8.1 Solar system, Orbit Motions & Satellites

• Where does the Sun lie in the Solar System?

  At the centre of the Solar System
• What percentage of the Solar System's mass does the Sun make up?

  Over 99%
• How many planets are there in the Solar System?

  8 planets
• What is the gravitational field around planets capable of?

  Pulling in nearby objects except satellites
• How does the gravitational field of a dwarf planet compare to that of a planet?

  It is not strong enough to pull in nearby objects
• Name the four rocky planets in the Solar System.

  Mercury, Venus, Earth, Mars
• Name the four gas planets in the Solar System.

  Jupiter, Saturn, Uranus, Neptune
• What distinguishes artificial satellites from natural satellites?

  Artificial satellites are man-made
• What is the International Space Station (ISS)?

  An artificial satellite orbiting Earth
• What do asteroids and comets do in the Solar System?

  They orbit the Sun
• What is an asteroid?

  A small rocky object orbiting the Sun
• Where is the asteroid belt located?

  Between Mars and Jupiter
• What are comets made of?

  Dust and ice
• How do comets behave as they approach the Sun?

  The ice melts and forms a tail
• What is our solar system a part of?

  The Milky Way galaxy
• How many stars are estimated to be in the Milky Way galaxy?

  Billions of stars
• What is the Universe composed of?

  Many different galaxies
• What is the mnemonic to remember the order of the 8 planets in the Solar System?

  • My Very Excellent Mother Just Served Us Noodles
  • Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
• What was Pluto's classification before 2006?

  A planet in the Solar System
• How many galaxies are estimated to be in the universe?

  More than 100 billion galaxies
• What happens to planets and moons in the Solar System?

  They reflect light from the Sun
• How far are the outer regions of the Solar System from the Sun?

  Around $5 \times 10^9 \text{ m}$
• How long does light take to reach Earth from the Sun?

  8 minutes
• How long does light take to reach the nearest star after the Sun?

  4 years
• What is the speed of light?

  $3 \times 10^8 \text{ m/s}$
• How can you calculate the time taken for light to travel a certain distance?

  $time =$$\frac{distance}{speed}$
• What is the radius of Mercury's orbit?

  $5.8 \times 10^9 \text{ m}$
• Calculate the time taken for light from the Sun to reach Mercury.

  19.3 seconds
• What happens when the temperature of a star increases?

  The star expands due to increased pressure
• What occurs if the temperature of a star drops?

  The star contracts due to decreased pressure
• What elements are formed by nuclear fusion in stars?

  All except hydrogen
• What happens when two hydrogen nuclei collide with enough energy?

  They fuse into a helium nucleus

  
• What is released during nuclear fusion?

  Energy in the form of heat and light
• What happens as a star runs out of hydrogen?

  Other fusion reactions form new elements
• What elements are formed in fusion reactions lighter than iron?

  Elements lighter than iron
• How are elements heavier than iron produced?

  In supernova explosions
• What occurs during a supernova?

  A star explodes and releases energy
• What are the stages in the life cycle of solar mass stars?

  1. Nebula
  2. Protostar
  3. Main Sequence Star
  4. Red Giant
  5. Planetary Nebula
  6. White Dwarf
  7. Black Dwarf

  
• What is a nebula?

  A giant cloud of hydrogen gas and dust
• What happens during the protostar stage?

  Gravity pulls particles into a hot ball