Astrophysics

Question 1

Describe how a main star sequence is formed from a nebula (3 marks)

Answer 1

• Nebula is a cloud of dust / gas
• Gravity causes the cloud to collapse
• This causes the temperature to increase
• This creates a protostar
• A protostar becomes a main sequence star when fusion starts

Question 2

Describe the evolution of stars of similar mass to the sun, you should refer to temperature and brightness of the stars (6 marks)

Answer 2

• The nebula collapses and forms a protostar
• The temperature and brightness of the protostar increases
• When the temperature becomes hot enough fusion starts and the star becomes main sequence
• The brightness and temperature of the main sequence star depends on its mass
• When hydrogen runs out the main sequence becomes a red giant
• Red giants are brighter than main sequence but cooler than most main sequence stars
• Red giant becomes a white dwarf
• White dwarfs are less bright than red giant and main sequence stars
• White dwarfs are hotter than red giant and most main sequence stars

Question 3

Describe how a main sequence star becomes a white dwarf (4 marks)

Answer 3

• Fusion in the main sequence star stops in the core
• This causes the core to collapse
• This causes the core temperature of the star to increase
• The star becomes a red (super) giant
• The surface temperature of the star decreases
• Helium fusion begins
• White Dwarf formed when helium fusion stops

Question 4

Give two pieces of evidence for the Big Bang Theory (2 marks)

Answer 4

• Cosmic Microwave Background Radiation (CMBR)
• Red shift of galaxies

Question 5

Explain how CMBR and Red Shift of Galaxies are evidence to support the Big Bang Theory (4 marks)

Answer 5

• CMBR
  o CMBR comes from all directions, it is everywhere
  o This implies that all parts of the Universe were in contact a long time ago
  o CMBR wavelength has increased as the Universe has expanded
• Red Shift
  o The further the galaxy is from earth, the greater the red shift
  o The greater the red shift the faster the galaxy is moving away

Question 6

Describe the evidence that supports the Big Bang Theory (4 marks)

Answer 6

• Presence of Cosmic Microwave Background Radiation
• CMBR comes from all directions, it is everywhere
• This implies that all parts of the Universe were in contact a long time ago
• CMBR wavelength has increased as the Universe has expanded
• Red Shift of galaxies
• The further the galaxy is from earth, the greater the red shift
• The greater the red shift the faster the galaxy is moving away

Question 7

Describe the evolution of the Universe from the Big Bang to the present day (3 marks)

Answer 7

• The universe began as a hot dense point
• Universe has expanded since the Big Bang
• The Universe has cooled since the Big Bang