A brown dwarf is a configuration or structure in space that is "incapable of sustained hydrogen fusion reactions." (Paul Murdin [editor-in-chief], 2001, Encyclopedia of Astronomy and Astrophysics, p. 784). These dwarfs cannot form a proton-proton chain because they are not hot enough, and do not naturally glow because they lack stable thermonuclear reactions. However, they are able to fuse helium with a "small amount of natural deuterium." But regardless, because brown drawfs do not follow the defined patterns of a star, they cannot be addressed as a "true star," but rather a "failed star." (James B. Kaler, 2001, Extreme Stars, p. 45).
The most evident approach to recognize a brown dwarf by its mass. This is because the brown dwarf contains a solar mass lower than 0.08. If there is "a faint body in orbit around a real star," one can learn the body's mass with the application of Kepler's laws. After this calculation, if the solar mass is lower than 0.08, then it is believed to be a brown dwarf. But because they are difficult to see, it is hard to use this method. More successful ways include a camera that can observe "in the infrared." And because the temperature of brown dwarfs are so cool, "they radiate most of their light in the infrared," causing the camera to detect a sign of a brown dwarf more easily. (James B. Kaler, 2001, Extreme Stars, p. 46). .
Brown dwarfs may be important because they are faint structures, that can explain part of the "dark matter" in the universe. Because these dwarfs emit little light and are difficult to see, if there are a huge number of brown dwarfs in space, it could be hypothesized that they make up most of the "dark matter." (James B. Kaler, 2001, Extreme Stars, p. 45).
Brown dwarfs are not important in relation to the dark matter problem because their masses are so low that there would have to be a great number of them in existence to even impact the dark matter problem.