SN 2006gy: Possible Quark Nova
Supernovae (SN) usually occur when massive stars exhaust their fuel and collapse under their own gravity. In the case of SN 2006gy, however, a very different effect may have triggered the explosion. SN 2006gy and its host galaxy NGC 1260 are located in the Perseus Cluster of galaxies, part of the Pisces-Perseus Supercluster.
The SN 2006gy – discovered by Robert Quimby in 2006 August, has challenged our understanding of stellar evolution. SN 2006gy was 100 times more luminous than a typical SN and at the time the most energetic ever recorded. For almost a year it continued to radiate at a rate in which an ordinary SN could only sustain for at most a few days. The superluminous SN was too bright in visible light for Type-II supernovae produced by most massive stars, and it produced relatively few x-rays for Type Ia supernovae, which means SN 2006gy may have originated from an extremely massive star.
Massive stars with 130 – 250 solar masses produce high-energy gamma rays that can convert some of the energy into matter and anti-matter pairs (mostly electron-positron pairs). Instead of mass being converted to energy in the star’s core, energy is being converted to mass (nickel-56). The resulting drop in pressure causes the star to shed some of its outer layers in a large eruption, and collapse – earlier than expected during the luminous blue variable (LBV) phase. Pair instability supernovae are luminous enough but they seem to have a slow rise, and core collapse.
However, there’s an alternative, more exotic explanation. Subsequent study of SN 2006gy suggests that it underwent a neutron star (NS) to quark-nova (QN) stage. A quark nova, is the explosion driven by phase transition of the core of a neutron star to the quark matter phase leading to the formation of a quark star (QS). The collision between material ejected through the QN explosion and the preceding stellar envelope could basically re-brighten the SN, which means it could radiate at higher levels for longer periods of time.
Check out the links below for more information:
- Quark Nova Project
- List of
scientific papers on compact stars in the quark matter
- Cassiopeia A’s neutron star