A Delta Scuti star is a classification of star.
Lieutenant Commander Una Chin-Riley made a firsthand observation of 99 Pegasi, a triple-mode high-amplitude Delta Scuti star when the USS Enterprise approached it within half a light year during her first deep space cruise aboard the ship.
She would later recall this to an envious Ensign Spock while they were stuck in a turbolift in 2254. (ST: "Q&A")