The Universe

• Big Bang Theory


  Theory that justifies the origin of the universe. It consists on the condensation of all the matter in the universe in a small area and the expansion of this matter about 13800 million years ago.
• Lightyear


  Unit that measures the distance light travels in one year. Used to measure distances between stars, galaxies, etc.
• Astronomical unit


  Unit used to measure distances inside the Solar System, as lightyears are too big for that measure.
• Galaxy


  Huge accumulation of nebulae and stars.
• Nebula


  Big cloud of gas and dust.
• Star


  Sphere of plasm (hot gas).
• Black hole


  Celestial bodies that absorb everything, even light. They are commonly found in the centre of galaxies.
• Planet


  Spherical body that orbits around a star.
• Satellite


  Celestial body that orbits around planets.
• Asteroid


  Irregular body that orbits around the Sun.
• Tide


  Periodical increases or decreases of the sea level, caused by the gravitational attraction of the Moon and the Sun on the water.
• Astrobiology


  Science that studies the origin, evolution and distribution of life in the universe.
• Types of matter in the universe

  • Ordinary matter (5%)
  • Dark matter (27%)
  • Dark energy (68%)
• Solar System


  Part of the Interstellar Neighborhood, Milky Way Galaxy
• The Sun


  Yellow dwarf star (hydrogen and helium)
• Planets


  • 4 rocky inner planets (Mercury, Venus, Earth, Mars)
  • 4 outer bigger planets (Jupiter, Saturn, Uranus, Neptune)
• Satellites


  Celestial bodies that orbit around a planet. They can be artificial or natural.
• Asteroids


  Irregular bodies that orbit around the Sun (Main Asteroid Belt, Kuiper Belt and Oort Cloud)
• Comets


  Irregular bodies that have a huge orbit around the Sun
• Dwarf planets


  Spherical bodies that orbit around the Sun but have irregular orbits
• Mercury


  • Closest to the Sun and smallest. Thin atmosphere, huge craters and big day-night differences in temperature. Slow rotation.
• Venus


  • Hottest. Very slow rotation. Many volcanoes.
• Mars


  • Red, huge sandstorms, 2 moons, covered in ice and likely underground liquid water -> microscopic life?
• Jupiter


  • Biggest planet. Fast rotation, 79 moons, big storms
• Saturn


  • 2nd biggest planet. Fast rotation, 53 moons, powerful winds, Rings
• Uranus


  • Coldest, sideways fast rotation, 27 moons, Rings
• Neptune


  • Farthest, fast rotation, 14 moons, Some rings
• Tides


  Caused by the gravitational attraction from the Moon and the Sun on the water