SC 9.1

• Structure of the Sun

  • massive ball of gases
  • Composition of Sun
  • Hydrogen (76%)
  • Helium (22%)
  • Other element (2%)
  • Only star in Solar system
  • classified as a G-class dwarf star
  • Matter at the centre of the Sun is denser compared to Earth's rock or steel
  • Although the density is high, matter in the Sun still exists in a gaseous state due to the extremely high temperature, that increases the movement of atoms, and ionise them to form plasmatic matter
• Characteristic of the Sun

  • 25.04 Earth's day per rotation on its axis
  • 330420 * Earth's mass
  • density : 1.41 g/cm^3
  • 27.9 times Earth's gravity
  • 109 times diameter of Earth
  • 149680000km from Earth
  • 6000 degree celsius on the surface
  • 15 million degree celsius in the core
  • 8 minute taken for its light to reach Earth
  • 1.37 kW per meter square of energy reaches Earth in one second
• Corona layer

  • Thin layer of gases above the chromosphere
  • The Sun's outermost layer
  • Extends 5 millions of kilometers into outer space
  • Extremely low gas density
  • The temperature is about 1.5 million ° C and forms a bluish-white circle that appears during a full solar eclipse

  
• Chromosphere layer

  • Thin layer of gases on top of the photosphere
  • The temperature is about 6000-20000 ° C with a thickness of about 10,000 km
  • The chromosphere appears as a bright red circle around the Moon during a full solar eclipse
  • The bright red color is produced by hydrogen gas at high temperatures
  • very low-density gases
• Photosphere layer

  • The surface layer of the Sun can be seen with the help of a telescope
  • Consists of layer of high-density gases
  • The temperature is about 6,000 ° C and the thickness is about 400 km
  • The sunlight that can be seen from the Earth comes from the photosphere
  • Convection occurs due to explosions that occur on the surface of the Sun (Turbulent seen)
  • yellow light
• Convection zone

  • The Sun's layer above the radiation zone and below the photosphere
  • Consists of plasma
  • a type of gas that can conduct electric current
  • The convection zone extends from a depth of 200,000 km to the photosphere
  • Electromagnetic radiation from the radiation zone moves to the convection zone producing an outward vortex (rotating plasma) and transfer of heat more rapidly than transfer of heat through radiation
  • The flow of energy moves in a vortex forming convective cells as in a boiling kettle
  • Range of temperature : 5500 - 500000 degree celsius
• Radiation zone

  • Energy from the Sun's core travels outward through the radiation zone in the form of electromagnetic radiation (photons)
  • Heat transfer through radiation from atom to atom
  • Takes 100000 year to transfer heat from core to convection zone
  • The radiation zone extends 70% of the Sun's core, which is approximately at a depth of 200,000 - 515.00 km below the Sun's surface
  • Range of temperature : 1.5 million - 15 million
  • Lower temperature compared to the core due to random spread of the energy from one atom to another in all direction
  • Thickness : 300000 km
• The thickness of the radiation zone varies between stars and some have no radiation zone
• Core

  • The deepest layer at the center of the Sun
  • The temperature is about 15 million ° C
  • Extreme high temperature ionizes the atoms and form plasma
  • Allows thermonuclear fusion to take place
  • generate / release of heat and light energy
  • 99% of heat energy ,and sunlight come from the combination of two hydrogen-2 nuclei that form one helium-3 nucleus and one neutron
  • The source of the Sun's energy
• Granule

  • Lump of gases (Grainy structure) that formed on the surface of the sun due to high temperature difference between core layer and photosphere layer
  • Only occurs for a few minutes
  • The presence of granule makes the surface of the photosphere uneven
  • Temperature : 5800 degree celsius
  • Average diameter : 1000 km
• Sunspots

  • Dark regions seen on the surface of the Sun
  • Appear dark due to lower temperature than the surrounding areas (Granules)
  • Locations of very large eruptions in the photosphere
  • Last more than a week
  • Phenomena that always exist in pairs of group
  • Activity of sunspots seems to appear and disappear according to a 11 year cycle - Solar cycle
• Prominence

  • A huge loop or arched column of glowing gases over the sunspot
  • Can reach heights of hundreds of thousands of kilometres and may last for several days or months
  • Very strong and can throw out matter from the Sun into the space at speeds ranging from 600 km/s to more than 1000 km/s
  • Can be seen near the edge of the sun during an eclipse of the Sun
  • Emit charged particles (plasma, hydrogen and helium gases) and ultraviolet rays into outer space
• Solar flare

  • Column of large amount of charged gases erupting from the Sun and often occurs near sunspots
  • Strong and spectacular explosions of gases
  • Extreme explosion can cause coronal mass ejection
  • Attain maximum brightness level within a few minutes or hours
  • Spout charged gas particles at high speeds into outer space
  • Light from solar flare (Speed of light) takes 8 minutes to reach Earth
  • Charged gas particles take 10 minutes to reach Earth
  • Often collide with atoms and molecules in Earth's atmosphere to produce aurora in the air space around Earth's poles
• Coronal mass ejection

  • Huge cloud of plasma that erupts from the Sun and often occurs together with solar flare which are huge and strong
  • Ejection of magnetic gas particles
  • Spout magnetic particles at high speeds into outer space and appears like an expanding cloud
  • Takes three days to reach Earth
  • Also will produce aurora
• Solar Wind

  • High energy particles in plasma such as electrons, protons and alpha particles that erupt from the Sun to outer space travel together at high speed
  • Carries interplanetary magnetic field along with it
  • Speed of solar wind is supersonic with value ranging from 250 km/s to 750 km/s
  • The speed, temperature and density of the solar wind changes along the course of it's movement
  • Sunspot and solar flare activities increase the strength of the solar wind
• Earth's magnetosphere

  • Earth's magnetic field produces a protector known as magnetosphere
  • Earth's magnetosphere - a region in outer space surrounding Earth where the magnetic field's in Earth's magnetosphere is a combination of Earth's magnetic field (as the prime magnetic field) and the magnetic field in the region in outer space
  • Formed by the interaction between the magnetic field brought by the solar wind and Earth's magnetic field
  • As the number and energy of particles brought by the solar wind change, the shape of the magnetosphere also change.
• Importance of Earth's magnetosphere

  • Protect Earth from the adverse effects caused by dangerous particle from the Sun or other bodies in the Universe
  • Function as a biological shield to protect life on Earth from the adverse effects of solar wind
  • Block charged particles such as electrons, protons and alpha particles in the solar wind from reaching Earth. Excessive numbers of charged particles in Earth's atmosphere will disrupt telecommunication, navigation system and electric power lines
  • Reduce the pressure exerted by solar wind on Earth's atmosphere
• Aurora

  • Charged particles as as result of solar flares reach the North Pole or the South pole of the Earth and collide with gas molecule in the atmosphere
  • As a result, colourful light that consist of green, yellow and red light are produced
  • These light that can be seen at night are called aurora