Exploring the Sun: Our Local Star
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Transcript of Exploring the Sun: Our Local Star
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Exploring the Sun: Our Local Star
Don’t forget your sunblock!(2.2)
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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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Where Did it Come From?• Current theory: Solar Nebula Theory
– Stars and planets formed together• A Star is a celestial body of hot gasses (H
and He)• When a star forms, its hot core remains
surrounded by gas and dust that hasn’t been pulled into the center– Gas and dust = nebula– Sometimes, this leftover material drifts into
space– Sometimes, it remains in the nebula, bound by
gravity
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How the Solar System Formed
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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
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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)
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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
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How the Solar System Formed
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How the Solar System Formed
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How the Solar System Formed
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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
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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
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Sun’s Nuclear Fusion
H
H
HeSmall atoms
Large atom
+ Energy!
• 1 g of Hydrogen provides enough energy for a home in Canada for about 40 years
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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 is balances with force of gravity pulling in matter toward core = stable star
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Sun’s Nuclear Fusion
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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
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Sun’s Nuclear Fusion
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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
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2 Important processes: Convection and Radiation
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Features of the Sun
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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
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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
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Solar Flare
Solar flare: Magnetic fields explosively eject intense streams (solar wind) of charged particles into space
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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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