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The Sun is the star at the center of the Solar System. It is seen in the sky and gives

light to the Earth. When the Sun is in the sky, it is day. When the Sun is not in the

sky, it is night. The planets, including Earth, go around it.

The Sun gives off energy as electromagnetic radiation. That includes light, infra-red

energy (heat), ultraviolet light and radio waves. It also gives off a stream of

particles, which reaches Earth as "solar wind". The source of all this energy is thereaction in the star which turns hydrogen into helium and makes huge amounts of

energy.

The Sun is a star like many others in our Milky Way galaxy. It has existed for a little

over 4.5 billion years, and is going to continue for at least as long. The Sun is about

a hundred times as wide as the Earth. It has a mass of 1.98911030

kg, which is 333,000 times the mass of the Earth.[12]

Contents [hide]

1 In Astronomy

2 How the Sun was made

3 How the Sun works

4 Features of the Sun

5 Photosphere

6 Atmosphere of the Sun

7 Solar eclipses

8 The fate of the Sun

9 More reading

10 References

In Astronomy[change]

Our Sun makes up 99.86% of the matter in the solar system. Even the giant planet

Jupiter is tiny compared to the Sun. The planets in our solar system move aroundthe Sun in orbits. Our Sun can be seen in the sky in the day time. It is seen as a large

yellow ball. The Sun is basically a very, very large ball of plasma bubbling with

non-stop explosions. These explosions give off so much energy that if we could

gather all the Sun's energy for one second it would be enough to power the United

States for 9 million years. Even though the Sun is 93 million miles (150 million

kilometres) from the earth, we still feel this energy.

The Sun is so bright that it can hurt to look at it and can damage human eyesight,

so one should never stare at the Sun, and should never use binoculars or a

telescope to look at it. The Sun makes light, heat and the solar wind. Solar wind

moves past the Earth outside the Earth's atmosphere. It is made of plasma and

small particles that fly away from the Sun all the way as far as Neptune.

The solar wind is created by the bending, twisting, and breaking of the thousands

of magnetic fields in the Sun. There are so many of these magnetic fields because

the Sun's surface is constantly moving and creating many fields in more than one

spot.

The Sun is the main source of energy for life on Earth. It is no wonder that for

ancient peoples, the Sun was an object of sun worship.

The Sun is at the middle of our solar system. Each planet travels in an almost

round orbit around the Sun. Each planet orbits at a different distance from the Sun.

The orbits of the planets are not perfect circles. They are stretched circles called

ellipses. The planets closest to the Sun get more heat. Planets farther away arecolder. Only the Earth has a climate that is right for humans.

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Almost all life on Earth depends on the light energy that comes from our Sun.

Plants use solar energy as food so they can grow. This process is called

photosynthesis, the green in the plant leaves is a pigment which is called

chlorophyll.

In the center of the Sun, great heat and pressure combine hydrogen gas into

helium gas which produces very large amounts of energy. This is called nuclearfusion. Nuclear fusion is more powerful than chemical reactions such as fire.

The Sun seen in a telescope.

People can look at the Sun if they use special lenses that make it safe. When they

do this, darker spots are sometimes seen on the surface of the Sun. These spots are

called sunspots. The number of sunspots on the Sun gets bigger and then smaller

about every 11 years. These sunspots affect the weather on Earth and can also

affect electricity and electrical machines. Sunspots made a solar storm in 1989 that

shut down the electric power grid in Quebec and put the entire province in

darkness for nine hours.

How the Sun was made

Scientists think that the Sun started from a very large cloud of dust and small bits

of ice 4.6 billion years ago. At the center of that huge cloud, some of the material

started to build up into a ball called the Sun. Once this Sun got big enough, fusion

reactions inside it caused that ball make heat and for it to shine.

The light that was made from fusion in the Sun pushed away all the rest of the

cloud from itself, and the planets formed from the rest of this cloud.

How the Sun works

At its very center, hydrogen atoms collide together at great temperature and

pressure so that they fuse to form atoms of helium. This process is called nuclear

fusion. This fusion changes a very small part of the hydrogen atoms into a large

amount of energy. This energy then travels from the core to the surface of the Sun.

The Sun's surface is called the photosphere and is where it shines the energy into

space. Energy can take thousands of years to reach the Sun's surface because the

Sun is so huge and most of the way the energy is passed from atom to atom.

Features of the Sun

Since the Sun is all gas, surface features come and go. If the Sun is viewed through

a special solar telescope, dark areas called sunspots can be seen. These areas are

caused by the Sun's magnetic field. The sunspots only look dark because the rest of

the Sun is very bright.

Some space telescopes, including the ones that orbit the Sun have seen huge arches

of the Sun's matter extend suddenly from the Sun. These are called solar

prominences. Solar prominences come in many different shapes and sizes. Some of

them are so large that the Earth could fit inside of them, and a few are shaped like

hands. Solar flares also come and go.

Sunspots, prominences and flares become rare, and then numerous, and then rare

again, every 11 years.

Photosphere

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This is the surface of the Sun. The light that the Earth receives from the Sun is

radiated from this layer. Below this layer, the Sun is opaque, or not transparent to

light.

Atmosphere of the Sun[change]

Five layers make up the atmosphere of the Sun. The chromosphere, transitionregion, and corona are much hotter than the outer photosphere surface of the

Sun.[13] It is believed that Alfvn waves may pass through to heat the corona.[14]

The minimum temperature zone, the coolest layer of the Sun, is about 500 km

above the photosphere. It has a temperature of about 4,100 K.[13] This part of the

Sun is cool enough to allow simple molecules such as carbon monoxide and water

to form. those molecules can be seen on the Sun with special instruments called

spectroscopes.[15]

The chromosphere is the first layer of the Sun which can be seen, especially during

a solar eclipse when the moon is covering most of the Sun and blocking the

brightest light.

The solar transition region is the part of the Sun's atmosphere, between the

chromosphere and outer part called the corona.[16] It can be seen from space

using telescopes that can sense ultraviolet light. The transition is between two

very different layers. In the bottom part it touches the photosphere and gravity

shapes the features. At the top, the transition layer touches the corona.

The corona is the outer atmosphere of the Sun and is much bigger than the rest of

the Sun. The corona continuously expands into space forming the solar wind,

which fills all the Solar System.[17] The average temperature of the corona and

solar wind is about 1,000,0002,000,000 K. In the hottest regions it is 8,000,000

20,000,000 K.[18] We do not understand why the corona is so hot.[17][18]

The heliosphere is the thin outer atmosphere of the Sun, filled with the solar windplasma. It extends out past the orbit of Pluto to the heliopause, where it forms a

boundary where it collides with the interstellar medium.[19]

Solar eclipses

See Eclipse

The fate of the Sun

Astrophysicists say our Sun is a main-sequence star in the middle of its life. In

about another 4 to 5 billion years, they think it will get bigger and become a red

giant star. The Sun would be up to 250 times its current size, as big as 1.4 AU and

will swallow up the earth.

Earth's fate is still a bit of a mystery. Calculations suggest that Earth could escape

to a higher orbit. This due to the solar wind, which drops 30% of the Sun's mass,

but a newer study shows that Earth would possibly vanish due to the tidal

forces.[source?] This would happen while the Sun continues to get bigger.

However, the Sun will lose mass.

Anyway, Earth's ocean and air would have long since worn out. This is even though

the Sun is still in its main sequence stage. After the Sun reaches a point where it

can no longer get bigger, it will figuratively explode with passion, but not like a

supernova. Rather, it will expand rapidly and lose its layers, forming a planetary

nebula. Eventually, the Sun will shrink into a white dwarf. Then, over severalhundred billion or even a trillion years, the Sun would fade into a black dwarf.