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Solar Nebula Theory and the Sun . Don’t forget your sunblock!. The Sun. Most important celestial object for life on Earth Contributes heat  moderate temperatures Contributes light  visibility Photosynthesis  provides autotrophs with energy to make food,  provides consumers with food.

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solar nebula theory and the sun

Solar Nebula Theory and the Sun

Don’t forget your sunblock!

the sun
The Sun
  • Most important celestial object for life on Earth
    • Contributes heat  moderate temperatures
    • Contributes light  visibility
    • Photosynthesis  provides autotrophs with energy to make food,  provides consumers with food
where did it come from
Where Did it Come From?
  • Current theory: Solar Nebula Theory
    • Stars and planets formed together
  • Star: Celestial body of hot gasses (H and He)
  • Star formation
    • A hot core surrounded by gas and dust
      • Gas and dust = nebula
    • Sometimes, this leftover material drifts into space
    • Sometimes, it remains in the nebula, bound by gravity
how the solar system formed1
How the Solar System Formed
  • Gravity sets gas and dust particles into motion
    • No resistance in space!
    • The closer the particles get to each other, the stronger the force of gravity
  • Particles aren’t perfectly aligned so they end up spinning around in a nebula
how the solar system formed2
How the Solar System Formed
  • Spinning nebula contracts and flattens into a disc
    • Accretion disc
  • Particles begin to gather in the centre of the nebula
    • Forming a protostar (hot, condensed object)
how the solar system formed3
How the Solar System Formed
  • Tiny grains or small lumps collect in nebula
    • Attract others and build up to bigger, rocky lumps called planetismals
  • If planetismals survive collisions, they may build up to full planets like those in our solar system
  • If their mass is >10x that of Jupiter, fusion begins and a star is formed
extrasolar planets
Extrasolar planets
  • Many planets have been discovered in orbit about stars other than the Sun
    • “extrasolar planets”
  • They can be detected by
    • A) the dimming of their star’s light as they pass in front of it
    • B) direct photos
how the sun formed
How the Sun Formed
  • Nebula collapses, contracts, and gas compresses
    • Friction of all that material in nebula causes a temperature increase
  • At 10 000 000°C, nuclear fusion begins
    • The combining of 2 atomic nuclei to form 1 large nucleus
    • H + H  He + energy
sun s nuclear fusion
Sun’s Nuclear Fusion

H

He

+ Energy!

Small atoms

H

Large atom

  • 1 g of Hydrogen provides enough energy for a home in Canada for about 40 years
sun s nuclear fusion1
Sun’s Nuclear Fusion
  • H nuclei combine to form Helium
    • Requires massive pressure and temp
    • Now called “protostar”
  • He is more dense that H
    • :. He settles in Sun’s core
  • Pressure in the core is very high. When it balances with force of gravity pulling in matter toward core = stable star
sun s nuclear fusion3
Sun’s Nuclear Fusion
  • When the sun converts ~ 10% of H to He, He core accumulates and undergoes fusion itself
    • Sun changes physically
      • He core grows
      • H fusion (ring around core) also grows
      • :. The sun is growing… yowsa!
      • ~ 30% larger than its protostar phase
structure of the sun
Structure of the Sun
  • He core (where solar energy is produced)
  • Radiative zone: 86% of sun’s energy radiates outward from core
  • Convective zone: outer layer transfers energy in convection currents back in towards sun
  • Photosphere: “surface” layer of sun
sunspots
Sunspots
  • Def: An area of strong

magnetic force on the photosphere

  • Sunspots are not dark, they are bright
    • Appear dark due to contrasting temperature to photosphere
      • Photosphere: 6000˚C
      • Sunspot: 4500˚C
sunspots1
Sunspots
  • By observing sunspots, astronomers learned the sun rotates in 27-35 days
  • Gradually grow, may fade and disappear altogether
  • Occur in 22-year cycles
solar flare
Solar Flare

Solar flare: Magnetic fields explosively eject intense streams (solar wind) of charged particles into space

solar flare1
Solar Flare
  • If one of the streams hits Earth, it can:
    • Disrupt telecommunication and electrical equipment
    • Usually beautiful auroras
      • Shimmery curtains of high energy, charged particles
      • Electric currents charging gasses in Earth’s atmosphere
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