The peculiar variable star R Aquarii and its jet

Outward motion of the nebula associated with the symbiotic variable R Aquarii was suspected by Hubble¹ and confirmed by Baade², who estimated its ejection ~600 yr ago. A new feature of the nebulosity near the star appeared between 1970 and 1977 as found by Herbig from direct plates obtained with the 3-metre telescope at Lick Observatory. The `spike' or `jet' so-called by Wallerstein and Greenstein³ appears as a protrusion from the central star. The observational properties of the jet in both the optical and radio are described by Sopka et al.⁴. The near UV image obtained in 1980 by Herbig and the VLA radio map⁴ are shown combined in Fig. 1. Here we suggest that the jet is the result of supercritical accretion of mass transferred from the cool 387-day period Mira to the hot companion in a highly elliptical orbit. Ancient Japanese astronomical records suggest a nova outburst in AD 930 may be associated with R Aquarii which formed the outer extended nebulosity. The jet may help explain the outbursts of this object as well as the excitation of the R Aquarii nebula.