Supernova 1987A, a dazzling stellar explosion that occurred 36 years ago, has recently come under the scrutiny of the James Webb Space Telescope (JWST), providing astronomers with an unprecedented view of the evolving supernova remnant.
This particular supernova, the brightest one observed in the past 420 years, marked the explosive end of a blue supergiant star known as Sanduleak–69 202. Before its cataclysmic demise, this star was believed to have a mass about 20 times that of our sun.
Supernova 1987A, located approximately 168,000 light-years away in the Large Magellanic Cloud, was so luminous that it could be seen with the naked eye from the southern hemisphere. Astronomers have been monitoring its expanding debris since its discovery in 1987.
The JWST, equipped with its Near Infrared Camera (NIRCam), has now been used to study the supernova remnant. Led by Mikako Matsuura of Cardiff University, UK, this study aimed to measure the shockwave produced by the expanding supernova as it interacts with the surrounding material.
When massive stars like blue supergiants approach the end of their life cycles, they become unstable and begin ejecting substantial amounts of matter. Previously, the Hubble Space Telescope had observed as the expanding shockwave from Supernova 1987A collided with a ring of circumstellar debris that the star had ejected over thousands of years before its explosive demise. This collision caused the shockwave to slow down considerably.
Within this collision region, clumps of material became brighter, resembling a string of pearls. There were also two other fainter and thinner rings, appearing to be in a different plane from the main ring. Astronomers have speculated that these rings might result from interactions between the star’s stellar wind (emitted before the supernova) and previously expelled material. Alternatively, they might be illuminated by jets originating from an unseen neutron star that is believed to have formed during the supernova explosion.
The JWST observations have now provided fresh insights. The shockwave has extended beyond the main ring and accelerated, producing new hot spots that may become as luminous as the previously observed ones over time. There is also more diffuse emission in the form of a general glow, generated as the supernova blast wave excites the surrounding gas.
Notably, the JWST has detected two puzzling crescent-shaped features inside the main ring, which could represent the outer layers of gas expelled by the supernova but viewed at an angle.
The JWST will continue to monitor the evolving supernova remnant and search for the elusive neutron star at its center. While the neutron star itself has not been directly observed, indirect evidence, such as X-ray emissions detected by NASA’s Chandra and NuSTAR X-ray observatories, as well as observations from the Atacama Large Millimeter/submillimeter Array (ALMA), suggests it may be concealed within one of the dust clumps at the heart of the remnant.