The Classification of L Dwarfs

To highlight the need for new spectral types, a brief review of the discovery of very low luminosity dwarfs — cooler than type M9.5 — is presented. The reasoning behind the choice of letters "L" and "T" is also given. Our philosophy of spectral classification is explained and we use this philosophy to construct an L dwarf typing scheme. The scheme, originally developed on only 25 spectra, has now been shown to work successfully on a sample of 92 L dwarfs.