<p>You may want to look into the <em>Chandrasekhar limit</em>.</p>
<p>Dr. Chandrasekhar did his original work on this back in the early 1930's but received the Nobel Price in Physics in 1983.  <a href="https://www.nobelprize.org/prizes/physics/1983/chandrasekhar/lecture/" rel="noreferrer">On Stars, Their Evolution and Their Stability</a></p>

CC BY-SA 4.0
2020-07-04T19:20:46.923Z
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.
ProfRob
CC BY-SA 4.0
2020-07-04T17:38:37.060Z
2020-07-04T17:38:37.060Z
Tim Campbell
<p>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 &quot;Type II&quot; supernova that had been observed. It would have been apparent from the start that the sun was no a &quot;massive star&quot;. So since the late 40s/early 50s, it has been known that very large stars can explode, but that the Sun cannot.</p>

CC BY-SA 4.0
2020-07-04T19:43:09.817Z
I think it *is* Hoyle & Fowler's work, but some citations would be good.
ProfRob
CC BY-SA 4.0
2020-07-04T17:43:24.187Z
2020-07-04T17:43:24.187Z
James K
<p>I think the definitive work is that of <a href="https://ui.adsabs.harvard.edu/abs/1960ApJ...132..565H/abstract" rel="noreferrer">Hoyle &amp; Fowler (1960)</a>.</p>
<p>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 (<span class="math-container">$&gt;2\times 10^{9}$</span> K) and they argued that this could only be achieved for both mechanisms if the star is more massive than the Chandrasekhar limit of <span class="math-container">$5.8M_{\odot}/\mu_e^2$</span>, where <span class="math-container">$\mu_e$</span> 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.</p>
<p>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 <span class="math-container">$&gt;1.2M_{\odot}$</span> for all plausible compositions. They even then conclude that stars up to <span class="math-container">$10M_{\odot}$</span> may lose enough mass to avoid a Type I supernova and become stable white dwarfs.</p>
<p>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.</p>
<p>As an aside - I reminded myself of the plot of &quot;Songs of Distant Earth&quot; (I read it loooong ago). Clarke's story posits that the &quot;neutrino problem&quot; (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.</p>

CC BY-SA 4.0
2020-07-04T20:25:11.380Z
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
CC BY-SA 4.0
2020-07-04T20:27:29.320Z
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
CC BY-SA 4.0
2020-07-04T21:00:47.863Z
@WiggotheWookie no it wasn't.
ProfRob
CC BY-SA 4.0
2020-07-05T01:58:55.560Z
"The Joshua Factor" from 1986 is another SF story that hinges on the solar neutrino problem, but IIRC in that one the problem in that one is that the sun is going to "go out" unexpectedly, rather than explode (in fact the thriller aspect is that the core had already stopped fusing sometime before the 1960s, but the photosphere hadn't "gotten the memo" yet, or something like that).
hobbs
CC BY-SA 4.0
2020-07-05T17:08:27.987Z
well, the sun becoming a red giant also puts a damper on continued inhabitation of the planet. Its not like we can escape the fate. and a supernova is much more exciting for a story writer.
Polygnome
CC BY-SA 4.0
2020-07-06T05:24:18.407Z
@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
CC BY-SA 4.0
2020-07-06T07:32:36.853Z
@Polygnome The gradual increase of the Sun's luminosity will make the Earth uninhabitable in around a billion years, long before the Sun becomes a red giant. See https://en.wikipedia.org/wiki/Timeline_of_the_far_future I guess that's even less exciting. ;)
PM 2Ring
CC BY-SA 4.0
2020-07-06T14:41:49.150Z
As an aside, Fred Hoyle himself wrote some very entertaining science fiction stories, novels and plays.
antlersoft
CC BY-SA 4.0
2020-07-06T18:05:22.760Z
"it is implicit that the Sun could not explode as either type of supernova" seems like it should end with "because the sun is exactly 1 M (M was defined using our sun as the reference unit)".
mtraceur
CC BY-SA 4.0
2020-07-06T19:25:07.270Z
As an aside, the [solar neutrino problem](https://en.wikipedia.org/wiki/Solar_neutrino_problem) was effectively resolved in the late 1990s. Clarke lived to see this question answered — I wonder if he ever addressed it in a later interview.
Michael Seifert
CC BY-SA 4.0
2020-07-04T20:05:22.610Z
2020-07-04T20:18:23.447Z
2020-07-04T20:18:23.447Z
ProfRob
<p>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?</p>
<p>I ask because a while ago I read &quot;<em>The Songs of Distant Earth</em>&quot; 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 surprised that this was still considered a possibility in the 1980s but accepted it.</p>
<p>However, today I began reading &quot;<em>The Gods Themselves</em>&quot; by Isaac Asimov, written in 1972, and in it a character states that the Sun is too small to go supernova.</p>
<p>This confused me as I thought both Clarke and Asimov were both scientifically knowledgeable and informed.</p>
<p>I can find plenty of information online about how our Sun will likely end and why it won't go supernova but not any information 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)?</p>

CC BY-SA 4.0
2020-07-05T08:07:33.297Z
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
CC BY-SA 4.0
2020-07-05T10:15:47.893Z
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
CC BY-SA 4.0
2020-07-05T11:37:36.410Z
@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
<the-sun><supernova><history><stellar-evolution>
When was it worked out/discovered that our Sun can't go supernova?
Wiggo the Wookie
# When was it worked out/discovered that our Sun can't go supernova?

(Asked by: username_0 on 2020-07-04)

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 surprised that this was still considered a possibility in the 1980s 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 were both scientifically knowledgeable 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 information 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)?

**Tags:** the-sun, supernova, history, stellar-evolution
> **Comments:**
> **username_1**: 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.  
> **username_2**: 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.  
> **username_0**: @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.  

---

## 3 answers

### Answer by username_4 on 2020-07-04. Score: 37 | Accepted answer

I think the definitive work is that of [Hoyle & Fowler (1960)](https://ui.adsabs.harvard.edu/abs/1960ApJ...132..565H/abstract).

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.

> **Comments:**
> **username_0**: 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.  
> **username_0**: 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?  
> **username_4**: @WiggotheWookie no it wasn't.  
> **username_6**: "The Joshua Factor" from 1986 is another SF story that hinges on the solar neutrino problem, but IIRC in that one the problem in that one is that the sun is going to "go out" unexpectedly, rather than explode (in fact the thriller aspect is that the core had already stopped fusing sometime before the 1960s, but the photosphere hadn't "gotten the memo" yet, or something like that).  
> **username_7**: well, the sun becoming a red giant also puts a damper on continued inhabitation of the planet. Its not like we can escape the fate. and a supernova is much more exciting for a story writer.  
> **username_8**: @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.  
> **username_9**: @Polygnome The gradual increase of the Sun's luminosity will make the Earth uninhabitable in around a billion years, long before the Sun becomes a red giant. See https://en.wikipedia.org/wiki/Timeline_of_the_far_future I guess that's even less exciting. ;)  
> **username_10**: As an aside, Fred Hoyle himself wrote some very entertaining science fiction stories, novels and plays.  
> **username_11**: "it is implicit that the Sun could not explode as either type of supernova" seems like it should end with "because the sun is exactly 1 M (M was defined using our sun as the reference unit)".  
> **username_12**: As an aside, the [solar neutrino problem](https://en.wikipedia.org/wiki/Solar_neutrino_problem) was effectively resolved in the late 1990s. Clarke lived to see this question answered — I wonder if he ever addressed it in a later interview.  

---

### Answer by username_3 on 2020-07-04. Score: 8

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](https://www.nobelprize.org/prizes/physics/1983/chandrasekhar/lecture/)

> **Comments:**
> **username_4**: 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.  

---

### Answer by username_5 on 2020-07-04. Score: 5

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.

> **Comments:**
> **username_4**: I think it *is* Hoyle & Fowler's work, but some citations would be good.  

---

