Stellar Taxonomy

One of the advantages of taking a medium resolution spectrum is that it provided a clearer look at what the spectrum really represented.  Most of the stars on the survey were taken with a low resolution and this gave the opportunity to reclassify several stars based on the observations made at Kitt Peak.  The system of classification used was the MK system. The MK classification, or the Yerkes system, is an improvement from the Harvard system of spectral classification developed by Annie "Jump" Cannon.

The MK system relies heavily on the original Harvard system and can be characterized as an improvement.  It keeps the same spectral classes but changes some of the subgroupings.  The classical spectral classification is based on the acronym OBAFGKM, with O being hottest star and M being the coolest.  The age to which as star can live is related with its mass and position on the HR diagram.  O stars lead short and volatile lives, whilst any M star that has ever been formed since the beginnings of the universe is still in existence, with most still retaining their position on the main sequence. Here is a detailed explanation of the M-K system

                                                                        H-R Diagram                       Illustration Credit: D. Aaron Freed

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