The Summer Triangle Star is an asterism composed of three stars: Vega (4 letters), ALTAIR (6 letters), and DENEB (5 letters). Vega is the brightest star in the constellation Lyra, ALTAIR is the brightest star in the constellation Aquila, and DENEB is the brightest star in the constellation Cygnus. Together, these three stars form a large triangle in the night sky, visible during the summer months in the Northern Hemisphere.