The term 'Star in the Summer Triangle' refers to three stars that form a triangle in the night sky during the summer months. These stars are DENEB (5 letters), Vega (4 letters) and ALTAIR (6 letters). DENEB is the brightest star in the constellation Cygnus, Vega is the brightest star in the constellation Lyra, and ALTAIR is the brightest star in the constellation Aquila. Together, these three stars form the Summer Triangle, a prominent asterism in the night sky during the summer months.