I'm building a S-Type binary system where the primary star is a black hole. Yet the system formed as a O + K-Spectral class binary and the 20 solar-mass O giant went nova 2,7 myr after both the stars had transitioned from T Tauri tars to the main sequence after ca. 50 myr, like our sun did. Planets around the 0.78 solar-mass K-Type star should have almost reached their final composition and masses at that time. When the supernova happened the K-Type star was 2,8 ly away from it's partner. Assume that the systems plane of the ecliptic was aligned with the O-Giant.

What where/are the immediate and long term effects of the supernova on the system?

Edit: Added the hard-science tag after the first answer, because I would like to see some numbers backing up peoples claims. Some back the envelope calculations would suffice, no need for complex math.

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    $\begingroup$ The components of multiple star systems won't be separated by 2,8 light years anyway. The most distant known orbits of two stars in a multiple star system are HD134439 & HD134440 separate by 0.56 plus or minus 0.25 light years, and the system is considered to be unstable, despite being only 0.1107 to 0.2892 as wide as 2.8 light years. en.wikipedia.org/wiki/List_of_star_extremes I was shocked to learn that any binary star has so great a distance between components. $\endgroup$ Jun 26, 2019 at 15:05
  • $\begingroup$ @Thanks for pointing that out. I calculated the primaries hill-sphere and thought as long as the secondary is inside it, everything will be fine. With this in mind I'll ditch the idea of the system beeing a binary system and settle for a nearby black hole with a high relative velocity in order to avoid supernova issues. How do I delete this now useless question? $\endgroup$ Jun 27, 2019 at 9:04
  • $\begingroup$ As what-if.xkcd.com/73 says, even neutrinos from supernova cause a measurable radioactivity dose at that distances. May be a "simple" nova would be enough? $\endgroup$
    – ksbes
    Aug 1, 2019 at 6:47
  • $\begingroup$ Worth noting: though they’re often depicted as a single ‘wave’ that arrives then passes a supernova event would probably be more like bathing in a sea of hard radiation for a few days. Pack sunscreen. $\endgroup$
    – Joe Bloggs
    Aug 1, 2019 at 12:40
  • $\begingroup$ @ksbes, there is a big difference between 1 AU and 2.7 light years. Life is toast, but neutrinos aren't going to be the ones doing the cooking. $\endgroup$ Aug 2, 2019 at 0:04

1 Answer 1


At only 2.8 light years away, life is toast.

Most scientists believe that the minimum safe distance from a super nova would be around 200 light years away. As close as you're talking, it's probable that the energy release would sterilise any planets around your star system, so life (if it was forming or had formed) no longer exists.

From a practical perspective, what happens to the rest of the solar system artefacts (the suns and the planets) is kind of irrelevant as there is no-one on these planets to see it; even visitors would find these planets barren and hostile, for instance. I suspect that the energy release would strip the atmospheres away from the planets in the first instance, and while they may reform over time, this puts some pretty severe limits on life reforming as well. As for the stars, it's likely that they will also be impacted, but it's unclear as to how. At that distance, the material and energy released could easily disrupt a star and cause massive coronal mass ejections (CMEs) that in turn would cook any planets close in that may have otherwise survived the super nova. While it's possible that a star could be disrupted by having a large percentage of its gases stripped away this is unlikely because of the local gravity well and magnetosphere it generates.

But the thing is, EVERYTHING about a supernova is big. It's hard to conceive of an explosion on that scale and properly understand it. At that range, some stars may well be destroyed but it's important to note that most stars in the core of our galaxy are probably that close to each other and supernovae would have to have gone off many times in that region in the past, and the stars are still shining (or at least their light is still reaching us). So, it's possible that the celestial bodies of your solar system may survive in some form. But life on the other hand at that range is done for.

In point of fact, there's a theory around the timing of mass extinctions on Earth that pretty much says that the chances of a mass extinction while the solar system is actually passing through the lateral disc of the galaxy (as well as orbiting, it wobbles up and down on the Z axis) is around 1 in 2, or 50%. We just passed through that disc about 1 million years ago so we're not thought to be at risk for another 29 million years or so but the very existence of that theory tells us that being in close proximity to other stars is very dangerous to us as lifeforms. All it takes is a single star to go nova close enough to us and not even bacteria can survive on the surface of the earth.

So, while certain celestial bodies may still exist, in the long term their chances of harbouring life again within another million years or so are close to zero.

  • $\begingroup$ I think you underestimate how early this supernova happens. If the system where on the same timescale as earth water on Earth and the moonforming impact are still millions of years in the future when the supernova happens. This happens in the very beginning of the Hadean eon. Life is totally irrelevant in the context of my question, since the all the potentially habitable planets where lava worlds at the time. $\endgroup$ Jun 26, 2019 at 13:42
  • $\begingroup$ Many thousands of binary stars are known, but the widest known separation between components if far less than 2.8 light years, and so in a real binary system the effects of the supernova on the other star and the planets will be much greater than Tim B II calculated. $\endgroup$ Jun 26, 2019 at 15:07
  • $\begingroup$ To put in some numbers, the average supernova puts out one FOE of energy, which is 1.0e44 Joules (defined to be about the energy of a supernova). At a distance of 2.8 LY, that makes 11.3 Gigajoules per squaremeter on any surface in your target system. It will definitely not vaporize planets or affect the sun, but for fully developed life it will be problematic at least. It will greatly depend on the form of energy and time of release. $\endgroup$ Aug 5, 2019 at 14:13

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