You've got objects that are giving off light, you've got telescopes that are collecting that light, and you've got instruments that are helping you understand what that light is.
빛을 발산하는 물체가 있고 그 빛을 모으는 망원경이 있으며 그 빛이 무엇인지 이해를 돕는  도구가 필요하지요.