Most astronomers today believe that one of the most plausible reasons we have yet to detect intelligent life in the universe is due to the deadly effects of local supernova explosions that wipe out all life in a given region of a galaxy. Cassiopeia A might have a rare killer type 11 star -a core collapsed hypernova that generates deadly GRBs, gamma ray bursts that may leading astyronomers and physicists believe may be resonsible for destroying much of existing life throughout the billions of galaxies that populate the universe.
While there is, on average, only one supernova per galaxy per century, there is something on the order of 100 billion galaxies in the observable Universe. Taking 10 billion years for the age of the Universe (it’s actually 13.7 billion, but stars didn’t form for the first few hundred million), Dr. Richard Mushotzky of the NASA Goddard Space Flight Center, derived a figure of 1 billion supernovae per year, or 30 supernovae per second in the observable Universe!
Cassiopeia A is a supernova remnant in the constellation Cassiopeia and the brightest and strongest astronomical radio source in the sky. It is believed that first light from the stellar explosion reached Earth approximately 300 years ago but there are no historical records of any sightings of the progenitor supernova, probably due to interstellar dust absorbing optical wavelength radiation before it reached Earth.
The best explanation is that the source star was unusually massive and had previously ejected much of its outer layers. In 1999, the Chandra X-Ray Observatory found a “hot point-like source” close to the center of the nebula that is quite likely the neutron star or black hole that had been predicted but not previously found.
Certain rare stars -real killers -type 11 stars, are core-collapse hypernova that generate deadly gamma ray bursts (GRBs). These long burst objects release 1000 times the non-neutrino energy release of an ordinary “core-collapse” supernova. Concrete proof of the core-collapse GRB model came in 2003.
It isn’t known if every hypernova is associated with a GRB. However, astronomers estimate only about one out of 100,000 supernovae produce a hypernova. This works out to about one gamma-ray burst per day, which is in fact what is observed.
What is almost certain is that the core of the star involved in a given hypernova is massive enough to collapse into a black hole (rather than a neutron star). So every GRB detected is also the “birth cry” of a new black hole.
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