I know there is GM discretion allowed as to the situations affecting a Solarian’s ability to enter a Stellar Mode, but I would like other GMs opinions on this situation.
RAW seem to generally require that the Solarian be "in combat" and facing a significant threat. In fact, the description specifically says that:
you must be facing a significant enemy (see page 242).
Description of Significant Enemy:
…a creature with a CR less than or equal to your character level – 4 is not a significant enemy
So… nowhere does it give consideration as to the Solarian’s personal situation.
In a hypothetical situation even a lowly CR-1 creature would present a dire threat to a Paralyzed 6th level Solarian, but she would not be permitted to enter Stellar Mode and become attuned, to use her Corona Revelation as a defense because of the low CR rating of the enemy.
In our example situation, the party encountered a group of Ghoul Soldiers who managed to paralyze the Solarian via bite. Combat moved into the next room, leaving the Solarian alone and still paralyzed (for 2 more rounds). I presumed the Solarian’s Stellar Mode ended because there was no current threat to her, and stated such. She argued that the state of paralyzation itself constituted a threat and/or the fact that I still had her in "melee round" mode meant she was still "in combat" (she wanted to become fully attuned so she could jump back in the fight if/when released from paralyzation). I ruled that it must be a threat from an enemy and that her Stellar Mode ended, but she was still in "melee mode" so I could track the rounds of her paralyzation; she was unhappy with this decision.