Spectroscopy & Classification
Splitting light into its spectrum to read the composition, temperature, motion, and magnetic fields of distant objects — and classifying stars by what their spectra reveal.
In brief
Reading the spectrum of light.
Techniques in this category
- PolarimetryTechniqueMeasures: The polarisation of light
Measuring the polarisation of light, which carries information no brightness or spectrum can — magnetic-field geometry, scattering by dust and grains, and the physics of everything from stellar surfaces to the cosmic microwave background.
- Spectral ClassificationTechniqueMeasures: A star's type from its spectrum
Sorting stars by the lines in their spectra into the sequence O, B, A, F, G, K, M — a classification that turned out to be an ordering by temperature, and the basis of the Hertzsprung–Russell diagram.
- SpectroscopyTechniqueMeasures: Composition, temperature, and motion
Spreading light into its spectrum to read the fingerprints of the elements. Spectral lines reveal what an object is made of, how hot it is, how it moves (through the Doppler shift), and the strength of its magnetic fields — the single most powerful tool in astronomy.
Knowledge connections
- Group includesSpectroscopy
- Group includesSpectral Classification
- Group includesPolarimetry
Sources
The primary and reference sources this topic draws on.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.