In astronomy, what is the next letter in the sequence O, B, A, F, G, K
K-type main-sequence star K-type main-sequence star A K-type main-sequence star (K V), also referred to as an K dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("red dwarfs") and yellow G-type main-sequence stars. They have masses between 0.5 and 0.8 times the mass of the Sun and surface temperatures between 3,900 and 5,200 K. Better known examples include Alpha Centauri B (K1 V) and Epsilon Indi. These stars are of particular interest in the search for extraterrestrial life because they are stable on the main sequence
Main sequence sequence O, B, A, F, G, K and M. (A popular mnemonic for memorizing this sequence of stellar classes is "Oh Be A Fine Girl/Guy, Kiss Me".) The luminosity class ranged from I to V, in order of decreasing luminosity. Stars of luminosity class V belonged to the main sequence. In April 2018, astronomers reported the detection of the most distant "ordinary" (i.e., main sequence) star, named Icarus (formally, MACS J1149 Lensed Star 1), at 9 billion light-years away from Earth. When a protostar is formed from the collapse of a giant molecular cloud of gas and dust in the