NASA discovers thermonuclear blast in Deep Space

So was just recently listening the book "Supernova Era". It describes a star nearby earth but hidden by a dust cloud going supernova in the current time; but 200 years before it goes supernova, it produces a "helium flash" as all helium in the stars core is consumed in a few short minutes. The star then proceeds to fuse carbon produced from the helium flash. Is that what this event was? Should this pular be expected to erupt into a full blown nova sometime in the next thousand years as each of the
successively heavier elements are exhausted in their fusion cycle?

I mean of preserved things that perhaps solidified and maintained a structure that would inform someone that it was at one point entirely exotic radioactive substance.

but I’m think now that when these violent events happen, most of the ejecta is (by necessity of having to leave the large gravity well) extremely hot, and the time it takes to cool down and aggregate is also the time it takes to turn into something more boring isotope/element-wise

Betelgeuse is an enormous behemoth that has a volume of a billion suns, ready to explode. And it's not that far from us! We're safe though, we're not it the direction of the gamma ray beam, from the impending supernova. A supernova that will be so bright that it will outshine the moon!! It could happen tomorrow... Unfortunately, it could take a million years as well.

I read somewhere, I can't remember where though, that we're pretty safe from annihilating stars. Those who is ready to pop is either too far from us, or with their axis in a favourable direction.

So how many kilotons we talking here?

The sun produce about one trillion megaton per second, so about 864000000000000000000 megaton, 864 quintillion megaton, 864 septillioton. Basically nothing compared to a hypernova, that can emit as much light as the whole Milky Way galaxy (100-400 million stars) when it explode.

Back of napkin math... https://www.learnastronomyhq.com/articles/how-much-energy-does-the-sun-produce.html

In 1 second the Sun generates 3.8 x 1026 Joules. That is 3.8 followed by 26 zeroes. In the UK that is 380 quadrillion Joules every second and in short scale numbers it would be 380 septillion Joules. 

10 days x 86,400 seconds / day x 3.8 x 1026 Joules / second = 3.2832 x 1032 Joules

I'm no rocket surgeon, but that's alot.

Edit... kiloton conversion

1 kiloton[explosive] is equal to 4184000000000 Joules, so

7.84703633 x 1013 gigatons

There is a network of neutrino detectors across the planet that would give a short warning of a supernova - maybe 3 hours. One big enough to impact life on earth would produce a significantly large neutrino signal across the detectors.

The neutrinos are emitted during the core collapse, but before the shockwave reaches the star surface and starts emitting light.

Neutrinos move at like 99.999% c. So whether light can catchup depends on two factors:

a) the time head start neutrinos have due to the delay between the core collapse and the emitting of visible light.

b) the distance from the supernova to earth