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

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

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..

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 the earth, or toward any other physical body heat.