The heliopause is our first line of defense against high-energy cosmic rays. The Van Allen belts would be our second line of defense.

Lose both, and huge numbers of mutations ensue.

From Kaler’s entry on Eta Carinae, (Page 77, Kaler, 2002) the stars are an 80 solar mass (O-Btype hypergiant) and a more evolved 60 solar mass (WR or B hypergiant star?) which lost alotofmass during itseruption in the 1840’s. This is the star that stars in as famous HST image where we see two huge speckled pink lobes of gas and the thin disk with the superluminous stars themselves hidden at the centre..

Any planets born or passing near it is in serious peril!

Any and all the most supermassive stars - especially thehypergiantand LBV’s noted above are highly unstable and are potential supernovas -or masive outbursts like Eta Car’s huge 1800’s event - almost anytime. They just don’t last long at all!

Red supergiants like Betelguex, Antares and the largest red supergiant VV Cephei arealso prime candidates while Wolf-Rayet (WR or W type stars) are also expected toend as supernovae. The closest example of a red supergiant likely to explode soon-ish is proabably Betelguex at between 300-500 light years away. Which is spectacularly near but safely far away.

The ones we need to really worry about are the binary white dwarf generated type I supernova. They can creep up in you because they come from dim stars or rather dim pairings of stars where one is a small normal star the other a white dwarf taking material from its partner until it can take no more and detonates. One could be very close and we wouldn’t necesarily know it’s there until too late.

By the way BA there’s grist for your book there! (Feel free to quote & attribute if you so wish!)

A star is essentially a stalemated tug-o-war between gravity pulling matter in and radiation blasting matter apart. The more massive the star the greater the radiation pressure and there is a point - the Eddington-Humphries Limit (I think so called?) where the radiation pressure is so fierce a star just can’t hold together enough to even form and blows apart.
This limit today is around the 150 solar mass mark or so I gather as a first approximation.

However, in the distant past - because of the lack of heavy elements*, the very first generation of stars were supermassive “Population III” behemoths up to about 300 times more massive than our Sun. These quickly went supernova (a slightly different way to later ones apparently) and lasted an astronomical eyeblink or less but their deaths seeded the cosmos with the first metallic elements whose presence then stopped later stars ever getting as big again. At least that’s the theory based on our current understanding, no population III star has yet been observed directly..

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* ‘Heavy elements’ here meaning anything other than the very, very lightest ones - to astronomers “metals” mean anything above helium!

Define “soon”
- Jack