Tom Rauschenbach wrote:
I've noticed that stars are classified with letters of the alphabet.
This story
http://www.spaceref.com/news/viewpr.html?pid=18792
for example mentions "K stars" and "F stars". I'm wondering if this
system has a name. A Google search for "star categories" turned up
nothing useful.

I teach university classes about this topic every now and then.
You might look at some of my notes.

Introductory version:

http://spiff.rit.edu/classes/phys230...ec_interp.html

Intermediate version:

http://spiff.rit.edu/classes/phys301...ass/class.html

More advanced version:

http://spiff.rit.edu/classes/phys440...o_spectra.html
http://spiff.rit.edu/classes/phys440...pec_class.html

There are links to further information in these pages.

Michael Richmond