AST 115 1st Edition Lecture 2Outline of Last Lecture I. Powers of Ten Notationa. The Astronomical UnitII. The Metric Systema. What do we mean by the size of an object?b. Metric Conversionsc. The Fundamental Unit of MassIII. Intro to Discovering the Night Skya. Illusions in the night skyb. The Naming of StarsOutline of Current Lecture I. Illusions in the night sky continuedII. Constellations of the ZodiacIII. Coordinate/Angle systema. Equatorial CoordinatesIV. Daily Paths of objects in the skyCurrent Lecture Illusions in the night sky o 2nd illusion: the Celestial Sphere (CS) Seems to be at the center of vast dome/sphere with black or grey interior Not real, but is used by astronomers to locate objects in the sky Imaginary grid to establish directions and bearings in the night sky:- Celestial Equator (CE): imaginary line on the CS directly above the Earth’s equator that divides the sky into northern and southern hemispheres.- North Celestial Pole (NCP): imaginary point just above Earth’s North Pole.- South Celestial Pole (SCP): imaginary point directly above Earth’s South Pole.o 3rd illusion: The Celestial Sphere appears to rotate around the Earth (going west) once in 24 hours. Causes the Sun, Moon, planets, and stars to appear to rise in East and set in the West.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Cause of this illusion: Earth’s rotation towards the East.o 4th illusion: the annual apparent eastward motion of the Sun along the inside of the CS. Cause of this illusion: Earth revolves around the Sun. The Sun’s annual path on the CS is called the Ecliptic.- This is also the name of the plane of the Earth’s orbit around the Sun The annual motion of the Earth also causes the stars to rise about 4 minutes earlier each night. This is the annual “Parade of Constellations”. (There are certain constellations that can only be seen during certain seasons). The Sun appears to move through “Constellations of the Zodiac” along the ecliptic. Zodiac = band of 12 – 13 constellations centered on the ecliptic o The Sun spends about 1 month at each constellation o The bright planets can always be seen within the boundaries of the Zodiac Why is this?- The orbits of the planets are nearly in the same plane of the ecliptic. Astronomers use a coordinate or angle system to locate faint objects in the skyo Equatorial Coordinates Declination (similar to latitude on Earth) Right Ascension (similar to longitude on Earth) Daily Pathso These paths depend upon your latitude on Earth At the North Pole, all objects in the sky move in paths parallel to the horizon. (Altitude of NCP = 90˚) At the Equator, all objects rise and set perpendicular to the horizon. (Altitude of NCP =
View Full Document
Unlocking...