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Nova or Supernova
This is a sequel to the post (01/19/2020) concluding: a supernova without verification is probably just a variable star.
However there are actually several variable star events which might be called a supernova given the weak definitions provided for these events.
There are several types of a nova event.
excerpt from Wikipedia:
A nova is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star, that slowly fades over several weeks or many months. Causes of the dramatic appearance of a nova vary, depending on the circumstances of the two progenitor stars. All observed novae involve a white dwarf in a close binary system. The main sub-classes of novae are classical novae, recurrent novae (RNe), and dwarf novae. They are all considered to be cataclysmic variable stars.
Classical nova eruptions are the most common type of nova. They are likely created in a close binary star system consisting of a white dwarf and either a main sequence, subgiant, or red giant star. When the orbital period falls in the range of several days to one day, the white dwarf is close enough to its companion star to start drawing accreted matter onto the surface of the white dwarf, which creates a dense but shallow atmosphere. This atmosphere, mostly consisting of hydrogen, is thermally heated by the hot white dwarf and eventually reaches a critical temperature causing ignition of rapid runaway fusion.
The sudden increase in energy expels the atmosphere into interstellar space creating the envelope seen as visible light during the nova event and previously mistaken as a "new" star. A few novae produce short-lived nova remnants, lasting for perhaps several centuries. Recurrent nova processes are the same as the classical nova, except that the fusion ignition may be repetitive because the companion star can again feed the dense atmosphere of the white dwarf.
Novae are classified according to the light curve development speed, so in
NA: fast novae, with a rapid brightness increase, followed by a brightness decline of 3 magnitudes — to about 1⁄16 brightness — within 100 days.
NB: slow novae, with magnitudes of 3, decline in 150 days or more.
NC: very slow novae, also known as symbiotic novae, staying at maximum light for a decade or more and then fading very slowly.
NR/RN: recurrent novae, novae with two or more eruptions separated by 10–80 years have been observed.
Some novae leave behind visible nebulosity, material expelled in the nova explosion or in multiple explosions.
(excerpt end)
my comment:
The supernova type Ia had been 'hotly debated' whether it was a white dwarf event but 'thermal runaway was the consensus. The 'classical nova' with its description of 'critical temperature causing ignition of rapid runaway fusion' is rather similar to a supernova type Ia.
The peak magnitude is never defined for the novae. The light curves use a range indicating these events are not consistent.
Not only do astronomers fail at explaining a supernova, they fail at explaining the nova as well using a similar ill-defined mechanism
If anything is in a 'runaway' mode then it must be in violation of thermodynamics and its conservation of energy. A system cannot create more heat when the internal system cannot (like from an exothermic chemical reaction)
This lack of distinction for a nova gets worse when looking at some variable star types.
From the list of variable star types:
"Dwarf novae are stars involving a white dwarf in which matter transfer between the component gives rise to regular outbursts."
This 'variable star' type of a 'dwarf nova' is much the same as others described above.
I suspect the fusion model being wrong results in many wrong explanations for any observed change in a star's brightness.
Many of these descriptions typically falter at either explosion or runaway.
One could hope a behavior like variability having an observed range can be explained without these extreme effects beyond a definable process conforming to physics.
The white dwarf is required for many explanations so this specific star type is critical in these particular behaviors in cosmology.
Perhaps only the variable star type of an eclipsing binary is not affected by the model used for the star.
Neither the nova nor supernova has a clear explanation for the observed variability.
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