What next for the likely presupernova HD 179821?

We have used the Owens Valley Radio Observatory Millimeter Array to obtain a map of the J =1 -->0 CO emission from the circumstellar shell around HD 1 79821, a highly evolved G-type star that will probably explode as a superno va in the next 10(5) yr. Very approximately, the gas presents as a circular ring with an inner diameter 3." 95 of an outer diameter of similar to 12 " , and azimuthal variations in the CO brightness of a factor of about 2. Unt il about 1600 years ago, the star was a red hypergiant, losing about 3 x 10 (-4) M-circle dot yr(-1) at an average outflow speed of 32 km s(-1). We pro pose that when HD 179821 explodes as a supernova, it may resemble Kepler's supernova remnant, and thus some of the anisotropies in supernova remnants may be intrinsic. If the factors that cause the anisotropic mass loss in HD 179821 persist until the moment when the star explodes as a supernova, the newly born pulsar may receive a momentum "kick," leading to a space motion of close to 700 km s(-1). Independent of the angular asymmetries, the radi ally detached shell around HD 179821 may be representative of environments that produce dust echoes from gamma-ray bursts.