Exploding supernova could be the "missing link" in understanding gamma-ray bursts (GRBs), one of the most powerful explosive events in the universe, according to new research. This finding could reveal secrets of the deaths of massive stars.
Supernova 2012ap was seen from Earth in 2012 as it exploded during the course of its death. Astronomers studying the remnants using the Very Large Array (VLA) of radio telescopes found that, although this event exhibited many of the characteristics of a supernova that would have produced a gamma-ray burst, no such release was detected. This marks the first time that such an event has been detected in the "middle ground" between GRB-producing occurrences and regular supernova.
These strange supernova release vast amounts of energy, but they are still not powerful enough to result in the production of gamma rays, the most energetic of all forms of electromagnetic radiation.
"This is a striking result that provides a key insight about the mechanism underlying these explosions. This object fills in a gap between GRBs and other supernovae of this type, showing us that a wide range of activity is possible in such blasts," said Sayan Chakraborti from the Harvard-Smithsonian Center for Astrophysics (CfA).
Supernova 2012ap is known as a "core collapse" supernova, which is the fate of all stars much more massive than our own sun. During these events, the star runs out of its final reserves of fuel, resulting in the collapse of the core into a neutron star or black hole. The middle and outer layers of the dying star then explode with tremendous force, spreading heavy elements to space.
During most supernovas of this type, the gas left over from the star expands outward in a nearly-spherical bubble at just a small percentage of the speed of light. These events do not possess the energy levels needed to produce gamma rays.
However, in a small percentage of cases, matter from the stellar body forms an accretion disk around the newly-formed black hole or neutron star, like water falling into a whirlpool. Charged particles can be driven by the magnetic field of the body, propelled away from the object at nearly the speed of light. This process, known as an engine, can result in gamma ray bursts.
Recent research suggests, however, that not all engine-driven supernovas result in the release of this powerful radiation, mostly composed of subatomic particles.
A supernova recorded in 2009 did not produce a GRB event, although the stellar remnant did exhibit high-speed jets. Astronomers believe its release may possess large concentrations of heavy particles.
"What we see is that there is a wide diversity in the engines in this type of supernova explosion. Those with strong engines and lighter particles produce gamma-ray bursts, and those with weaker engines and heavier particles don't," Chakraborti stated in a university press release.
Analysis of SN 2012ap and examination of how such events affect the development of gamma-ray bursts was profiled in The Astrophysical Journal.
Photo: NASA Goddard Space Flight Center | Flickr
