• SNC 1D1 – The Sun

• The sun and other celestial objects in the Universe emit electromagnetic radiation as part of the electromagnetic spectrum (EM spectrum).

• The sun emits energy across most of the EM spectrum.• EM radiation from the sun drives the earth’s weather and

climate and provides energy for life.

The Structure of the Sun:• The sun is composed of many layers of gas.• The core of the sun has temperatures and pressures large

enough to fuse hydrogen atoms into helium atoms.• This reaction makes the core the hottest part of the sun with

temperatures in excess of 15 000 000 ˚ C. • The energy produced in the core passes to the radiative zone.• Over a very long period of time (up to 1 000 000 years) this

energy reaches the convective zone.• Energy continues to radiate out until reaching the

photosphere where light and other energy escapes.• The photosphere has a temperature of 5500˚ C • Above the photosphere is the sun’s atmosphere made up of

the inner chromosphere (60 000˚C) and the outer corona.

The Sun

The Sun’s Surface• The sun rotates on an axis and takes about 25 days for one

rotation.• As heated materials rise to the surface they cool and sink back

inside the sun.• These rising convection currents are called granules. • Sunspots are darker areas of the sun caused by disturbances

in the sun’s magnetic field.• Solar flares are found near sunspots and release large

quantities of gas and charged particles.• Solar prominences are slow low-energy ejections of gas that

travel through the corona.

The Sun’s Effect on the Earth• The gases in the sun cause solar storms.• These storms cause solar winds.• When solar winds pass through the earth’s magnetic field

they ionize gases in the earth’s atmosphere (oxygen, nitrogen, argon and carbon dioxide) producing a display of light.

• These lights are most pronounced near the poles where they are called the aurora borealis and the aurora australis

• Solar activity can also disrupt satellite signals, cell phone communications and satellite TV communication.

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