Space and the Solar System

Overview of the Galaxy

• Our galaxy is called the Milky Way.
• The bright light in the galaxy is our solar system.

The Solar System

• Composed of eight major planets revolving around the Sun.
• The Sun is the primary source of light for all planets.

Planets in Our Solar System

1. Mercury
   • Closest planet to the Sun.
   • A year on Mercury is 88 Earth days long.
   • Visible from Earth in 2016.
2. Venus
   • Second from the Sun and the hottest planet.
   • High carbon dioxide levels trap heat.
3. Earth
   • Unique with conditions suitable for life.
   • Has one natural satellite: Moon.
4. Mars
   • Known as the Red Planet.
   • Experiences large dust storms.
5. Jupiter
   • Largest planet.
   • Has four moons.
   • Shortest day: 9 hours 55 minutes.
6. Saturn
   • 150 frozen moons, largest is Titan.
   • Notable for its rings made of dust and ice.
7. Uranus
   • Very cold, with temperatures around -224°C.
   • Takes 84 Earth years to orbit the Sun.
8. Neptune
   • Takes 165 Earth years to orbit the Sun.
   • Known as the Ice Giant.
   • Has about 14 moons.

Dwarf Planets

• Five known: Ceres, Pluto, Eris, Makemake, and Haumea.
• Trivia: Jupiter's moon, Ganymede, has more water than Earth.

Formation of the Solar System

• Formed 4.6 billion years ago.
• Began with a cloud of dust and gas, influenced by a supernova.
• Formation led to a solar nebula.
• The Sun formed at the center, planets formed from clumps of matter.
• Hot center favored formation of Mercury, Venus, Earth, Mars, Jupiter.
• Cold edges favored Saturn, Neptune, Uranus.

Sun Specifics

• Takes 99% of solar system's mass.
• Layers: Corona, Chromosphere, Photosphere, Convective Zone, Radiative Zone, Core.
• Core temperature around 15 million °C.
• Comprised mainly of hydrogen and helium.
• The Sun will eventually become a red giant and then a black dwarf.

Moon Formation Theories

1. Capture Theory
2. Accretion Theory
3. Fission Scenario
4. Giant Impact Theory (most accepted)
   • Involving a collision with a Mars-sized body called Theia.

Earth's Formation

• Began 13.8 billion years ago with the Big Bang.
• Formed from an accretion disk of dust and gas.
• Surface initially hot and molten.
• Plate tectonics led to formation of continents.

Pluto's Planetary Status

• Declassified as a planet in 2006 by the International Astronomical Union (IAU).
• Criteria for being a planet:
  1. Orbit around the Sun.
  2. Spherical in shape.
  3. Clear neighborhood around its orbit (Pluto fails this).
• Now classified as a dwarf planet.
• Similar dwarf planets: Haumea, Makemake, Eris.