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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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