Lecture Notes: Understanding the Universe

Satellites

• Definition: Objects that orbit a planet.
• Types:
  • Natural Satellites: Not man-made, e.g., the Moon.
  • Artificial Satellites: Man-made, e.g., communication satellites, orbiting telescopes.

Solar System

• Planets: Earth is one of eight planets orbiting the Sun.
  • Order (not necessary to memorize): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
  • Orbits: Slightly elliptical, not perfect circles.

Asteroids and Comets

• Asteroids:
  • Composition: Mostly rock and metal.
  • Location: Mainly in the asteroid belt between Mars and Jupiter.
• Comets:
  • Composition: Mostly ice and dust.
  • Orbits: More elliptical, often traveling to the outskirts of the solar system.

Galaxies

• The Milky Way Galaxy:
  • Contains billions of stars, each potentially having their own solar systems.
  • Our solar system is a small part located on one of the spiral arms.
  • Gravity holds stars together, and they orbit the galactic center.

The Universe

• Structure:
  • Composed of vast empty space, scattered with galaxies.
  • Galaxies are collections of billions of stars with their own solar systems.
  • Scale: The universe is immensely large, with great distances between galaxies.

Recap

• The universe consists of galaxies, which are massive groups of stars and solar systems.
• Solar systems have a central star orbited by planets, which may have satellites like the Moon.

• Conclusion: The lecture provided an overview of the hierarchy from satellites to the universe, emphasizing the vast scale and structure of space.