T Pyxidis is a binary star system in the constellation Pyxis at about 3260 light years from Earth. It contains a sun-like star and a white dwarf. The White dwarf might supernova in the next several million years.
Sion's team has reached the conclusion that T Pyxidis is about to go supernova (in this case, it would be a Type 1a supernova, destroying both stars).
During Sion's presentation, he was challenged by one of his peers in the audience, Prof. Alex Fillipenko from Berkeley Astronomy Department. Apparently Sion had possibly miscalculated the damage that could be caused by a T Pyxidis supernova.
It seems that Sion had used data for a far more deadly gamma-ray burst (GRB) exploding 3,260 light-years from Earth, not a supernova. T Pyxidis certainly isn't expected to produce a GRB. (Gamma-ray bursts are thought to only be generated by a massive star that has reached the end of its life as a Wolf-Rayet star collapsing under its own gravitational attraction.)
"A supernova would have to be 10 times closer [to Earth] to do the damage described," Ray informed me via email.
The scientists at the meeting were also highly dubious about Sion's estimate that the star could explode imminently.
Astronomy.com reports - A type Ia supernova (or "white dwarf supernova"), releases 10 million times more energy than a nova explosion, or is equivalent to 20 billion, billion, billion megatons of TNT.
Sion findings suggest the white dwarf, considered close to us by cosmic standards, could eventually go supernova. Gamma radiation emitted by the supernova could threaten the Earth with an energy equivalent to 1,000 simultaneous solar flares. The production of nitrous oxides in Earth's atmosphere by the gamma rays could completely destroy the ozone layer, astronomers said.
However, if others are right then the effect would be more like 1 to ten solar flares.