Messier 87 (NGC 4486) is a giant elliptical galaxy that harbours an active nucleus in its centre. The central black hole is fed by a small gas disk, and it powers a highly collimated, energetic jet that penetrates the inner part of the galaxy. As a typical elliptical galaxy, it primarily contains old, fairly cold stars - they cause the reddish colour of the galaxy in this colour image. The powerful jet, however, is extremely energetic and emits much of its energy in the blue and ultraviolet parts of the spectrum. The jet, therefore, appears bright blue in comparison