Supernovae are known to be large explosions that occur at the end of the life cycle of a star but much about how they happen remains a mystery. Findings of a new study published in the journal Science on Jan. 30, however, could partly shed light on this mystery.

Study researchers  Dan Milisavljevic, from the Harvard-Smithsonian Center for Astrophysics, and  Robert  Fesen, from the Department of Physics and Astronomy at the Dartmouth College, studied the supernova remnant Cassiopeia A in a way that allowed them to come up with its three dimensional model that revealed large scale structures in the interior. The researchers described the interior of  Cassiopeia A as something that resembles a swiss cheese

"This is the first time we've actually seen such a complete image of what the interior of this thing looks like," Fesen said. "It shows big bubbles, big cavities that others suggested might be there, and this shows they really are."

The researchers unveiled a previous undiscovered trait that now indicates the star may have exploded differently than what astronomers believed. Scientists previously think that supernova explosions occur randomly with astronomers picturing dying stars as spherically symmetrical objects that collapse inward before they explode outward symmetrically as their remaining fuel is being burned up.

The researchers found evidence in the ejecta, the  material expelled in the stellar explosion, that suggests the explosion of the star was not random and that some of the star's symmetry or explosion led to the structures' formation. This finding suggests that stars do not behave as they were imagined before they explode.

The bubble-like interior of debris may have been produced by plumes of radioactive nickel that was generated during the star's explosion. Because this nickel will form iron when it decays, the researchers said that Cassiopeia A's interior bubbles should be have up to a tenth of the solar mass of iron.

Although such enriched interior debris has not been detected by prior observations, next generation telescopes may help with finding the missing iron and confirm the bubbles' origins.

"The remnant's interior has a bubble-like morphology that smoothly connects to and helps explain the multiringed structures seen in the remnant's bright reverse-shocked main shell of expanding debris," the researchers wrote in their study. "This internal structure may originate from turbulent mixing processes that encouraged outwardly expanding plumes of radioactive 56Ni-rich ejecta."

Cassiopeia A, which is located at in the constellation Cassiopeia, was formed 340 years ago with the explosion of a massive star that formed a neutron star.