The system is based on the discovery of Joseph of Fraunhofer in the year 1813 that in the solar spectrum dark absorption lines are visible. Robert William Bunsen and Gustav RobertKirchhoff discovered 1859 then that these lines from the situation are identical with emission lines, which are delivered by certain chemical elements.
The conclusion lay near that these elements had to be present in the sun. The spectrographic analysis was justified. Apart from the analysis of materials upthe earth so also the stellar spectra could be analyzed.
The following seven basic classes and three subclasses exist:
|Class||characteristic||color||temperature in K||of example stars|
|O||ionized helium (He II)||blue||30000-50000||Mintaka (?), Naos (ζ Puppis)|
|B|| neutral helium (He I)|
Balmer series hydrogen
|blue-white||10000-28000||Latch plate, Spicahalio|
|A||hydrogen, calcium (approx. II)||knows||7500-9750||Wega, Sirius|
|F||calcium (approx. II), occurrence of metals||white-yellow||6000-7350||Prokyon, Canopus|
|G||calcium (approx. II), iron and other metals||yellow||5000-6900||Capella, sun|
|K||strong metal lines, late titanium oxides||orange||3500-4850||Arcturus, Aldebaran|
|M||Titanoxid||rotorange||2000–3350||Beteigeuze, Antares, Kapteyns Stern|
|R||Cyan (CN), Kohlenmonoxid (CO), Kohlenstoff||rotorange||3500–5400||S Camelopardalis, RU Virginis|
|S||Zirkonoxid||rotorange||2000–3500||T Camelopardalis, U Cassiopeiae|
|N||Kohlenstoff||rot||1900–3500||R Leporis, Y Canum Venaticorum, UHydrae|
common donkey bridge: “Oh, A fine girl, kiss ME right now.“
, The spectral classes O to A were in-patriated as early spectral classes to call the spectral classes F to G middle spectral classes and the remaining spectral classes as late spectral classes. ThoseDesignations early, means and come of to the acceptance overhauled in the meantime, the spectral class legend late somewhat over the level of development of a star out. Despite this erroneous organization are these designations this very day used, and a star is considered as sooner or later, if its spectral class compared withsome different one more near at the class O or because of the class M is.
In order to be able, become to classify the stars more exactly the spectra further in the individual classes from 0 to 9 gradated. There are itself today several systems of the spectral classification this way of writingthe spectral type serve and its classes this system adapt. In the original Harvard system and its extension, which MK-system, which defines additionally the Leuchtkraftklassen, not all this Subtypen also used. After B3-Sterne B5-Sterne, the class B4 follows is for example directly jumped over.
The spectral classes with theirsieved Grundtypen (O, B, A, F, G, K, M) constitute approximately 99% of all stars, why the other classes are often neglected. As noticing set for these spectral classes the sentence serves:
- “O A Fine Girl Kiss ME (right Smack Now) “: O B A FG K M (R S N)
- „obviously using astronomer terrible gladly amusing noticing sayings “: O B A F G K M.
- „Oh, with all fixed stars Gibt's characteristic characteristics “: O B A F G K M.
The following classes cannot be arranged in the sequence:
|W||of wolf Rayet stars|
in addition can be marked characteristics in the spectrum by additives:
|C||particularly sharp lines|
|D||Zwergstern (Hauptreihe; English. dwarf)|
|sd||Unterzwerg (English. sub dwarf)|
|n, nn||vague lines|
|e, em||emission lines|
|p, pec||characteristics with line intensity (English. peculiar, „particularly “)|
|m||strong metal lines|
|comp||compound (English. composite) spectrum|
|of v, var||variable spectrum|
partial becomes these additives by indication of the Leuchtkraftklasse, the 1943 of William Wilson Morgan and Philip Keenan were introduced (therefore it also: MK-system), redundantly. Pickering began the classification as well as Williamina Fleming in the year 1890, to compile Antonia Maury and Annie Jump Cannon. Pickering proceeded alphabetically and arranged the classes with capital letters from A to Z according to that Balmer series (transitions of the electron trajectories in the hydrogen spectrum).
Annie Jump Cannon stated very soon that the sequence was not meaningful. To the gradation the blue-white shining, hot Easter came to the red, relatively cools m and N-stars.
Furthermore it turned out that some the classes onlyon exposure errors been based or no sense had and therefore to be omitted could. The gradation was made dependent no more on the spectrum, but on the temperature of the stars.
First attempts to bring order into the brightness and temperature from stars to had 1865 the Italian Pater in the year Angelo Secchi with a three speed scale undertaken and 1874 Hermann Carl bird with a system, into which also those admitted up to then stellar evolution theories had flowed, what to constant changes led.
- of Carlo Jaschek, M. Jaschek: The classification OF of star, Cambridge: CambridgeUniversity press, 1987