sub·​stel·​lar | \ ˌsəb-ˈste-lər How to pronounce substellar (audio) \
variants: or sub-stellar

Definition of substellar

of a celestial object
: having less mass than a star : not having the mass required to sustain nuclear fission Subsequent hunts within young stellar clusters have flushed out droves of brown dwarfs. Prime targets are the Pleiades cluster and star-forming regions in Orion and Taurus, where substellar bodies rival stars in number.— Robert Irion Very often, the most publicized events in astronomy involve the detection of fundamentally new types of objects. The discovery of a substellar object, a "brown dwarf" some dozens of times as massive as Jupiter, falls in this category.Physics Today

First Known Use of substellar

1949, in the meaning defined above

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The first known use of substellar was in 1949

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