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Pre-Main-Sequence Star

(PMS, PMS Object)
(star not yet with a nuclear reaction)

A Pre-Main-Sequence Star (PMS or PMS Object) is a star in an early stage after being a Protostar and before becoming a Main Sequence Star, in other words, before the star is burning Hydrogen in a nuclear reaction. At this early point, the star's energy is from gravitational contraction.

Some types:

Two distinctions used to classify pre-main-sequence stars and protostars are:

Active pre-main-sequence stars often emit X-rays and Ultraviolet rays.

(star type,stellar evolution,protostars)

Referenced by:
FU Orionis Star (FUor)
Gravitational Collapse
Hayashi Track
Stellar Evolution
T-Tauri Star (TTS)
Young Stellar Object (YSO)