Solar System

• What galaxy is our solar system apart of?

  The Milkyway
• How many planets make up our solar system?

  8 (plus dwarf planets)
• What do the planets orbit around? What type of body is it?


  The sun. The sun is a star.
• What type of force formed the sun?

  gravitational attraction force.
• What formed the sun?

  A cloud of dust and gas
• Describe what moons are?

  Natural satellites that orbit around planets.
• What word is used to describe a cloud of dust and gas?

  A nebula
• What is a galaxy?


  a large collection of stars
• How do stars form?

  Form from when clouds of dust and gas are drawn together by gravity. Gravity causes this cloud to collapse.
• what is the collapsing cloud called?


  A protostar.
• What happens when the temp of a protostar increases? What is this process called?

  Hydrogen nuclei join to form helium. Nuclear fusion
• What 2 opposing forces are acting on a star in nuclear fusion?

  What do they do?

  Gravity causes the star to collapse, which acts inwards.

  Fusion energy expands the star, acting outwards.
• How do the opposing forces create equilibrium in the fusion reaction.

  The 2 opposing forces balance one another out, which creates equilibrium.
• What is the star formed from this reaction called?

  Main sequence star.
• What is a star's life cycle determined by?

  The size of the star.
• How does a main sequence star go to a red giant?

  First, we have a main sequence star from nuclear fusion

  Hydrogen nuclei fuse to form larger nuclei, but the hydrogen starts to run out.

  The outward force due to fusion is less than the inward force of gravity

  The star collapses inwards and the temperature increases.

  Helium nuclei fuse to create heavier elements up to iron.

  The star expands to form a red giant.
• How does a red giant go to a white or black dwarf?

  The red giant would start to shrink and stop fusing helium which creates a white dwarf.

  This white dwarf gradually cools down and stops releasing energy and forms a black dwarf.
• What elements do nuclear fusion make up to?

  Elements heavy up to iron.
• how does a main sequence star become a super red giant?

  As the stars run of hydrogen, it leaves the main sequence stage.

  The star expands into a super red giant.

  Helium nuclei fuse to produce heavier elements.
• How does a super red giant form a supernova?

  The super red giant stops carrying out nuclear fusion.

  The star explodes which is a supernova.
• What happens when a supernova explodes?

  The temperature of a supernova increases and elements heavier than iron are produced and are distributed throughout the universe.
• What can happen after a supernova?

  A neutron star or black hole can be formed.
• Define a neutron star?

  A star with neutrons densely packed together.
• Describe a black hole?

  It has a large gravity in which light can't escape it.
• What is the term used to describe planets orbiting the sun?

  A circular orbit.
• What force maintains the circular orbit?

  Gravity.
• What example is a natural satellite?

  The moon.
• Give 2 example of artificial satellites


  TV satellites.

  Satellites used for satellite imaging.
• Explain how the force of gravity acting on a satellite affects its speed and velocity.

  It cannot cause a change of speed since there is no force component in the direction of motion.

  It can alter its velocity as the direction is always changing.
• Why does the radius of orbit change, if speed changes in order for a stable orbit?

  A higher speed requires a stronger force of gravity.

  Radius must decrease if speed increases.
• What is observed in distant galaxies? What is this called?

  There is an increase in wavelength of light and the galaxies are moving faster.

  The red shift.
• What does distant galaxies moving faster, provide evidence for?

  It shows that the universe is expanding and supports the big bang theory.
• What is the big bang theory?

  The idea that the universe began from a small region that was very hot and dense.
• What did scientists assume in 1998?

  Gravity would cause the expansion of the universe to gradually slow down.
• What observations disapproved this assumption?

  Observations of supernovae, which showed the rate of expansion is increasing.
• What have scientists suggested in recent years?

  The universe contains matter and energy that cannot be detected.
• What is this matter and energy called?

  Dark matter and dark energy.
• What 2 ideas could explain the increasing rate of the universe's expansion?

  The existence of dark matter and dark energy.

  Ideas are still being developed and are not fully understood.