Sunfire!

A former space explorer returns to his grandfather's empty house, trying to outrun what he witnessed on the distant planet Sunside. Kellard encountered something impossible there, something the alien intelligence called itself 'the children of the stars,' and it shattered everything he understood about human significance in the vast cosmos. Now a representative from the Survey appears, demanding answers about what destroyed his crew and what he glimpsed in those final transcendent moments. The revelation that humanity is insignificant in an ancient cosmic drama could break a man. Written in the 1960s, this is science fiction that takes seriously the psychological weight of contact with the unknowable, the strange grief of returning home after you've seen too much. It asks what remains of human purpose when the universe reveals its stranger truths.