Phases of the Moon and Percent of the Moon Illuminated Copyright Antonio Cidadao. Used by permission. Click on picture to see large version. From any location on the Earth, the Moon appears to be a circular disk which, at any specific time, is illuminated to some degree by direct sunlight. Like the Earth, the Moon is a sphere which is always half illuminated by the Sun, but as the Moon orbits the Earth we get to see more or less of the illuminated half. New Moon - The Moon's unilluminated side is facing the Earth. Waxing Crescent - The Moon appears to be partly but less than one-half illuminated by direct sunlight. First Quarter - One-half of the Moon appears to be illuminated by direct sunlight. Waxing Gibbous - The Moon appears to be more than one-half but not fully illuminated by direct sunlight. Full Moon - The Moon's illuminated side is facing the Earth. Waning Gibbous - The Moon appears to be more than one-half but not fully illuminated by direct sunlight. Lunation Movie Copyright Antonio Cidadao.
Retrograde Motion One phenomenon that aincient astronomers had difficulty explaining was the retrograde motion of the planets. Over the course of a single night, a planet will move from East to West across the sky, like any other celestial object near the ecliptic. (Most objects in our sky appear to rise somewhere on the Eastern horizon and set somewhere on the Western horizon. The only exceptions are stars near the North celestial pole, that stay above the horizon all the time and appear to make counterclockwise circles around the celestial pole. As one travels further North, the region of the sky that remains above the horizon at all times becomes larger, until the entire sky appears -to an observer at the North Pole- to be simply circling the North star. If observed from one night to the next, however, a planet appears to move from West to East against the background stars most of the time. Apparent Motion of Mars Against Background Stars Ptolemaic Explanation (This animated gif was obtained from Dr.
Planets - Zoom Astronomy Advertisement. EnchantedLearning.com is a user-supported site. As a bonus, site members have access to a banner-ad-free version of the site, with print-friendly pages.Click here to learn more. (Already a member? Click here.) The Planets (plus the Dwarf Planet Pluto) Our solar system consists of the sun, eight planets, moons, many dwarf planets (or plutoids), an asteroid belt, comets, meteors, and others. The eight planets that orbit the sun are (in order from the sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Easy ways to remember the order of the planets (plus Pluto) are the mnemonics: "My Very Excellent Mother Just Sent Us Nine Pizzas" and "My Very Easy Method Just Simplifies Us Naming Planets" The first letter of each of these words represents a planet - in the correct order. The largest planet is Jupiter. The inner planets are: Mercury, Venus, Earth, and Mars. Generally, the farther from the Sun, the cooler the planet. Density of the Planets The Mass of the Planets
The Last Shuttle