Sun and Seasons

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drive wind bands – which drive surface currents

drive deep ocean currents

drive water cycle

drive weather

Credit: NASA GSFC Water and Energy Cycle

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Sun as a Source of Energy

Plants need light for photosynthesis

Without its heat, the only inhabitable areas on Earth would be near volcanic vents

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Young stars form in nebulae from Small Magellanic Cloud

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Star-forming region in the Large Magellanic Cloud:

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Our Sun is a Regular/ Small Star

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In a few Billion years… Red Giant

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Our Sun’s Habitable Zone

Billions of years ago, things may have been different

The Sun was cooler (by up to 30%!)

Earth’s atmosphere was different (thicker, carbon dioxide)

Conditions will be different in the future

By many accounts, increases in the Sun’s temperature will make Earth uninhabitable in 1 billion years or less

These changes will also affect other planets… Mars?

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By 5 billion years… White Dwarf

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Massive Stars are different

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Betelgeuse

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Supernova—Massive Star Explodes

Images at

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Done with the Sun

Time for Seasons!