In a distant region of space, a visually striking cosmic formation, resembling a "cosmic weed," is emitting material from its core at extraordinary velocities. For nearly 900 years, the origins of this massive cosmic explosion remained a mystery. Recent advancements in telescope technology have now offered an unprecedented view of its aftermath.
The formation, known as the Pa 30 nebula, features an unusual shape. In 2023, astronomers from Dartmouth College and Louisiana State University described the expelled material from the explosion as forming filaments, which extend outward from the center like a dandelion’s puff. Following this research, additional astronomers have succeeded in mapping these filaments for the first time.
Interest in the Pa 30 nebula can be traced back to 1181 when Japanese and Chinese astronomers noted the appearance of a new star, which disappeared after six months. In 2013, amateur astronomer Dana Patchick discovered a nebula in the Cassiopeia constellation, approximately 7,500 light-years from Earth, using images from NASA’s Wide-field Infrared Survey Explorer, an infrared space telescope. In the decade since, scientists have deduced that the Pa 30 nebula is likely the remnants of a supernova observed by ancient astronomers.
Nebulae are luminous and often large accumulations of matter, such as ionized gas and space dust, with some being remnants of stars that ended in explosive deaths. This is the case with the Pa 30 nebula, which exhibits some characteristics that are rare among known nebulae. At its center lies a remnant of its progenitor star, featuring a surface temperature of 360,000 degrees Fahrenheit (200,000 Celsius), vastly exceeding that of the Sun at roughly 10,000 degrees Fahrenheit (5,500 Celsius). Furthermore, the star is expelling material at an incredible speed of 620 miles (1,000 kilometers) per second.
According to Tim Cunningham, a NASA Hubble Fellow at the Harvard and Smithsonian Center for Astrophysics, the material within the filaments is expanding in a ballistic manner, indicating it has neither decelerated nor accelerated since the explosion. By analyzing the measured velocities, scientists can trace the explosion back almost precisely to the year 1181.
Cunningham and his team aimed to better understand the filaments’ structure. They utilized the Keck Cosmic Web Imager (KCWI) in Hawaii, which detects light in the visible spectrum. By analyzing the differences in energy between colors, such as blue and red, astronomers could determine which materials were moving toward or away from Earth. This analysis resulted in a three-dimensional map of the nebula’s filaments. The asymmetrical shape suggests that the original explosion was also asymmetric, with a curious void, up to 3 light-years wide, existing between the star remnant and the filaments. The void likely resulted from the explosion obliterating matter that was in close proximity to the center. It is worth noting that the Pa 30 nebula is not unique in exhibiting an unusual shape.
Christopher Martin, a Caltech physics professor and contributor to the study published in The Astrophysical Journal Letters, likened a typical image of a supernova remnant to a static photograph of a fireworks display. In contrast, KCWI provides insights akin to a "movie," capturing the motion of the explosion’s remnants as they travel outward from the central event.
The lingering question is the reason behind the nebula’s distinctive shape. Cunningham speculated that a shock wave may have compressed the speeding dust into beams, although this remains uncertain. Nearly a millennium later, some mysteries still defy resolution.