The third-largest constellation, lying in the northern sky and better known as the Great Bear. Its seven main stars make up the familiar shape known as the Plough or Big Dipper. Its two brightest stars are Dubhe (Alpha Ursae Majoris) and Alioth (Epsilon Ursae Majoris), both magnitude 1.8. Mizar (Zeta Ursae Majoris) is a famous naked-eye double. Xi Ursae Majoris is a binary of magnitudes 4.3 and 4.8 and a period of 60 years; it was the first binary to have its orbit computed. Lalande 21185 is the fourth-closest star to the Sun. M81 and M101 are spiral galaxies of 7th and 8th magnitudes. M82 is an 8th-magnitude peculiar galaxy, now thought to be a spiral seen edge-on that is undergoing a burst of star formation. M97 is the Owl Nebula.