Belzs

Belzs is a term used in astrophysics to denote a class of sub-Neptune exoplanets discovered with radii between 1.5 and 2.5 Earth radii and orbital periods less than 10 days. The designation originates from a 2018 survey of the Kepler field by the NASA Exoplanet Archive, where the acronym was coined to describe a subset of planets that appeared to host thick hydrogen‑helium atmospheres despite their close proximity to their host stars. Subsequent observations with the Hubble Space Telescope have identified a atmospheric water vapor signature in several Belzs objects, suggesting that they retain volatile‑rich envelopes. In planetary formation models, Belzs are considered transitional bodies between rocky super‑Earths and gas giants, providing insight into atmospheric loss processes. Researchers also use the term in climate modeling of exoplanetary weather patterns. The term has not entered common usage beyond scientific literature and remains a niche classification within exoplanet research.