# When was it worked out/discovered that our sun can't go supernova?

As the title says, when did we realise with reasonable confidence that our star is not going to be going out in a supernova blaze of glory?

I ask because a while ago I read The Songs of Distant Earth by Arthur C. Clarke which was from 1986 (but based on an earlier story) and a plot point is that the sun went supernova. I was suprised that this was still consdiered a possibility in the 80s but accepted it.

However today I began reading The Gods Themselves by Isaac Asimov, written in 1972, and in it a character states that the sun is too small to go supernova.

This confused me as I thought both Clarke and Asimov where both scientifically knowledgable and informed.

I can find plenty of information online about how our sun will likely end and why it won't go supernova but not any imformation on how long we have known (and therefore whether Asimov was ahead of his time or Clarke was uninformed in a way that would suprise me)

• In "The gods themselves" Asimov proposes a fictional mechanism for supernova <well, I will not spoil your reading>. It was up to him to decide if the Sun is eligible. IMHO, his proposed mechanism may make the Sun hotter which can bring its own problems and IMHO better applies to his plot, but in no way leads to supernova. Then again, I am not Asimov. – fraxinus Jul 5 at 8:07
• Why do you make the assumption that Clarke must have been uninformed? Science fiction can contain fictional plot points, even if the author knows they can't happen in real life. – JBentley Jul 5 at 10:15
• @JBentley mainly because Clarke seems to favour a hard science fiction style and sticks to the facts and theories where he can. At least in the Clarke I've read. – Wiggo the Wookie Jul 5 at 11:37

I think the definitive work is that of Hoyle & Fowler (1960).

They argued that supernovae were produced by two possible mechanisms - what they called an implosion/explosion or an explosion within degenerate matter. Both of these mechanisms required very high internal temperatures ($$>2\times 10^{9}$$ K) and they argued that this could only be achieved for both mechanisms if the star is more massive than the Chandrasekhar limit of $$5.8M_{\odot}/\mu_e^2$$, where $$\mu_e$$ is the number of mass units per electron (1 for hydrogen, 2 for helium, carbon, oxygen, 2.25 for 56Fe etc.); otherwise it could achieve a degenerate state, supported by electron degeneracy pressure, and cool indefinitely without contracting any further.

In addition, they successfully identified these two types of supernovae with Type I and Type II supernovae and argued that very high mass stars accounted for Type II supernovae via the implosion/explosion mechanism, whereas the Type I supernovae arose from the ignition of degenerate material in less massive stars, but still larger than the Chandrasekhar mass, which is $$>1.2M_{\odot}$$ for all plausible compositions. They even then conclude that stars up to $$10M_{\odot}$$ may lose enough mass to avoid a Type I supernova and become stable white dwarfs.

Though it seems not to be explicitly stated in the paper, it is implicit that the Sun could not explode as either type of supernova.

As an aside - I reminded myself of the plot of "Songs of Distant Earth" (I read it loooong ago). Clarke's story posits that the "neutrino problem" (the lack of detected solar electron-neutrinos), which was a thing back in the 60s, was actually because something odd was going on in the Sun's core. So I don't think that Clarke was suggesting that under normal stellar evolutonary circumstances the Sun would imminently explode. Indeed it was well known at that time that the Sun should continue on its main sequence life for billions of years.

• Thanks. I must have misunderstood Clarke's use of the neutrino problem to mean the sun would explode much sooner than expected, rather than it would unexpectedly explode. – Wiggo the Wookie Jul 4 at 20:25
• But does this mean that at the time Clarke wrote SoDE it was generally thought the neutrino problem could cause a supernova despite Hoyle and Fowler's work? – Wiggo the Wookie Jul 4 at 20:27
• @WiggotheWookie no it wasn't. – Rob Jeffries Jul 4 at 21:00
• @WiggotheWookie It's not that people thought the neutrino problem might cause the sun to explode, it's just that it was a mystery at the time. That meant you could speculate, in a science fictional context, that it might indicate hitherto unknown physics that would cause the sun to explode. He knew that was very unlikely, but he wanted the sun to explode for his story and a genuine scientific mystery gave him license to make stuff up. – Mark Foskey Jul 6 at 5:24
• As an aside, Fred Hoyle himself wrote some very entertaining science fiction stories, novels and plays. – antlersoft Jul 6 at 14:41

You may want to look into the Chandrasekhar limit.

Dr. Chandrasekhar did his original work on this back in the early 1930's but received the Nobel Price in Physics in 1983. On Stars, Their Evolution and Their Stability

• I'm not sure that Chandrasekhar would have fully (or even partially) understood the evolutionary processes that lead to a white dwarf or that they were the end states of low-mass stars, or what a supernova was.. However, it is certainly true that he established (also E C Stoner) that a $1M_{\odot}$ star could be supported indefinitely by electron degeneracy for any reasonable composition. So +1. – Rob Jeffries Jul 4 at 19:20

It would be my understanding that the work by Hoyle in the late 40s to early 60s established a mechanism by which massive stars could supernova, and so explain the "Type II" supernova that had been observed. It would have been apparent from the start that the sun was no a "massive star". So since the late 40s/early 50s, it has been known that very large stars can explode, but that the Sun cannot.

• I think it is Hoyle & Fowler's work, but some citations would be good. – Rob Jeffries Jul 4 at 19:43