Brown dwarf
For many years, efforts to discover brown dwarves were fruitless. In 1988, however, GD 165B was discovered, showing none of the features expected of a low-mass red dwarf star. Today, GD 165B is recognized as the prototype of a class of objects now called "L dwarfs". Although the discovery of the coolest dwarf was highly significant at the time, it was debated whether GD 165B would be classified as a brown dwarf or simply a very-low-mass star, because observationally it is very difficult to distinguish between the two.