Galactic plane

Even in the case of a barred spiral galaxy like the Milky Way, defining the galactic plane is slightly imprecise and arbitrary since the stars are not perfectly coplanar.

In 1959, the IAU defined the position of the Milky Way's north galactic pole as exactly RA = 12h 49m , Dec = 27° 24′ in the then-used B1950 epoch;[citation needed] in the currently-used J2000 epoch, after precession is taken into account, its position is RA 12h 51m 26.282s, Dec 27° 07′ 42.01″.

[citation needed] This position is in Coma Berenices, near the bright star Arcturus; likewise, the south galactic pole lies in the constellation Sculptor.

The zero of longitude of galactic coordinates was also defined in 1959 to be at position angle 123° from the north celestial pole.

The Galactic Center is located at position angle 31.72° (B1950) or 31.40° (J2000) east of north.