orbit: The curved path of a celestial object or spacecraft around a star, planet, or moon, especially a periodic elliptical revolution..

axis: An imaginary line about which a body rotates.: "the earth revolves on its axis once every 24 hours".

galaxy: A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction..

gravity:The force that attracts a body toward the center of the earth, or toward any other physical body having mass. For most purposes Newton's laws of gravity apply, with minor modifications to take the general theory of relativity into account..

eclipse:An obscuring of the light from one celestial body by the passage of another between it and the observer or between it and its source of illumination.: "an eclipse of the sun".

1. nebulae:A cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter.