Final answer:
The thickest part of the visible Milky Way is near the constellation Sagittarius. The bulge of the Milky Way, which is located in the central region of the galaxy, contains a large concentration of stars.
Step-by-step explanation:
The thickest part of the visible Milky Way is near the constellation Sagittarius. The Milky Way is a barred spiral galaxy, and Sagittarius is located in the central region of the galaxy, known as the bulge. This region contains a large concentration of stars, which makes it appear thicker compared to other parts of the Milky Way.