When A Star Reignites—ESA Finds That White Dwarf Can Cause Supernova Past Critical Mass
A dead star, such as a white dwarf that is no longer active in fusion and fission reactions, is essentially a ball of volatile cosmic gas. Waiting for a light to be matched, astronomers have long hypothesized that as such an intense concentration of combustible gases, that dead star can be set off like hidden mines by nearby stellar events. But until now, they've never found a smoking gun.
Publishing their results in the journal Nature, a group of researchers from London's University College at the Mill Hill observatory, detected radioactive nuclei generated by nuclear fission in the start of an interstellar cosmic blast. Observing a sun-like white dwarf who had shed its outer layer, condensing into an inactive core that under normal circumstances would cool off to nothing, the researchers discovered that when colliding with the added mass of another nearby solar system the carbon of the star's core would compress and cause an explosive supernova.
Known to be quite large, white dwarves can remain completely inert and stable under most conditions, a property known as the "Chandrasekhar limit". This mass limit, which has not been quantitatively determined as of yet, states that the weight of a white dwarf can in fact exceed what astrophysicist Chandrasekhar determined as stable by stealing mass from nearby stellar companions, resulting in an explosively nuclear outcome.
The specific supernova observed late last January 2014, later named "SN2014J", was of the la type and exploded in the nearby M82 galaxy, which is well-researched by London's Mill Hill teaching observatory. Though type la supernovas are common across the Universe, they are rather rare occurrences in any given galaxy, and offered the researchers an insightful look into a process that may not be documented again this generation.
In a type la supernova, theorists propose that the carbon and oxygen found in a white dwarf fuse to form radioactive nickel in a supernova event, which is twice the mass of the combined molecules and highly unstable. The cosmic explosion takes place when the nickel decays into radioactive cobalt before transforming yet again into stable iron. It is proposed that these type la supernova events are the cosmic sources of iron found on Earth and in our blood.
The explosion which emitted distinct cobalt decay signatures in its gamma-ray emission matched what researchers hypothesize happens in such white dwarf type la supernova events, however, as much data is still currently being collected by spacecrafts in the aftermath of the supernova explosion, researchers still hope to discover more information about the event and determine conclusively that their hypotheses have in fact been confirmed by the recent rare occurrence.
"It is perfectly consistent with the simplest scenario, of a single white dwarf with a mass close to the Chandrasekhar limit" European Space Agency astronomer Dr. Eugene Churazov said. "But we cannot exclude with this data as of yet that this event was caused by a merger [of two white dwarves]."