Spoonfedrelativity.com was intended to take what I had managed to glean from reading about Relativity, and make it clearer. Unfortunately I ran into a problem. There seems to be major confusion and controversy on the subject even among the experts, and I found myself in disagreement with the consensus. I've been forced into a Quixotic role. Watch my videos and join me in my tenacious pursuit attacking windmills.
Sunday, January 17, 2016
Direction isn't important IF the assumption of Hubble's Law Holds
A supernova is a transient astronomical object whose intrinsic brightness is several (~seven to nine) magnitudes brighter than a classical nova.
Where supernovae lie in luminosity-timescale space.
That's it. The definition is purely in terms of observational characteristics with no physical interpretation overlaid to confuse the issue.
This point is one that's underappreciated by the public and especially astrophysicists. You should never, ever mix classification with physical mechanisms. The former always informs the latter. If you start working physical mechanisms into your definitions (e.g., a supernova is the explosion of a high-mass star), then you'll start biasing the interpretation of your observations and have a much harder time dealing with new trends in your data.
In addition to the above definition of supernovae, several other classifications have been developed, such as "Type I" (supernovae without hydrogen in their spectra) and "Type II" (supernovae with hydrogen in their spectra). Only through continued observation of trends in the lightcurves (variation in brightness with time) and spectra of supernovae were astrophysicists able to predict that a particular subclass of supernovae come from white dwarfs (so-called "Type Ia supernovae") while the remainder come from high-mass stars.