How do brown dwarfs differ from stars?

Brown dwarfs are astronomical objects that occupy a middle ground between planets and stars. While they share some formation characteristics with stars, they differ in several fundamental ways:

• Mass and Fusion: The primary distinction is that brown dwarfs do not reach the stable luminosities achieved by stars through the thermonuclear fusion of normal hydrogen. While stars have enough mass (typically above 0.08 solar masses) to sustain hydrogen fusion, brown dwarfs generally have a mass less than 0.075 that of the Sun.
• Internal Structure: Stars continue to contract and heat up until they can fuse hydrogen. In contrast, brown dwarfs prevent further contraction because their cores are supported by electron degeneracy pressure.
• Energy Production: Both stars and brown dwarfs may fuse deuterium during their early stages. However, once this process ends, brown dwarfs cool over time, whereas stars remain on the main sequence by fusing hydrogen for a significant portion of their lives.12