Estrelas

Stars

Stars are classified by its spectral type (temperature) and by its class of luminosity. The spectral type is classified by decreasing order of temperature as OBAFGKM(SRN). A good mnemonic is Oh, Be A Fine Girl (Guy) Kiss Me Sweetly Right Now. Each letter has subdivisions from 0 to 9 (O3-O9, B0-B9,A0-A9...). There is no star hotter than O3. The letter S correspond to stars with the same temperature as the stars M, but show ZrO absorption bands. Stars R and N are carbon stars with similar temperatures of G, K and M stars. About the luminosity classes, they are in decreasing order: Ia - Luminous Super Giants, Ib - Less luminous Super Giants, II - Luminous Giants, III - Giants, IV - Sub Giants and V - Main Sequence. All stars begin its lifes in the Main Sequence, burning H into He at its cores. At this phase, the more massive the star, the higher the nuclear reaction rates, hence, hotter and more luminous the star is. In high resolution spectra the line width may be related to some factors as the rotational speed. For instance, Altair show a very quick rotation with a period of 6,5h, revealing a large Ha line.

In order to understand how stars are classified from their spectra, read this text (in French, sorry).

In this page high resolution spectra are presented in white background, medium resolution in blue background and those of low resolution are presented in black background.

Stars are presented in alphabetic order.

Much of these spectra may be downloaded in format FIT from the Fachgruppe Spektroskopie database.