Astronomers study the light from distant stars to find out about their properties. Explain how the radiation received from a star can be used to determine its surface temperature and the elements present in its atmosphere.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Scientists can analyse the electromagnetic radiation emitted by stars without ever visiting them. The pattern of radiation across different wavelengths acts as a unique fingerprint for each star.
Model answer (5 marks)
Stars emit a continuous spectrum of electromagnetic radiation.
The peak wavelength (or colour) of this continuous spectrum is related to the star’s surface temperature by Wien’s displacement law.
When the star’s light passes through its atmosphere, atoms and ions absorb photons at specific wavelengths, creating dark absorption lines in the spectrum.
These absorption lines appear at characteristic wavelengths unique to each element.
By comparing the observed absorption lines with known laboratory spectra, astronomers can identify the elements present in the star’s atmosphere.
The peak wavelength (or colour) of this continuous spectrum is related to the star’s surface temperature by Wien’s displacement law.
When the star’s light passes through its atmosphere, atoms and ions absorb photons at specific wavelengths, creating dark absorption lines in the spectrum.
These absorption lines appear at characteristic wavelengths unique to each element.
By comparing the observed absorption lines with known laboratory spectra, astronomers can identify the elements present in the star’s atmosphere.
Examiner tips
- Use the phrase "continuous spectrum" and mention Wien’s law for temperature; mention absorption lines and element identification.
- Show the logical sequence: continuous spectrum → peak wavelength → temperature; absorption lines → element identification.
- Use UK spelling (e.g., "spectrum").
Common mistakes
- Confusing emission lines with absorption lines; not linking peak wavelength to temperature; failing to mention unique line patterns for element identification.
Mark scheme (5 marks)
- Stars emit a continuous spectrum of electromagnetic radiation / light
- The peak wavelength / colour of the continuous spectrum indicates the surface temperature of the star
- When light from the star passes through its atmosphere, certain wavelengths are absorbed by elements present
- This produces dark absorption lines / dark lines at specific wavelengths in the spectrum
- Each element has a unique / characteristic set of absorption lines, so the lines can be matched to known elements to identify what is present in the star's atmosphere
Key terms in this question
Related
- All Eduqas A-Level Physics revision notes →
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- Decode the mark scheme abbreviations →
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