The remains of a rare supernova have been discovered in our galaxy for the first time, raising new questions about the spread of key elements close to the center of the Milky Way. Though dramatic, supernovae aren’t necessarily uncommon, as stars tech their final evolutionary stages and go into runaway nuclear fusion. However, not all supernovae are created equal.
Typically – and in keeping with the remnants of supernovae in our galaxy – they’re so-called Type la supernovae. When white dwarf stars begin their final run on what remaining fuel is left, they can drag in material from a neighboring star or even merge with another white dwarf.
That produces a huge amount of light which, importantly, has been found to be effectively standard regardless of where each Type la supernova takes place. Though the most common, however, it’s not the only sort. Rarer Type lax supernovae are less potent in their explosions, and release differing amounts of elements that the star created over its life as part of its nuclear reactions.
This isn’t the first time a Type lax supernovae has been spotted, but it’s the first time one has been identified in our own Milky Way. “If we’re right about the identity of this supernova’s remains,” says Shing-Chi Leung of Caltech in Pasadena, California, co-author of a study that used data from NASA’s Chandra X-ray Observatory to flag the rare supernova, “it would be the nearest known example to Earth.”
Near is, of course, a relative term. The supernova remnant, known as Sagittarius A East or Sgr A East, is close to Sagittarius A*: that’ the supermassive black hole at the center of the Milky Way. Earth is more than 25,000 light years from that.
“Astronomers are still debating the cause of Type Iax supernova explosions, but the leading theory is that they involve thermonuclear reactions that travel much more slowly through the star than in Type Ia supernovae,” NASA explains. “This relatively slow walk of the blast leads to weaker explosions and, hence, different amounts of elements produced in the explosion. It is also possible that part of the white dwarf is left behind.”
It’s that nuclear reaction rate which helped the team – co-authored by Ping Zhou and Yang Chen of Nanjing University in China, Ken’ichi Nomoto of The University of Tokyo in Japan, and Jacco Vink of the University of Amsterdam in The Netherlands – to potentially classify Sgr A East as a Type lax supernova. Chandra was already examining Sagittarius A* and, from around 35 days of recordings, strange patterns of elements in the X-ray data were spotted. They implied the sort of slow nuclear reaction that’s indicative of the rarer supernovae.
The group published their work in The Astrophysical Journal today.
Supernovae are important because they’re the only source of certain key elements in the universe. Substances like iron, nickel, and chromium are generated in the intense nuclear furnace at the heart of a star, but only released once the white dwarf erupts and scatters those elements throughout the galaxy. Understanding how those patterns form, and the supernovae responsible for them, is believed to be key in explaining the underlying principles of the universe, its expansion, and the circumstances which helped life arise.