The nature of our Milky Way Galaxy is reexamined from an eclectic point of view .
Evidence for a central bar , for example , is not reflected in the distribution of RR Lyrae variables in the central bulge [ 4,5 ] , and it is not clear if either a 2-armed or 4-armed spiral pattern is appropriate for the spiral arms .
Radial velocity mapping of the Galaxy using radio H I , H II , or CO observations is compromised by the assumptions adopted for simple Galactic rotation .
The Sun ’ s local standard of rest ( LSR ) velocity is \sim 14 km s ^ { -1 } rather than 20 km s ^ { -1 } , the local circular velocity is 251 \pm 9 km s ^ { -1 } rather than 220 km s ^ { -1 } , and young groups of stars exhibit a 10–20 km s ^ { -1 } “ kick ” relative to what is expected from Galactic rotation .
By implication , the same may be true for star-forming gas clouds affected by the Galaxy ’ s spiral density wave , raising concerns about their use for mapping spiral arms .
Proper motion data in conjunction with the newly-estimated velocity components for the Sun ’ s motion imply a distance to the Galactic centre of R _ { 0 } = 8.34 \pm 0.27 kpc , consistent with recent estimates which average 8.24 \pm 0.09 kpc .
A cosinusoidal Galactic potential is not ruled out by observations of open star clusters .
The planetary nebula cluster Bica 6 , for example , has a near-escape orbit for a Newtonian potential , but a near-normal orbit in a cosinusoidal potential field .
The nearby cluster Collinder 464 also displays unusually large tidal effects consistent with those expected for a cosinusoidal potential .
A standard Newtonian version of the Virial Theorem for star clusters yields very reasonable masses ( \sim 3 \times 10 ^ { 11 } M _ { \odot } and \sim 4 \times 10 ^ { 11 } M _ { \odot } ) for the Milky Way and M31 subgroups of the Local Group , respectively .
A cosinusoidal relation should yield identical results .