lowmass

Low mass is a relative descriptor used across science to indicate objects or components whose mass is small compared with a reference class or scale. Because what counts as “low” depends on the context, the term carries a qualitative meaning rather than a universal threshold.

In astronomy, low-mass refers primarily to stars and substellar objects. On the main sequence, low-mass stars are typically those with masses well below the high-mass end, such as red dwarfs with masses around 0.5 to 0.8 times that of the Sun. These stars burn hydrogen slowly and have very long lifetimes. Objects with masses below roughly 0.075 solar masses do not sustain stable hydrogen fusion and are categorized as brown dwarfs or other substellar bodies. Brown dwarfs occupy a transitional regime between planets and stars and cool as they age. Low-mass binary systems, including low-mass X-ray binaries, feature a compact object accreting material from a relatively light companion.

In planetary science, low-mass planets refer to terrestrial or Earth-sized bodies, in contrast to gas giants. Such planets are of particular interest for studies of composition, atmospheres, and potential habitability, though their detection is more challenging in many observational regimes.

In particle physics and cosmology, low-mass particles or structures denote those with masses far below the electroweak scale, including elementary particles like electrons and neutrinos, as well as small-scale cosmic structures in theoretical models. The concept is inherently contextual, contrasting with more massive or energetic constituents in a given framework.

Overall, low mass serves as a flexible shorthand for relative scale, guiding descriptions of composition, dynamics, and evolution across disciplines.