ASTRON 89 1st Edition Lecture 1Outline of Last Lecture I. N/AOutline of Current Lecture I. Units of Measurement with respect to the sunII. Why is Pluto no longer a planet? III. A brief introduction to the Milky Way GalaxyCurrent LectureI. Units of measurement with respect to the Sun A. 1 Astronomical Unit (AU) = distance between the Earth and the Sun B. 1 Light year (ly) = distance light travels in 1 year a. Incorrect to say “x light years away.” Correct way is “x light years ago,” x being a value that represents a distance b. 1 ly = 9.46E12 km C. PARSEC = 3.26 ly II. Why is Pluto no longer a planet? a. Early 2000s, astronomers noticed new objects in our solar system i. The objects were moving, which indicates that they are relatively close to Earth (otherwise, we could not tell if they are moving or not) ii. They also noticed that these objects had an orbit1. The orbit was elliptical, but gravitationally bound to the suniii. Many more of these objects were found 1. These objects were called, “Trans Neptunian Objects” or “TNOs”b. The significance of these objects i. Caused scientists to rethink what the solar system is composed of. c. In 2006, International Astronomical Union passed a resolution that Pluto will no longer be a planet i. It was deemed a “dwarf planet”ii.III. A brief introduction to the Milky Way Galaxy d. Our solar system, consisting of 8 planets, resides in the Milky Way GalaxyThese 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.i. The dark regions between stars of a given universe that are often visible in photographs are depicting dust hiding in the stars 1. This dust reflects light from hot stars, which is why it is often perceived in color, such as blue.e. The Milky Way Galaxy is dynamic; it is always rotating i. The solar system is also dynamic; moving within the galaxyii. The shape of the galaxy is called barred spiral 1. Within the arms of the galaxy, new stars are being formed 2. The Milky Way is not the only galaxy that takes on this
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