Universe - All mass, energy, space and time., Galaxy - Collection of stars, dust remnants and gas held together by gravity., Solar System - Collection of celestial objects orbiting a star., Star - A luminous sphere of gas, that emits light and heat , held together by its own gravity., Planet - A celestial body that orbits a star, possesses enough mass to exist as in a circular shape and has cleared its orbital neighbourhood., Satellite - A celestial body that orbits a planet., Rotational Period - Time taken to complete one full rotation., Orbital Period - Time taken to complete one full orbit., Solstices - Time of year when one hemisphere experiences its longest day (summer solstice) whilst the opposite hemisphere experiences its shortest day (winter solstice)., Equinoxes - All locations on Earth experience equal length of night and day., Lunar Month - The time taken for the Moon to complete one full orbit of the Earth is equal to 27.3 days (aka sidereal cycle). However, due to the orbital motion of the Earth around the Sun it takes 29.5 days for a (synodic) lunar cycle., Lunar Phase - Stage in the (synodic) lunar cycle that describes the fraction of the moon that appears illuminated when view from Earth., Orbital Height - Distance from surface of planet to satellite., Orbital Radius - Distance from centre of planet to satellite, Geostationary Orbit - Orbit with a period of 24 hours. Satellites in tis orbit appear to be stationary when viewed from Earth as they stay above the same location on Earth due to the orbital period of the satellite being equal to the rotational period of the planet.,

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