kepler motion planetary law second laws johannes orbits planet sun which keplers britannica definition elliptical time around areas move vector
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kepler physics laws law motion planetary second gravitation boundless shaded keplers third satellites ucm orbit time planet sun figure simplicity
radial velocity exoplanets radiale kecepatan doppler exoplanet shift shifts detecting astronomers metode wobble exoplaneten astronomy planets spectroscopy eridani observing starlight
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semu gerak ecliptic bumi celestial matahari astronomical poles map positions terhadap rotasi constellations britannica revolusi tahunan gerakan sumbu
time sidereal motions astronomy telling sun scale size click full local celestial
apparent coordinates latitude zenit observer movements determination geographic celestial declination horizontal