Classification of Stars
Stars radiate at all frequencies. Astronomers can deduce a star’s surface temperature from its colour as a star’s colour depends on its surface temperature. Different surface temperatures result in different colours. Their surface temperatures can be determined by accurately measuring its colour. Astronomers take multiple readings to find out the peak intensity wavelength.
The point of the wavelength of visible light closest to which the intensity is highest will be the dominant colour of the star and the star would appear to be that colour. In the example above, the point where the intensity is highest is at about a wavelength of 650nm, the colour of the star is red.
The stars of the constellations Scorpius as seen from Johor, Malaysia. Antares, the alpha star and also a super red giant is the bright orange star to the top right of the centre.
Stars are classified according to their colour on a scale based on temperature, reordering the alphabetical categories to fit as below.
The types of stars can be put into a mnemonic: Oh, Be a Fine Girl Kiss Me
Life Cycles of Stars | Diffuse Nebula | Main-Sequence Stars | Red Giants after Main-Sequence | Death of a Low Mass Star | Death of a High-Mass Star | Star Families | Magnitude Scale | Measuring Stellar Distances | Classification of stars | Wien's Law and Stefan-Boltzmannn Law for a Blackbody | Stellar Spectra