An article to be published in the journal “Astronomy & Astrophysics” reports a study of the supernova SN 1987A that offers evidence that the explosion was decidedly asymmetric and dominated by two bipolar jets. A team of researchers led by astrophysicist Salvatore Orlando of the Italian National Institute of Astrophysics in Palermo has developed a model that takes into account the interaction between matter and magnetic field to study the evolution of SN 1987A. The results successfully reproduce the morphology of the iron-rich ejected materials, which was observed in particular by the James Webb Space Telescope. This shows that those structures are the result of an asymmetric explosion.
The image (S. Orlando et al., A&A, 2025) shows on the left the supernova SN 1987A remnant as seen by the James Webb Space Telescope, and in the other two panels the simulation of the density distribution of the remnant, which include the iron-rich materials, and the current morphology of that remnant.
The expansion of the materials ejected by the supernova underwent an extra acceleration due to the radioactive decay of nickel into iron, which heated the materials inside the supernova remnant. This increased the pressure, helping to form a sort of nickel bubble.
Supernova SN 1987A has been studied since it was first spotted. The explosion of a blue supergiant star in the Large Magellanic Cloud has been visible from Earth since February 23, 1987. Even after so many years, astronomers continue to study its consequences to obtain new information on the mechanisms at work in these extremely violent events, and even after the explosion, when the many ejected materials start dispersing at very high speeds in interstellar space.
Almost two years after the publication of the first results of observations of the supernova SN 1987A remnant with the James Webb Space Telescope, the analysis of that and other data allowed astronomers to obtain new answers about that event. This was achieved thanks to the development of a model of the evolution of that supernova.
The observations conducted with the James Webb Space Telescope’s NIRCam (Near-Infrared Camera) instrument were crucial for this new study. That’s because they revealed that the iron ejected from supernova SN 1987A wasn’t distributed homogeneously but rather concentrated in two separate clumps that were pushed outwards at very high velocities.
The researchers have two possible explanations for the asymmetry in supernova SN 1987A. The first explanation is based on the presence of violent instabilities caused by the neutrino flux in the progenitor star’s nucleus. The second explanation is based on magnetic fields and rotation combining to generate a bipolar explosion. However, at least for now, neither hypothesis can explain all the observed characteristics.
In essence, this new high-resolution 3D magnetohydrodynamic model (3D MHD) that combines the interaction between matter and magnetic field represents a step forward in understanding what happened in supernova SN 1987A, but not the end of the research. The predictions made by this model will be tested by comparing them with future observations using the XRISM space telescope. These X-ray observations will complement Webb’s by providing further information on the evolution of SN 1987A’s remnant.
