Astronomers have obtained a detailed image of the Pa 30 nebula, the remnants of a supernova that was likely observed from Earth during the Middle Ages. The new photograph reveals structures that had previously gone unnoticed. Previous images of the explosion's remnants captured a sphere of long, filament-like strands of matter resembling fireworks or a dandelion. Observations made with the Gemini North telescope in Hawaii revealed about ten times more structures than any previous images of the supernova remnant. Researchers can now see that these filaments are shaped more like beads on a string, made up of pearl-like knots of gas of relatively uniform size.
These "cosmic pearls" are large, with each bead measuring about four light-days in diameter. Ilaria Caiazzo, a coauthor of the study published in The Astrophysical Journal, stated, "The planetary region of our solar system could fit in each knot about ten times with room to spare. The knots are quite strikingly uniform. We are excited to try to model them."
The formation of these pearls is not entirely clear, but they are assumed to be concentrations of material ejected during the explosion. The regularity of the knots is unusual, as astronomers expected to find more irregular shapes. This order could help researchers gain a deeper understanding of stellar death.
The Pa 30 nebula is notable because the central star is not completely dead; it is referred to as a "zombie star." Typically, a thermonuclear supernova results in the complete destruction of the star, but in rare cases, part of the star may survive. The unusual structures of Pa 30 could assist astronomers in reconstructing how these detonations occur and how zombie stars can continue to exist afterward.
The connection between modern observations and historical accounts is significant, as the nebula aligns with records from Chinese and Japanese astronomers in 1181, who described a new star in the sky that remained visible for several months. At that time, it was not known that they were witnessing the aftermath of a massive stellar explosion. Scientists later linked that event to the supernova that resulted in Pa 30.