The Sun Basics Cheat Sheet

1. Overview of the Sun

• Type: G-type main-sequence star (Yellow Dwarf)
• Distance from Earth: ~149.6 million km (1 AU)
• Diameter: 1.39 million km (109 times Earth’s)
• Mass: 1.989 × 10³⁰ kg (~333,000 times Earth’s)
• Surface Temperature: ~5,500°C (9,932°F)
• Core Temperature: ~15 million °C (27 million °F)
• Gravity: 274 m/s² (28 times Earth’s)
• Age: ~4.6 billion years
• Rotation Period:
  • Equator: ~25 Earth days
  • Poles: ~35 Earth days (Differential rotation)

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2. Structure of the Sun

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3. The Sun’s Composition

• Hydrogen (H): 74%
• Helium (He): 24%
• Trace Elements: Oxygen, carbon, neon, and iron.

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4. Energy Production

• Nuclear Fusion:
  • Hydrogen atoms fuse to form helium in the core.
  • Energy released as light and heat.
• Equation:

  4 Hydrogen nuclei → 1 Helium nucleus + Energy
  

• Energy Travel Time:
  • From the core to the surface: ~100,000 to 1 million years
  • From the surface to Earth: ~8 minutes (speed of light)

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5. Solar Phenomena

1. Sunspots:

• Cooler, dark patches on the photosphere caused by magnetic activity.
• Cycle: 11 years (Solar maximum/minimum).
• Temperature: ~4,000°C (7,232°F).

2. Solar Flares:

• Sudden energy releases from sunspots.
• Can disrupt Earth’s communications and cause auroras.

3. Coronal Mass Ejections (CME):

• Massive bursts of plasma and magnetic field from the corona.
• Can trigger geomagnetic storms on Earth.

4. Solar Wind:

• Continuous flow of charged particles (plasma) emitted by the corona.
• Shapes Earth’s magnetosphere and causes auroras.

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6. The Sun’s Magnetic Field

• Complex and Dynamic: Changes over an 11-year cycle (solar cycle).
• Polarity Reversal: Occurs every solar maximum (approx. every 11 years).
• Drives sunspots, flares, and CMEs.

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7. The Sun’s Influence on Earth

• Life and Climate:
  • Provides light and heat necessary for life.
  • Drives weather patterns and ocean currents.
• Tides and Seasons:
  • Influences Earth’s axial tilt, creating seasons.
• Geomagnetic Effects:
  • Solar storms can affect satellites, GPS, and power grids.

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8. Lifespan and Evolution of the Sun

• Current Stage: Main-sequence star (~4.6 billion years old).
• Remaining Lifespan: ~5 billion years.
• Future:
  • Red Giant (in 5 billion years): Sun expands, engulfing Mercury and Venus.
  • White Dwarf: After shedding outer layers, the Sun will shrink to a dense white dwarf.

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9. Interesting Facts

• Largest Object: Contains 99.8% of the solar system’s mass.
• Light Speed: Sunlight takes 8 minutes and 20 seconds to reach Earth.
• Volume: Can fit about 1.3 million Earths inside the Sun.
• Magnetic Field: Extends beyond Pluto, shaping the heliosphere.

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10. Solar Eclipses

• Total Solar Eclipse: Moon completely blocks the Sun.
• Partial Eclipse: Moon blocks part of the Sun.
• Annular Eclipse: Moon covers the Sun’s center, leaving a ring.

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11. Key Measurements

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12. The Sun in Mythology and Culture

• Named After: Latin “Sol” (root of solar).
• Mythology:
  • Greek: Helios (Sun god).
  • Roman: Sol Invictus.
  • Egyptian: Ra, god of the Sun.
• Cultural Significance: Central in festivals, rituals, and timekeeping across civilizations.

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13. Differences Between the Sun and Earth

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14. Can We Explore the Sun?

• Direct Exploration: Impossible due to extreme heat and radiation.
• Spacecraft Missions:
  • Parker Solar Probe (2018): Closest human-made object to the Sun (~7 million km).
  • Solar Orbiter (2020): Studies the Sun’s poles and solar wind.