What class of celestial bodies represents the quintessential "failed stars," sitting between the largest planets and the smallest true stars?
Answer
Brown dwarfs
Brown dwarfs are defined as objects that fall short of stellar ignition criteria, occupying the mass range above gas giants but below the minimum mass required for sustained hydrogen fusion.

Related Questions
What is the critical minimum mass generally cited for an object to achieve sustained hydrogen fusion and be classified as a true star?What class of celestial bodies represents the quintessential "failed stars," sitting between the largest planets and the smallest true stars?What is the primary, though brief, energy source for brown dwarfs that distinguishes them from gas giant planets?According to the provided mass spectrum table, what is the approximate upper mass limit, in Jupiter masses ($M_J$), for an object to be classified as a gas giant planet?Why is Jupiter often debated as a 'failed star' despite its immense size compared to other planets?Which major telescope was instrumental in observing dim, substellar objects falling on the boundary between large planets and low-mass brown dwarfs?What mass characteristic is generally required for massive stars to undergo the advanced fusion leading to a Type II supernova explosion?What distinguishes a 'failed star' like a brown dwarf from Jupiter, according to the text's distinction between object types?What state do brown dwarfs settle into after their brief deuterium-burning phase concludes?What is the primary factor dictating whether an object passes or fails the criteria for stellar life and death?