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Space^15

At the centre of the Solar System is the Sun, a vast

globe of glowing gas that pours energy into space as

light and heat. From Earth, it looks the same size as the

Moon, which covers it during a. SOLAR ECLIPSE.

WHAT IS THE SURFACE OF THE SUN LIKE?

The surface of the Sun heaves and boils as pockets of hot gas well up and

sink back down. This gives the surface a grainy look, which is known as

granulation. Violent explosions called solar flares rip through the surface,

and giant fountain-like eruptions called prominences shoot superhot

gas far into space. Darker areas called sunspots often appear. They

are about 1,500°C (2,700°F) cooler than the gas around them.

A solar eclipse happens when the Moon passes

between the Earth and the Sun. It is a partial

eclipse if the Moon only covers part of the

Sun, and a total eclipse if the Sun is covered

completely. Two to five solar eclipses can be

seen from somewhere on Earth each year.

WHAT HAPPENS DURING A TOTAL SOLAR ECLIPSE?

When the Sun is completely covered, day suddenly turns

into night, the air chills, and birds start to roost. Totality (the

period of darkness) can last up to 7½ minutes, but is usually

much shorter. During totality, the pink inner atmosphere of

the Sun, the chromosphere, shows up. The pearly white outer

atmosphere, the corona, is also visible, and prominences can

sometimes be seen around the Moon’s dark edge.

WHAT IS THE SUN MADE OF?

The Sun is made up mainly of hydrogen (about 73 per cent) and helium (about

25 per cent). There are also traces of around 60 other elements (about 2 per cent).

Hydrogen is the fuel in the nuclear reactions that produce the Sun’s energy.

Diameter (distance across) 1.4 million km (865,000 miles)

Average distance from Earth 150 million km (93 million miles)

Time to spin around own axis 25.4 days (at Equator)

Mass 330,000 x Earth’s mass

Density 1.4 x density of water

Average surface temperature 5,500°C (9,900°F)

Core temperature 15 million°C (27 million°F)

Age 4,600 million years

1 MAGNETIC LOOPS
Magnetized loops of gas at a
million°C (1.8 million°F) arch for
thousands of kilometres above
the Sun’s visible surface.

INSIDE THE SUN 3

Nuclear reactions produce

the Sun’s energy in the central

core, where temperatures reach

15 million°C (27 million°F).

The energy is carried to the

surface first by radiation,

then by convection.

1 ECLIPSE SEQUENCE

The whole of a total solar eclipse takes about two hours. Light fades

dramatically in the last few minutes before the Moon covers the Sun.

During totality, when the Sun is completely covered, its faint outer

atmosphere shows up as a white haze around the Moon’s disc.

FIND OUT MORE. Heat 168–169 • Moon 17 • Nuclear Energy 167 • Stars 24–

SOLAR ECLIPSES

SUN

Sun

Prominence, a huge

fountain of hot gas

leaping thousands of

kilometres above

the Sun’s surface

Radiative zone, where

energy from the core

travels outwards

by radiation

Core, where massive

nuclear reactions

create enormous

amounts of energy

Convective zone, where

rising currents of hot gas

carry energy to the surface

SUN DATA

Solar flare,

a violent

explosion on

the surface

Sun

uncovered more

and more as

Moon moves on

Moon

covers up more

and more of Sun Totality

Sun