The Big Dipper (US) or Plough (UK) is an asterism consisting of the seven brightest stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez (δ), of third magnitude. Four define a "bowl" or "body" and three define a "handle" or "head". It is recognized as a distinct grouping in many cultures. The North Star (Polaris), the current northern pole star and the tip of the handle of the Little Dipper, can be located by extending an imaginary line from Merak (β) through Dubhe (α). This makes it useful in celestial navigation.