Chapter 6, Problem 12E

Look back at Figure 6.18 of Cygnus A and read its caption again. The material in the giant lobes at the edges of the image had to have been ejected from the center at least how many years ago?

Figure 6.18 Radio Image. This image has been constructed of radio observations at the Very Large Array of a galaxy called Cygnus A. Colors have been added to help the eye sort out regions of different radio intensities. Red regions are the most intense, blue the least. The visible galaxy would be a small dot in the center of the image. The radio image reveals jets of expelled material (more than 160,000 light-years long) on either side of the galaxy. (credit: NRAO/AUI)