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Discover the vital role of the Sun in our solar system, from its formation to energy production through nuclear fusion. Learn about key processes like convection and radiation, as well as intriguing features such as sunspots and solar flares. Explore how the solar system was born from a spinning nebula and the fascinating journey of planet formation. Dive into the captivating world of the Sun and its influence on life on Earth.
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Exploring the Sun: Our Local Star Don’t forget your sunblock! (2.2)
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? • 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
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 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 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 • 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 • 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 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 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
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 • 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 • 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
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: Magnetic fields explosively eject intense streams (solar wind) of charged particles into space
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