Solar system; stability of orbital motions; satellites

• What larger structure is the solar system part of?

  The Milky Way galaxy
• Why is the diagram of the solar system being shown, not to scale?

  Sizes and distances are extremely different
• What celestial body is located at the center of the solar system?

  The Sun
• What type of celestial object is the Sun?

  A star
• How many main planets orbit the Sun in our solar system?

  Eight
• Which planets are described as relatively small and rocky?

  Mercury, Venus, Earth, and Mars
• Which planets are described as much larger?

  Jupiter, Saturn, Uranus, and Neptune
• What lies beyond the orbit of Neptune?

  A number of dwarf planets
• Which dwarf planet is mentioned in the video?

  Pluto
• What is a characteristic of dwarf planets according to the video?

  They are extremely small
• Besides planets, what other objects are found in the solar system?

  Moons, asteroids, and comets
• What does the video say you need to be able to describe about moons?

  Moons are natural satellites orbiting planets
• What do moons orbit?

  Planets
• What is a common characteristic of most planets in the solar system regarding moons?

  They have at least one moon
• What is a galaxy defined as in the video?

  A massive group of stars
• How does the video describe the solar system's place in the Milky Way galaxy?

  A tiny part
• Approximately how many galaxies are there in the universe?

  Hundreds of billions
• How many stars does the Milky Way contain?

  Hundreds of billions
• From what do stars form?

  Clouds of dust and gas
• What do scientists call a cloud of dust and gas?

  A nebula
• What is the main element found in a nebula's gas?

  Hydrogen
• What is the first stage of star formation?

  Gravity causes collapse of the cloud
• What happens to the temperature as the dust particles move faster?

  The temperature rises
• What is the collapsing cloud of hot gas and dust called?

  A protostar
• What happens when the protostar's temperature gets high enough?

  Hydrogen nuclei form helium
• What is the process of hydrogen nuclei joining to form helium called?

  Nuclear fusion
• What happens at the point when the protostar turns into a star?

  Nuclear fusion starts
• What effect does nuclear fusion have on energy production in a star?

  Releases a huge amount of energy
• What force acts inwards on a star, tending to make it collapse?

  The force of gravity
• What effect does the energy from nuclear fusion have on a star?

  Tends to make the star expand
• What is the relationship between the force of gravity and the force due to fusion energy in a stable star?

  They are balanced
• What term do scientists use when the force of gravity is balanced by the force due to fusion energy?

  Equilibrium
• What do stars begin life as?

  A cloud of dust and gas
• What do scientists call a cloud of dust and gas?

  Nebula
• What effect does gravity have on a cloud of dust and gas?

  It causes the cloud to collapse
• What happens to the temperature of a collapsing cloud of dust and gas?

  The temperature rises
• What is the early stage of a star called?

  Protostar
• What happens when the temperature of a protostar gets high enough?

  Hydrogen nuclei join to form helium
• What type of star is formed at the point of nuclear fusion?

  Main sequence star
• What is the process of hydrogen nuclei joining to form helium nuclei called?

  Nuclear fusion