Approximately 6,500 light-years away from Earth, a peculiar zombie star is concealed within long, hot sulfur tendrils. The origin of these tendrils remains a mystery, but astronomers have now pinpointed their destination. Recent observations, published in the November 1 issue of Astrophysical Journal Letters, reveal the 3-D structure and movement of debris from a supernova that exploded nearly 900 years ago.
"It's a crucial piece of the puzzle in understanding this highly unusual supernova remnant," explains astronomer Tim Cunningham from the Harvard & Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
The supernova was initially documented in 1181 as a 'guest star' by ancient Chinese and Japanese astronomers. It wasn't until 2013 that astronomers identified the remnants of this explosion, now known as the Pa 30 nebula. When they did, the remnant appeared quite unusual. The supernova was believed to be of type 1a, where a white dwarf star detonates and obliterates itself. However, in this instance, part of the star survived.
What's even more perplexing is that the star was surrounded by spiky filaments extending about three light-years in all directions. "This is truly unique," Cunningham notes. "No other supernova nebula exhibits filaments like these."
Cunningham and his team utilized the telescope at the W.M. Keck Observatory in Hawaii to measure the speed at which these filaments move relative to Earth. They then constructed a 3-D model of the filaments and their movements through space. The team discovered that the system is structured like a 'three-layered onion.' The innermost layer is the star, followed by a gap of one or two light-years, ending in a spherical shell of dust. The outermost layer consists of the filaments, which emerge from the dust shell.
The exact formation mechanism of the filaments and their maintenance of straight-line shapes for centuries remains uncertain. One hypothesis suggests that a shock wave from the explosion might have ricocheted off the diffuse material between stars and rebounded toward the white dwarf, shaping the material into the observed spikes. Future theoretical studies leveraging these new observations could potentially unravel this mystery.
The study confirmed that this remnant is undoubtedly from the guest star of 1181. By analyzing the speeds and positions of the filaments and tracing them backward, researchers determined that they all originated from the same point around the year 1152, plus or minus 75 years.
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