Explosive power of a supernova?

  • #1

Main Question or Discussion Point

Supernovas (exploding stars) are the most power explosions known to science. They are so awesomely powerful, they actually tear holes in the fabric of reality (space time) and create black hole singularities. Approximately how many megatons are there in a supernova?

Are megatons (4.184×1015 J) even an appropriate unit to measure the power of the cosmic blasts? Yottatons, perhaps? What would happen to Earth and the rest of the solar system if our sun suddenly went supernova?

175872main_sn2006gy_main_330.jpg
 
Last edited:

Answers and Replies

  • #2
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
2019 Award
24,543
7,428
A typical unit is the FOE, short for 10-to-the fifty-one ergs.
 
  • #3
DaveC426913
Gold Member
18,784
2,268
What would happen to Earth and the rest of the solar system if our sun suddenly went supernova?
The sun is too small to go supernova. Stars that go supernova must be much larger. Sol will expand to a red giant, then dwindle to a white dwarf.
 
  • #4
FtlIsAwesome
Gold Member
191
0
What would happen to Earth and the rest of the solar system if our sun suddenly went supernova?
The sun is too small to go supernova. Stars that go supernova must be much larger. Sol will expand to a red giant, then dwindle to a white dwarf.
So to change the question slightly: What would happen to a planetary system around a massive star that goes supernova?--Can such stars have planets?
 
  • #5
Drakkith
Staff Emeritus
Science Advisor
20,860
4,606
Supernovas (exploding stars) are the most power explosions known to science. They are so awesomely powerful, they actually tear holes in the fabric of reality (space time) and create black hole singularities. Approximately how many megatons are there in a supernova?
This is incorrect. The supernova has nothing to do with forming the black hole. It is actually the opposite. The collapse of the core of a massive star causes a massive shock wave of neutrons and radiation which causes a "rebound" of the infalling matter outside of the core. This shockwave destroys the star and is the process behind a Supernova. In fact, many stars go supernova and do NOT form a black hole, but instead form a Neutron Star because their mass is not enough to cause the collapsing core to overcome the degenerate pressure of neutrons.

See here for more: http://en.wikipedia.org/wiki/Supernova#Core_collapse
 
  • #6
Drakkith
Staff Emeritus
Science Advisor
20,860
4,606
So to change the question slightly: What would happen to a planetary system around a massive star that goes supernova?--Can such stars have planets?
That depends on how close the planets were to the star and the power of the supernova, but I'd say its a very good bet that any planets near the star would be destroyed, while planets very very far away might survive but be ejected.
 
  • #8
181
0
Also, a Gamma Ray Burst is the most powerful explosion. A giant star collapses into a black hole converting the mass of the Sun into energy in one second.
 
  • #9
The sun is too small to go supernova. Stars that go supernova must be much larger. Sol will expand to a red giant, then dwindle to a white dwarf.
Mind you, that expansion is going to blast Earth to a cinder or destroy it entirely, along with the other inner planets. It won't be explosive, but considering that an expanding gas envelope alone can do that, if Sol were to defy physics and explode I think it's safe to say that the inner planets at least would be blown to bits.
 
  • #10
181
0
IIRC, the first exoplanets ever discovered were found obiting the pulsar remnant of a supernova.
 
  • #11
442
0
Supernovas (exploding stars) are the most power explosions known to science. They are so awesomely powerful, they actually tear holes in the fabric of reality (space time) and create black hole singularities. Approximately how many megatons are there in a supernova?

Are megatons (4.184×1015 J) even an appropriate unit to measure the power of the cosmic blasts? Yottatons, perhaps? What would happen to Earth and the rest of the solar system if our sun suddenly went supernova?

175872main_sn2006gy_main_330.jpg
Doesn't space-time singularity come into existence when a neutron star's collapses depending on the core remnant (TOV-limit) or by accretion induced collapse ?
I don't see how a supernovae directly leads to the formation of a BH,what I do know is that supernovae are crucial for the formation of SNR and heavier nuclei during the disintegration by r-process.Sun doesn't have enough mass to become a type II supernovae.For starters it's core is based upon the heaviest element being helium,super giants on the other hand need Iron/Fe as their densest element within the core.Iron being the most stable absorbs heat instead of radiating away which eventually leads to ideal condition for a supernovae to come into existence.

I just wanted to clarify a slight mis-information in your post which you may or may not be aware of.




EDIT: After having read few posts above me,I have been beaten! :( Oh no
Regards,
ibysaiyan
 
  • #12
Doesn't space-time singularity come into existence when a neutron star's collapses depending on the core remnant (TOV-limit) or by accretion induced collapse ?
I don't see how a supernovae directly leads to the formation of a BH,what I do know is that supernovae are crucial for the formation of SNR and heavier nuclei during the disintegration by r-process.Sun doesn't have enough mass to become a type II supernovae.For starters it's core is based upon the heaviest element being helium,super giants on the other hand need Iron/Fe as their densest element within the core.Iron being the most stable absorbs heat instead of radiating away which eventually leads to ideal condition for a supernovae to come into existence.

I just wanted to clarify a slight mis-information in your post which you may or may not be aware of.



EDIT: After having read few posts above me,I have been beaten! :( Oh no
Regards,
ibysaiyan
That is one way to achieve a black hole, and a neutron star is one possible outcome of a supernova. In the case of a star with an initial mass that is too great to allow for a neutron star, the supernova occurs, but the collapse involved continues and GR says there is no stopping it. You're left with an 'object' that cannot be supported by any known degeneracy pressure, and a singularity arises.

In theory, adding mass to a neutron star can lead to further collapse, but I wonder if you wouldn't have an explosive event that ejects mass too?

As far as Sol goes, its initial mass set the stage and what it fuses hardly matters; it will never have enough mass to undergo catastrophic collapse so the outer gas envelope will expand leaving a core of (mostly?) degenerate electron matter we call a white dwarf.
 
  • #13
jambaugh
Science Advisor
Insights Author
Gold Member
2,215
248
...They are so awesomely powerful, they actually tear holes in the fabric of reality (space time) and create black hole singularities.
Very poetic but "tearing a hole in the fabric of reality" is just plain nonsense. No offense intended but one does not need to add fancy to the already fantastic.

As far as cause and effect goes, it is more the formation of the black hole (or neutron star if there is insufficient mass for a BH) which "causes" the super-nova. As the red giant has exhausted its easily fused elements it begins contracting. At the center the density reaches that of atomic nuclei and a shock wave forms from this ultimate act of nuclear fusion, all atoms are compressed to a single super nucleus. The outgoing shock produces the super nova and the inner ball of neutronium if massive enough bends time inward forming a black hole.

There's no "tearing of reality", but rather a bifurcation (the formation of a fork in the road) of possible paths into the future, some lead inward toward what we can best describe in classical GR as a singularity, and some outward into the wide universe.
 
  • #14
About how many hydrogen bombs is a supernova equal to?
 
  • #15
About how many hydrogen bombs is a supernova equal to?
A thermonuclear bomb ranges from a megaton or so, to the largest being 50 megatons. The best measure for a supernova isn't megatons, as has already been mentioned. Supernovae are as varied as the stars which can produce them, from relatively small scales to hypermassive stars so you're using two sliding scales.

It's probably worth noting that the mechanism is the same in both cases however; release of energy due to fusion of elements.
 
  • #16
442
0
About how many hydrogen bombs is a supernova equal to?
Depends on the mass of the star but this number would be VERY LARGE in scale of hydrogen bombs.
 
  • #17
Depends on the mass of the star but this number would be VERY LARGE in scale of hydrogen bombs.
Perhaps billions of H-bombs?
 
  • #18
jambaugh
Science Advisor
Insights Author
Gold Member
2,215
248
Here's a "bar napkin" calculation:

The sun has stellar magnitude of -26.8 and is 1 AU = 1/63200 ly away and outputs about 4x10^26 watts of power.

Now consider SN1987A which occurred in the Larger Magellanic Cloud (and appeared in 1987.) It had a magnitude of +2.9 and was 16,000 ly away.

Now stellar magnitudes are a logarithmic scale. The difference in magnitudes gives us an exponent for calculating relative flux. The difference in magnitudes is -26.8 - 2.9 = -29.7. So the flux from the sun was 10^(-29.7/-2.5)~760,000,000,000 times that of the supernova. Of course the sun is closer. Since flux decreases with the square of distances and the supernova happened 16000*63200=1,011,200,000~1billion times farther away, its power output must have been:

1billion^2/760billion or about 1.3million times brigher. That's around 5x10^32 watts of output (1.3million times the sun's).

OK now to convert to a more meaningful number. A watt is a joule per second. c^2 =9x10^16 m^2/s^2 so figure about...

5.5x10^15 kg of mass units of energy per second.

Since a supernova shines for a day or so, say 18,000 seconds that's on the order of 10^20 kg of mass converted to energy. Now that's just radiant energy, one can figure there's energy output in the ejected matter and the supernova will shine for years at lesser intensity so a factor of 10 times this number is not out of the question.

Figure 10^20-10^21 kg converted to energy, that's say the mass of Tethys (a moon of Saturn) or about 10% of our moon converted to energy.

To compare that to nuclear (and chemical) explosives, a megaton (of TNT's explosive energy) = 4x10^15 joules is about 4.4 x10^(-2) kg or 44 grams mass energy equivalent.

So, well... there you go. (Oh and double check my bar napkin calculations, I did most in my head.)

[EDIT... I used: magnitude = 2.5 log(flux/base flux) where base flux is set so 0 magnitude is right at visible to the naked eye.]
 
  • #19
6,814
13
Also the 10^51 ergs is the amount that gets transferred to the explosion. The total gravitation energy that gets released is about 10^53 ergs, and 99% of that gets radiated away in the form of neutrinos.
 
  • #20
6,814
13
It's probably worth noting that the mechanism is the same in both cases however; release of energy due to fusion of elements.
It's not. The energy of a supernova comes from gravitation collapse. Most of the nuclear reactions in the supernova take up energy rather than produce it.

Also one 250 kiloton H-bomb = 10^22 ergs, so to get a supernova you need 10^29 H-bombs.

One billion is 10^9.

So you need one hundred billion billion billion H-bombs for one supernova.

And the total energy released is about 100 times that.
 
  • #21
jambaugh
Science Advisor
Insights Author
Gold Member
2,215
248
Also the 10^51 ergs is the amount that gets transferred to the explosion. The total gravitation energy that gets released is about 10^53 ergs, and 99% of that gets radiated away in the form of neutrinos.
So my "bar napkin" is several orders of mag. too small. :smile:
 
  • #22
It's not. The energy of a supernova comes from gravitation collapse. Most of the nuclear reactions in the supernova take up energy rather than produce it.

Also one 250 kiloton H-bomb = 10^22 ergs, so to get a supernova you need 10^29 H-bombs.

One billion is 10^9.

So you need one hundred billion billion billion H-bombs for one supernova.

And the total energy released is about 100 times that.
Ouch, and right you are, sorry!
 
  • #24
What about a gamma ray burst?
Seems to be part of the same process involving gravitational energy released during collapse; they just happen to be one part of that and directed in a polar fashion.

Wait, do you mean how many 250 KT nuclear weapons, or the process involved? If you mean the yield, then I don't know, and once again you're using two sliding scales. Ask yourself: is it more useful to think in terms of joules, eV, ergs, and other scientific units, or to equate all of this to a specific weapons yield based on tons of TNT? I'd say it's best to think in terms of joules or ergs, and you can relate that solid scale to everything from the output of a flashlight, Sol, a GRB, or the total output of a galaxy in a given time frame. After all, you don't really know what 250 KT to the 29th power means beyond a number, and neither do I. Think of this like learning how to use a keyboard; it's a pain to start out, but it's a good investment.
 
Last edited:
  • #25
6,814
13
Ask yourself: is it more useful to think in terms of joules, eV, ergs, and other scientific units, or to equate all of this to a specific weapons yield based on tons of TNT?
It's actually better to think in terms of things that will give you numbers between 1 and 100. I can imagine a 100 trees or seashells, and I can imagine the difference between 1, 10, 100, or 1000 of something.

I can't really imagine 10^28 of something. However, I can imagine 28.

I'd say it's best to think in terms of joules or ergs, and you can relate that solid scale to everything from the output of a flashlight, Sol, a GRB, or the total output of a galaxy in a given time frame.
It helps to think of two numbers. For supernova, the numbers are 1 and 51, both of which I can visualize since they are less than 100.
 

Related Threads on Explosive power of a supernova?

  • Last Post
Replies
1
Views
2K
Replies
13
Views
1K
  • Last Post
Replies
2
Views
5K
Replies
7
Views
3K
Replies
3
Views
2K
Replies
5
Views
1K
  • Last Post
Replies
6
Views
4K
Replies
8
Views
1K
Replies
40
Views
5K
Replies
1
Views
2K
Top