Commonly used definitions include: Continued star-formation where the current SFR would exhaust the available gas reservoir in much less than the age of the Universe (the Hubble Time).
Definicións comunmente usadas son: Continuada formación de estrelas na que a actual SFR esgotaría as reservas de gas dispoñibles en moito menos tempo que a idade do Universo (o tempo de Hubble).