The Spiral Arms of the Milky Way Galaxy

[from the webpage] "The cardinal points of Galactic longitude are marked with dotted lines; these divide the Galaxy into four quadrants. Two angles of Galactic longitude indicate the preceding (50°) and following (285°) tangents of the Sagittarius-Carina arm, which brackets the concentrations of stars, gas and dust that limit our inward view of the Galaxy. Two other angles (60° and 240°) define a line approximately parallel to a rift or spur orbiting ahead of the Sun, variously referred to as the Local arm, the Orion arm, or the Cygnus-Orion arm.
Recent parallax measurements of several giant star forming regions put the Sun at about 8300 parsecs from the Galactic barycenter, in a relative void between the Perseus and Sagittarius-Carina arms. The Galaxy rotates in a clockwise direction; the Sun is orbiting in near tandem with the spiral arms at about 250 kilometers per second, 7.9 billion kilometers per year.