| Date | November 2016 | Marks available | 2 | Reference code | 16N.3.HL.TZ0.24 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 0 |
| Command term | Explain | Question number | 24 | Adapted from | N/A |
Question
Describe how some white dwarf stars become type Ia supernovae.
Hence, explain why a type Ia supernova is used as a standard candle.
Explain how the observation of type Ia supernovae led to the hypothesis that dark energy exists.
Markscheme
white dwarf must have companion «in binary system»
white dwarf gains material «from companion»
when dwarf reaches and exceeds the Chandrasekhar limit/1.4 MSUN supernova can occur
a standard candle represents a «stellar object» with a known luminosity
this supernova occurs at an certain/known/exact mass so luminosity/energy released is also known
OWTTE
MP1 for indication of known luminosity, MP2 for any relevant supportive argument.
distant supernovae were dimmer/further away than expected
hence universe is accelerating
dark energy «is a hypothesis to» explain this
