Stars and planets

• What is the central star of our solar system called?

  The Sun
• How many planets are in our solar system?

  Eight planets
• What are the four inner planets of the solar system?

  Mercury, Venus, Earth, Mars
• What are the four outer planets of the solar system?

  Jupiter, Saturn, Uranus, Neptune
• What is the asteroid belt?

  A region with thousands of huge rocks
• What keeps the planets in orbit around the Sun?

  Gravity
• What is the order of the planets from the Sun?

  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
• What shape do the planets' orbits take?

  Slightly squashed circular (elliptical)
• What is a dwarf planet?

  A planetoid too small to be a planet
• What is an eccentric orbit?

  An orbit that is highly elliptical
• What are natural satellites called?

  Moons
• Which two planets have no moons?

  Mercury and Venus
• What are the main features of the solar system?

  • Eight planets
  • Dwarf planets
  • Moons
  • Comets
  • Asteroids
  • Asteroid belt
  • Central star (the Sun)
• What is the difference between a planet and a dwarf planet?

  • Planets: Large objects in orbit around a star
  • Dwarf planets: Too small to be considered planets
• What role does gravity play in the solar system?

  • Keeps planets in orbit around the Sun
  • Keeps moons in orbit around their planets
• How many planets are in the solar system?

  Eight
• What does the solar system consist of?

  A collection of planets orbiting the Sun
• What is the Sun part of?

  The Universe
• What are comets primarily made of?

  Rock and ice
• What happens to a comet as it approaches the Sun?

  The ice melts, producing a tail
• What type of orbit do comets have?

  Elliptical orbit
• Where are asteroids mainly found?

  In a belt between Mars and Jupiter
• What is a dwarf planet found in the asteroid belt?

  Ceres
• What may the rocks in the asteroid belt be remnants of?

  A planet that failed to form
• What is the risk associated with some asteroids?

  They may cross Earth's orbit
• How do comets and asteroids differ in composition?

  Comets are icy, asteroids are rocky
• What is the significance of Jupiter's gravitational attraction in the asteroid belt?

  It prevents the formation of a planet
• What is the family of planets that orbit around the Sun called?

  Solar system
• What forms the solar system?

  The Earth and seven other planets
• How many planets are in the solar system?

  Eight
• What is the relationship between the solar system and the universe?

  The solar system is part of the universe
• What are the inner four planets of the solar system?

  Mercury, Venus, Earth, Mars
• What type of planets are Mercury, Venus, Earth, and Mars?

  Rocky planets with solid surfaces
• Why do rocky planets form closer to the Sun?

  Dense materials are attracted strongly by gravity
• What are the outer four planets of the solar system called?

  Gas giants
• How did the gas giants form in the solar system?

  Gaseous substances gathered further from the Sun
• What happens to a dense hydrogen-rich cloud of gas and dust under gravity?

  It contracts and increases in temperature
• What is a protostar?

  The initial stage of a star's life
• What begins when nuclear fusion starts in a protostar?

  A star is born
• What forms the planets in a solar system?

  Swirling dust clouds around the star