Where is the center of the Milky Way?
Astronomers answered this question by carefully mapping the distribution of stars, and by 1930 they placed the center in the constellation Sagittarius, near its border with Scorpio. Looking in this direction with an optical telescope—all that was then available—revealed nothing of the center, which is totally obscured in the visible spectrum by broad lanes of dust, as shown in the photo. The size of these dust particles is approximately the same as the wavelength of visible light; therefore, this light is strongly scattered. Telescopes using light with a larger wavelength were clearly needed, and they were not long in coming.
