Introduction to Yindaoxian
Some galaxies are irregular and cannot clearly define the disk, even if Galaxy same spiral galaxy , also because stars Without complete coplanarity, it is difficult to clearly define the galactic plane. In 1959, IAU use 1950 points Of Epoch The precise location of the northern silver pole of the Milky Way is RA=12h49m, Dec=27 ° 24 '; use J2000 Epoch, revised again precession of the equinoxes Later, its position is RA 12h51m26.282s, Dec 27 ° 07 ′ 42.01 ″. This position is in Backseat , near bright fixed star Arcturus ； alike, Nanyinji stay Sculptor 。 In 1959, it was also defined that the position angle of "Silver Latitude 0" of the galactic coordinate is 123 ° from the North Celestial Pole, so the position of the galactic equator and Silver Latitude 0 is 17h42m26.603s, − 28 ° 55 ′ 00.445 ″ (B1950) or 17h45m37.224s, − 28 ° 56 ′ 10.23 ″ (J2000), and the position angle at J2000 is 122.932 °. The position angle of the center of the Milky Way is 31.72 ° north by east (B1950) or 31.40 ° (J2000).
