Following the explosion of Supernova 1987a, astronomers were eager to understand how it would evolve over time. Predictions ranged from the appearance of a pulsar to the interaction of the expanding gas cloud with earlier material ejected from the star. The resulting collision was expected to create a dazzling display reminiscent of sparkling diamonds. However, what astronomers observed instead was a peculiar string of pearls surrounding the site of the supernova.

Today, as scientists continue to study the aftermath of the stellar explosion, they have identified the cause behind the formation of the string of pearls. Known as the “Crow Instability,” this phenomenon occurs when vortexes off the wingtips of airplanes interact with engine contrails, breaking them up into a series of vortex rings. Michael Wadas, a graduate student at the University of Michigan, explains that this instability could be responsible for the unique appearance of the pearls surrounding Supernova 1987a. Wadas, who is now pursuing post-graduate research at CalTech, highlights the intriguing parallel between airplane wakes and the formation of the ghostly pearls.

About 1978a and its String of Pearls

Supernova 1987a, originating from the star Sanduleak -69 202 located approximately 168,000 light-years away in the Large Magellanic Cloud, marked a significant event in astronomy. It was classified as a Type II supernova, providing researchers with valuable insights into the mechanisms of core-collapse phenomena. As astronomers tracked the aftermath of the explosion, they observed a ring of ejected material and a shockwave expanding into space. Subsequently, the collision of this material with earlier stellar emissions resulted in the formation of the luminous pearls encircling the explosion site. The discovery of a neutron star at the center in 2019 further enriched our understanding of this cosmic event.

Capturing the attention of astronomers worldwide, the Hubble Space Telescope revealed bright rings surrounding Supernova 1987a months after its explosion. These rings, originating from the stellar wind of the progenitor star, were ionized by the ultraviolet light emitted during the supernova. The subsequent collision with the expanding ejecta in 2001 heated the inner ring, contributing to the emergence of the string of pearls. The shockwave generated from the explosion extended beyond the rings, leaving behind warm dust pockets and glowing gas clouds. The turbulent nature of this shockwave and its impact on the inner ring led to the creation of the mesmerizing pearls.

Competing Theories for the String

Various hypotheses have been proposed to explain the formation of the pearls around Supernova 1987a. While the Rayleigh-Taylor instability, arising from the interaction of fluids or plasmas of different densities, has been considered, it fails to fully account for the observed phenomenon. Instead, the Crow Instability, as suggested by Wadas and his colleagues in a recent publication in Physical Review Letters, offers a more compelling explanation. By simulating the effects of wind on a model cloud and its subsequent fragmentation, the researchers demonstrated how the Crow Instability could lead to the formation of a string of evenly spaced clumps, akin to the pearls observed around the supernova.

As astronomers continue to unravel the mysteries of Supernova 1987a and its intriguing string of pearls, the Crow Instability emerges as a promising avenue for further research. With recent observations from the James Webb Space Telescope revealing additional clumps within the ring, the potential for predicting similar formations in other cosmic scenarios, such as planetesimal formation around stars, becomes increasingly compelling. The evolving understanding of this cosmic phenomenon exemplifies the dynamic nature of research in astrophysics, offering new insights into the mechanisms underlying stellar explosions.

For More Information

Explaining a Supernova’s “String of Pearls”
Hydrodynamic Mechanism for Clumping along the Equatorial Rings of SN1987A and Other Stars