AST201H5 Lecture 3: AST201 Lecture 3 .docx
Document Summary
Units of angles: an angle is a number with units, degree: 360 degrees=full circle around the sky, too large for most objects moon =0. 5 degrees, smaller unit: 1 minute of arc (1 degree) =1 degree/60 still larger than most objects mars is smaller than 9,) 0. 3 degrees, smallest unit: 1 second of arc ( ")=1"/60, a common angular size mars <18"", refer to picture in textbook. Angles: the angle we see depend on two properties of the object, the actual size (in km) of the object, the distance (in km) to the object, what we see depend on the size of the actual object and the distance between us and the object, short distance makes an object have a smaller angle, angle depends on actual size (km)/distance (km, even if we do not know the size or the distance we still see the angle.
