The Remnant of Supernova 1993J in M81
A "movie" showing the development of the supernova 1993J remnant in M81
for the one-year period of September 1993 to September 1994. These images
were taken in the radio light; the first four at 3.6 cm wavelength, the
last one at 6 cm.
NRAO press release on this radio film of the SN 1993J remnant
Marcaide, J.M., Alberdi, A., Ros, E., Diamond, P., Shapiro, I.I.,
Guirado, J.C., Jones, D.L., Krichbaum, T.P., Mantovani,
F., Preston, R.A., Rius, A., Schilizzi, R.T., Trigilio, C., Whitney,
A.R., Witzel, A., 1995.
Expansion of SN 1993J.
Science, Vol. 270, Issue 5241, pp. 1475-1478 (12/1995)
A sequence of images from very long baseline interferometry shows that the
young radio supernova SN 1993J is expanding with circular symmetry. However,
the circularly symmetric images show emission asymmetries. A scenario in
which freely expanding supernova ejecta shock mostly isotropic circumstellar
material is strongly favored. The sequence of images constitutes the first
"movie" of a radio supernova.
The supernova remnant at 6.3 cm, September 1994.
Marcaide, J.M., Alberdi, A., Ros, E., Diamond, P.J.,
Schmidt, B., Shapiro, I.I., Baath, Davis, R.J., de Bruyn, G.,
Elósegui, P., Guirado, J.C., Jones, D.L., Krichbaum, T.P.,
Mantovani, F., Preston, R.A., Ratner, M.I., Rius, A., Rogers, A.E.E.,
Schilizzi, R.T., Trigilio, C., Whitney, A.R., Witzel, A., Zensus, J.A.,
Discovery of Shell-like Radio-Structure in SN1993J.
Nature, Vol. 373, Issue 6509, pp. 44-45 (1995)
SUPERNOVA explosions are poorly understood, partly because of difficulties
in modelling them theoretically(1), and partly because there have been no
supernovae observed in our Galaxy since the invention of the telescope.
But the recent discovery(2) of supernova SN1993J in the nearby galaxy M81
offers an opportunity to investigate the evolution of the remnant, and its
interaction with the surrounding interstellar medium, at high resolution.
Here we present radio observations of SN1993J, made using
very-long-baseline interferometry, which show the development of a shell
structure. This 8-month-old radio shell is the youngest ever discovered in
a supernova. The data suggest that the supernova explosion and the
expanding shell of the remnant have nearly spherical symmetry, with small
deviations where some parts of the shell are brighter than others. If these
deviations arise because of variations in the density of the shell, this
may reconcile earlier reports of symmetric radio emission(3) with the
observed optical asymmetry(4,5), as the density variations could easily
cause the latter. We infer that the radio emission is generated at the
interface(6-9), where the surrounding gas is shocked by the ejecta.
The images in these page were obtained with a global Very Long Baseline
Interferometer (VLBI) array of radio telescopes in Europe and North America.
Thanks to Eduardo Ros of the University
of Valencia, Spain, for providing the references !
Images of the Supernova 1993J in M81
Last Modification: September 24, 2000