Unit 8 Earth & Space Vocabulary Words Tools A B Revolution When the planets travels around the sun. Elliptical Orbits Ellipse shaped orbits whit two foci. Heliocentric Model that has the sun at its center. Geocentric Model tat has earth at its center. Zenith Point in the sky directly above the observer. satellites A smaller object revolving around a larger object. orbit The path and object takes around a star. perihelion Is the closest to the sun. aphelion the farthest away from the sun. Terrestial Planets made of solid rock. Jovian Planets made of gas. Rotation when a planet spins completely on its axis. Auroras Electrons from the sun's sunspots pulled into the earth atmosphere(northern lights) Comet Dirty Snowball. Meteor Meteorid entering the earths atmosphere. Asteroid large rock sizes of new jersey made up of metal cores orbiting the sun between the planets mars and jupiter. Retrograde motion When an planet apears to be moving west to east. Celestial sphere An inmaginary sphere serounding the earth. Celestial Object Any thing thats outside the celestial sphere.