title: The changing morphology and increasing deceleration of supernova 1993J in M81
abstract: Twenty consecutive Very Long Baseline Interferometry images of supernova 1993J from the time of explosion to the present show the dynamic evolution of the expanding radio shell of an exploded star. High-precision astrometry reveals that the supernova expands isotropically from its explosion center. Systematic changes in the images may reflect a pattern of anisotropies and inhomogeneities in the material left over from the progenitor star. As the shock front sweeps up the material in the surrounding medium, it is increasingly decelerated and influenced by the material. After 5 years, the supernova has slowed to half of its original expansion velocity and may have entered the early stages of the adiabatic phase common in much older supernova remnants in the Milky Way Galaxy.
authors.affiliation: Department of Physics and Astronomy, York University, Toronto M3J 1P3, Ontario, Canada. National Radio Astronomy Observatory, Socorro, NM 87801, USA. Max-Planck-Institut fur Radioastronomie, D-53121 Bonn, Germany. Jet Propulsion Laboratory, Cali.
authors.initials: N
authors.lastname: Bartel
authors.initials: MF
authors.lastname: Bietenholz
authors.initials: MP
authors.lastname: Rupen
authors.initials: AJ
authors.lastname: Beasley
authors.initials: DA
authors.lastname: Graham
authors.initials: VI
authors.lastname: Altunin
authors.initials: T
authors.lastname: Venturi
authors.initials: G
authors.lastname: Umana
authors.initials: WH
authors.lastname: Cannon
authors.initials: JE
authors.lastname: Conway