Spectral Classification of Stars
- continuous spectrum of colours is produced by the hot, dense surface of a star such as the Sun.
- light from Sun, stars and others sources can be studied using an instrument called a spectrograph, attached to the viewing end of a telescope. (photo)
- spectrograph – it has a very small, slit-like aperture at the telescope’s point of focus so that only the light from a particular source enters the instrument.
- inside the spectrograph – a device called a collimator turns the cone of light into parallel rays and these are then split into a spectrum by a glass prism. (diagram)
- spectrum with more blue and than red point out as show a very hot star , such as a white dwarf, while a spectrum with more red than blue show out large – fairly col star such as a red giant.
- each of the chemical elements absorbs and emits the light at very accuracy wavelenghts and these produce spectral lines that can be used to identify the different elements present in a star.
- dark absorption lines – laying on continuous spectrum (continuum) shows that some of light has been absorbed on its way to Earth.
- for example – carbon absortion lines may show to point out that the light has passed through a cloud of interstellar dust. (See below – Emission Lines.)
On the right, this is called an emission line spectrum.
(Absorption lines and emission lines will be in the same place for the same gas.)
- clouds of high-temperature, low-pressure gas, such as nebulae to produce a spectrum that consists only a series of bright emissions lines. (diagram) (diagram)
- wide emission lines – rapidly rotating or expanding gas that may have been produced by a supernova.
Lists of Solar Observatories
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