Halloween movies!

Find Today's Newest & Best Children's Books!
Looking for newly released books for your child? Try our new Book Finder tool to search for new books by age, type, and theme, and create reading lists for kids!