Astronomers have determined that dead stars, or "white dwarfs," are capable of reigniting and exploding as supernovas.
The discovery solves a mystery surrounding the nature of a specific set of stellar explosions known as Type la supernovas.
Experts had theorized that white dwarfs could explode due to a disruptive interaction with a companion star. They never had the evidence to support this notion until recently, according to BBC News.
Astronomers have had the tools to detect radioactive nuclei being generated by nuclear fusion in the cosmic blast, but have had to wait for a supernova to explode nearby in order to begin their observations.
A star with the mass of the Sun sheds its outer layers towards the end of its life as its core shrinks down to become a white dwarf. Single white dwarfs will just cool off slowly overtime, according to BBC News.
This is also a maximum mass a white dwarf can remain stable, a property known as the Chandrasekhar limit, which was named after the Indian-American astrophysicist Subrahmanyan Chandrasekhar.
When a white dwarf steals matter from a stellar companion, or collides with another white dwarf, other extra weight can compress the carbon in the star's core until this element undergoes nuclear fusion.
"Within the last decade, some scientists have been challenging the (supernova) interpretation, suggesting that much or all of the soft X-ray diffuse background is instead a result of charge exchange," said F. Scott Porter of the Goddard Space Flight Center, Greenbelt, Md.
Charge exchange can take place between solar wind ions and neutral gases, according to Discovery News. When the two gases come together within the solar system, electrons can be stripped from the neutral particles, thus generating X-ray emissions.
A number of astronomers disagreed that this diffuse X-ray glow observed in all directions could be a phenomenon inside the solar system and not hot particles from 10 million year-old supernovae outside the solar system.
An international team of scientists were able to create an instrument called the Diffuse X-ray emission from the Local Galaxy (or DXL). The instrument is capable of distinguishing between the two scenarios, according to Discovery News.
Once they launched the instrument 160 miles in altitude atop a sounding rocket, or well above the Earth's atmosphere, the instrument was able to detect the amount of charge exchange occurring within interplanetary space.
The DXL was able to figure out that just 40 percent of the diffuse soft-X-ray emissions were generated by charge exchange after 5 minutes of observations on Dec. 12, 2012. The rest are coming from the Local Cloud from outside the solar system, meaning the Local Bubble is real and we did get hit by a series of supernovae some 10 million years ago.
"This is a significant discovery," said Massimiliano Galeazzi, of the University of Miami in Coral Gables, who led the team, according to Discovery News. "(It) affects our understanding of the area of the galaxy close to the sun, and can, therefore, be used as a foundation for future models of the galaxy structure."
Their research was published in the journal Nature.
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