Finding Low-Mass Stars
Finding the low-mass stars that define the lower end of the main sequence is not easy
because they are
small and faint, emitting much of their light in the IR. Low-mass
main sequence stars are called red dwarfs. (Recall that another name for
a main sequence stars is "dwarf", but don't confuse red dwarfs with white dwarfs, which are not main sequence
stars.)
It is believed that small red dwarfs are
the most abundant stars in the Universe, but it is hard to confirm this because they are so faint.