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Type 1a supernovae can be used as standard candles - AQA - A-Level Physics - Question 3 - 2020 - Paper 4
Question 3
Type 1a supernovae can be used as standard candles. 1. State what is meant by a standard candle. 2. Sketch on Figure 2 the light curve for a type 1a supernova. A... show full transcript
Worked Solution & Example Answer:Type 1a supernovae can be used as standard candles - AQA - A-Level Physics - Question 3 - 2020 - Paper 4
Step 1
Step 2
Sketch on Figure 2 the light curve for a type 1a supernova. Annotate your graph with suitable scales and a unit for time.
Answer
The light curve of a type 1a supernova typically shows a bright peak followed by a gradual decline. It peaks between -18 and -20 in absolute magnitude. The time scale usually ranges from approximately 40 to 500 days.
- The x-axis (time) should be labeled from 0 to 500 days.
- The y-axis (absolute magnitude) should be labeled with suitable scales, likely ranging from -20 to -18.
- Ensure that the graph line is steep in the early stages and then starts to decline after reaching its peak.
- The time unit for the x-axis should be in days.
Step 3
Describe how these values of distance are used, with other data, to find the Hubble constant.
Answer
To find the Hubble constant, the known distances of type 1a supernovae are compared with their recessional velocities derived from redshift measurements.
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Data Required:
- Distance measurements of type 1a supernovae (obtained using the standard candle method)
- Redshift (z) values, indicating the velocity of the supernovae.
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How Data is Used:
- The distance is plotted against the redshift on a graph to create a relationship between distance and velocity.
- The slope of the resulting line represents the Hubble constant (H₀), which describes the rate of expansion of the universe.
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Limitations:
- The accuracy of the distance measurements relies on the assumption that all type 1a supernovae have the same intrinsic brightness. Variations can lead to errors in distance calculations and therefore in determining H₀.
- Redshift values can also be affected by local gravitational fields, which may introduce further discrepancies.