Best, Ian

I'm not working in the field of SNe, so I can't give you a perfect definition. Typical Sne are powered by the radioactive decay of heavy elements which are produced by runaway neutron accretion (r process) during the initial explosion. This is mostly Nickel 56, followed by Cobalt 56 (which has a longer half-life).

Early supernovae spectra are characterized by broad emission components reflecting the high expansion speed (up to 10% light speed for GRB-associated broad-line Type Ic SNe ["hpyernovae"]). After a few months, the SNe enter the so-called nebular phase, which feature strong emission lines from forbidden transitions.

To my understanding, a SNR is what the expanding shell of the explosion is called at a time when all the radioactives (except for rare, long-lived isotopes like actinids) have decayed (thus no longer powering em emission), and the only emission comes from the shock-heating of the interstellar medium at the collision front. This transition typically happens after one or a few decades. SN 1987A is giving us the first glimpse of a newborn SNR. Things like Cassiopeia A, Tycho's SNR and Kepler's SNR are typical for this phase.

SNR slowly peter out, diffuse, and disappear after a few million years. There's speculation that the the Local Interstellar Bubble the sun sits in is a ~ 2 million year old SNR, the brightest SN in human (pre-)history.

Hope that helps!

@Hunabku: Always fascinating how we mainstream scientists always turn out to be completeley stupid and just plain wrong in the long run, eh?

Black holes are not formed upon the death of the star – rather the exact opposite is true – the black hole is the first thing emerging upon the birth of the star. Do you see those counter spinning vortices in the graphic above? New observation reveal that inside stellar nurseries counter spinning vortices touch amidst the gases and dust. Where those vortices touch a black hole exists and it grows in size relative to the amount of matter and energy around it.

The star grows as its engine grows in a "balanced" feedback loop – exchanging energy/matter between the radiative component, that we eventually see and call the star, and the contractive black hole at the center. A super nova is when a very large star falls out of balance – and releases energy so as to emerge in a new order of stasis.

JT
/www.iurlz.com/demtools

I don't think there is an exact definition of when an event becomes a remnant – but it would be reasonable to draw the line when the spectral signature indicates the fusion reaction has shut down, or in many cases, when we can no longer observe the event in a broad enough em spectrum to tell.

Cheers, Ian

I must say, I am quite critical of their paper. While they present some nice spectra etc., they hardly discuss at all why they think the X-ray outburst is due to a waek jet and not the non-relativistic SN shock break-out, as claimed by Soderberg et al. (Nature). Several other prominent researchers also follow the shock break-out interpretation and have strongly criticized papers claiming XRO 080109 to be an actual X-ray flash.

Two little comments on Ian's article itself: One does not speak of "supernova remnants until many years after an SN. SN 2007uy is far from being a remnant! Furthermore, while (see the name…) it's clear SN 2007uy happened "the previous year", one should point out that it was discovered on December 30!! If people had just waited two more days before looking at NGC 2770, we would know it as SN 2008A, and SN 2008D would be SN 2008E. SN 2007uy was also caught early on, so less than two weeks passed between the discovery of the two events.