Ad Astra - latin ; "to the stars"
One day Cas says, "Stars died for you, Dean Winchester", against ruffled hair perched atop sun kissed skin and sleepy eyes.
Dean stirs, moving to spread his palms against the contour of Cas’ back, tips of fingers languidly strumming the indentations of his spine. One, two, three, four, he counts, the closest he could get to scientifically studying the anatomy of the human body.
"Is this some physics crap again?" He frowns with eyes closed.
Cas smiles softly. "Far from it."
Dean’s fingers play at the base of his back, ninth thoracic vertebrae, Cas notes.
"Then tell me all about it."