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Sun

The Sun’s Rotation

Sections of the Sun

The Core

The Radioactive Zone

The Convection Zone

The Photosphere

The Chromosphere

The Corona

 

 

Sun gif

 

As illustrated the sun rotates in an anti-clockwise direction as observed from its most northern point. The solid core rotates in much the same way as all the solid planets in the solar system, however as the outer shell is made up from gas and plasma, it spins at different speeds from the equator as it does in the poles (yet still in the same direction). At the equator the sun rotates faster, taking 26.8 Earth days to make a full rotation, whereas it takes up to 36 Earth days to make one rotation at the poles.

 

 

 

 

The Sun’s Rotation

The rotation of the suns outer layers have a very powerful effect on the magnetic field produced by the sun. Because the material of the sun rotates at different speeds it causes the magnet lines of force to become tangled and even tear. Magnetic lines of force can be viewed on a normal magnet using iron fillings. By placing a piece of paper above a magnet and sprinkling iron filings on the paper, curved lines appear between the north and south poles. The two ends of torn lines can show up on the Photosphere as sunspots where they cool the plasma considerably. Another effect of this can be solar flares that are massive expulsion of energy when the lines snap and reconnect and occasionally this forces an eruption of actual plasma from the Corona, a phenomenon we call Coronal Mass Ejection (CME).  Image credit NASA

 

 Sections of the Sun

 

Anatomy of the Sun (NASA) adapted.png

 

The Core

 The Sun’s core is its power source and where the heat and light which reaches us is created. The density at the core is 150 g/cm³ and approximately 15,000,000 °C (15,000,273 °K or 27,000,000 °F) which is more than enough energy required to sustain thermonuclear fusion. The core makes up about 25% of the Suns total radius (173,875 km / 108,050 miles) and towards the outer edge of the core the amount of nuclear reactions reduce significantly. As the nuclear reactions stop the temperature drops to about 7,500,000 °C (7,500,273°K or 13,500,000 °F) and so too does the density (approx. 20 g/cm³). Energy produced in the form of gamma rays and neutrinos are released into the next zone, known as ‘the radioactive zone’.

 

 

The Radioactive Zone

 

The radioactive zone is about 45% of the total radius of the sun and is 194,490 miles or 312,975 km thick. Within this zone energy produced in the core is transported towards the outer layers of the sun through photons. While travelling through this zone the photons come into contact with billions of particles and are reflected off into other particles. Photons are a packet of light and so travel at colossal speeds (299,792,458 metres per second) but even it takes the photons more than 170,000 years to pass through the radioactive layer. The density and temperature drops again by the outer point of the radioactive layer becoming about 2,000,000 °C (2,000,273°K or 3,600,032°F) and 0.2g/cm³.

 

 

The Convection Zone

 

This layer is about 129,660 miles or 208,650 km thick and stretches from the end of the radioactive zone right out to the edge of the Sun. By this point the temperature has decreased to below 2,000,000 °C and lager atoms are able to form such as carbon, nitrogen, oxygen, calcium, and iron. These atoms are in the form of plasma that boils and bubbles its way towards the outer layer. The heat trapped in the bubbles is hotter than the surrounding plasma and so it rises rapidly to escape which is where the convection zone gets its name. When the bubble bursts and releases the energy the material cools and falls back to the bottom of the zone. By the outer edge of the convection zone the temperature has dropped to 5,500°C (5,773°K or 9,932°F) and a density of 0.0000002g/cm³.

 

 

The Photosphere

 

This is the surface layer of the sun and is 500 km or 300 miles thick and this is the final layer that the energy passes through before being released. From this point the energy takes about eight minutes to reach us on earth in the form of heat and light. The temperature of the Photosphere is 5,426°C (5,700°K or 9,800°F) and a density of 0.0000002g/cm³. Strong magnetic fields on the Photosphere cause cooling of the material which can be seen in the form of sunspots (black spots). The Photosphere is surrounded by another layer called the Chromosphere but due to the intense light emitted by the Photosphere it overpowers the relatively dim light of the Chromosphere. 

 

 

The Chromosphere

 

This layer produces a red halo around the Sun due to the high amounts of hydrogen, which can be observed during an eclipse. When the moon blocks the sun a red ring is visible, this is the Chromosphere which is normally invisible by the light of the Photosphere. The temperature of this layer increases dramatically for reasons not fully understood but it is believed that it is due to a magnetic layer that coats the corona.

 

 

The Corona

 

This is the visible crown of the Sun; the temperature in this layer has now increased to about 2,000,000°C (2,000,273°K or 3,500,000°F).Massive waves of ejected matter explode out of this zone called Corona Mass Ejections (CME). The outer area of the Corona looses heat rapidly in the form of solar winds. These ‘solar winds’ are waves of radiation which are expelled into space and can cause many problems. Normally the magnetic field of the earth protects us from these waves but extremely powerful waves have been known to penetrate our natural defences.

 

 

Solar storm2.PNG

Illustration of a solar storm shedding vast amounts of radiation towards Earth which is protected moderately by its magnetosphere (a magnetic barrier created by the huge iron core and the Earth’s rotation).  Image credit NASA

 

 Quick Stats

Equatorial Radius

695,500 km or 432,200 miles

Density

1.409 g/cm3

Mass

1.989 x 1030 kg

Age

4,600,000,000 years

Spectral star type

G

Composition

92.1% hydrogen, 7.8% helium

and 0.1% other elements