Investigate how the spectra of stars can provide information
- Surface temperature can be obtained by observing the dominant wavelengths of a star’s spectrum and comparing this to a black body.
- The type and intensity of absorption spectrum can also indicate surface temperature.
- Translational velocity can be determined by the Doppler effect, i.e. red and blue shifts.
- Red shift indicates travelling away, while blue shift indicates travelling towards observer (BTRA – Buy Two Red Apples).
- Rotational velocity can be determined by both red and blue shifts of the opposite sides of a rotating body, which results in the broadening of spectral lines.
- Density can be inferred from pressure.
- Pressure is determined by examining width of spectral lines.
- Low pressures – sharp.
- High pressures – broad.
- Chemical composition can be determined by comparing absorption spectrum with known absorption and emission spectrum of elements, ions, and molecules on Earth.
Extract from Physics Stage 6 Syllabus © 2017 NSW Education Standards Authority (NESA)