Most massive star known is revealed by huge explosion

Space.com reports that a supernova first observed in 2007 was believed to be different by scientists because it was 50 to 100 times brighter than a usual supernova. Astronomers now believe that the star began with about 200 times the mass of our sun.

Known as SN2007bi, the supernova remained bright for a very long time. Astronomers were able to observe it for almost two years, which is much longer than typical supernovas stay visible, said Paolo Mazzali of the Max-Planck Institute for Astrophysics in Germany.

Astronomers analyzed its signature and confirmed that SN2007bi matches predictions that theorize a pair-instability supernova. The findings were published in the Dec. 3rd issue of the journal Nature.

There were many doubts that stars this large existed, said Norbert Langer, astronomer from the University of Bonn in Germany. He wrote an opinion essay on this finding in the same issue of Nature where he stated that stars this massive were not believed to be able to form in the universe. He also stated that scientists are now sure that a 200 solar mass star did indeed exist.

Pair-instability supernovas have reached the end of their life and used their main hydrogen supplies and helium, leaving an oxygen core. In smaller stars the core keeps burning collapsing into a Type II supernova when all that remains is iron, then leaves a back hole or neutron star.

With extreme massive stars, however, while still containing an oxygen core, very energetic photons are released which create electron pairs along with their anti-matter opposites called positrons. When the electrons and positrons collide they annihilate each other, reducing the pressure of the star so it collapses. Then, the oxygen core ignites in a nuclear explosion where the whole star is consumed leaving no remnant behind.

This rare type of supernova indicate that not many stars can become so large; a debate long in the running. Mazzali admits he never was a believer of such massive stars, but seeing these findings first hand have changed his perspective. The discovery of these supernova has brought on a new development in star formation.