字幕表 動画を再生する 英語字幕をプリント How dark or light are asteroids. Join the 321Science team as we explore asteroid albedo. What does "albedo" mean? It's a word created from the latin word "albus", which means white. The root of the world albus is used in many common english words Scientists use it to describe the amount of light reflected back from a surface and give it a value between 0 and 1. How much light is reflected back from a surface? That depends on the surface material. Very dark surfaces such as new asphault on a road reflect little, and absorb more of the light, so they appear dark. Very light surfaces, such as sea ice or snow reflect a lot of light, so they appear bright. Scientists measure the albedo of different, well-known materials in labs. Astronomers measure the albedo of planets, moons, comets and asteroids through telescopes. They compare albedos and spectral observations of asteroids to learn about asteroid surfaces and composition Bennu's albedo is .04 to .05, which tells scientists that it is dark and probably carbon-rich. OSIRIS-REx's visit to Bennu will help scientists refine the measurements of its albedo and other characteristics. To learn more about Bennu, albedo and OSIRIS-REx, click on the links. This video is an OSIRIS-REx production. OSIRIS-REx is a partnership of the University of Arizona, NASA Goddard Space Flight Center and Lockheed Martin.