Is the bulge of our Galaxy triaxial?

AS in the case of other spiral galaxies, such as M31 (refs 1, 2), the rotation curve of gas in our Galaxy indicates that its nuclear bulge is triaxial3. Despite several studies4,5 of the distribution of specific objects in the galactic bulge, no observational evidence of asymmetry has emerged. Recently, however, Blitz and Spergel6 have reanalysed balloon-infrared observations at 2.4 μm, where obscuration is relatively low, to suggest that the galactic bulge is bar-like, and tilted with respect to the plane of the Galaxy. Here we report that the distribution of IRAS (the Infrared Astronomy Satellite) bulge stars shows an asymmetry with respect to the Galactic Centre, providing clear evidence for triaxiality. © 1991 Nature Publishing Group.