Hottest temperature in universe

[Tom Mazanec]

What is the hottest the universe naturally gets?
I am thinking it is the center of an exploding supernova, is that right?

[Noclevername]

The first instants of the Universe were the hottest: BB. We're still basking in its afterglow.

[Tom Mazanec]

The first instants of the Universe were the hottest: BB. We're still basking in its afterglow.

I meant at present time.

[cosmocrazy]

The centre of a black hole?

[Noclevername]

I meant at present time.

Inasmuch as a Universe without simultaneity can have a "present time". I'd say probably a SMBH mergence. If a black hole can be said to have a "temperature".

[Tom Mazanec]

Inasmuch as a Universe without simultaneity can have a "present time". I'd say probably a SMBH mergence. If a black hole can be said to have a "temperature".

I thought SMBHs actually had ridiculously LOW temperature? At least for googles of years until the last second before they evaporate?

[Noclevername]

I thought SMBHs actually had ridiculously LOW temperature? At least for googles of years until the last second before they evaporate?

Low external, maybe?

[Noclevername]

If not BHs, then Gamma bursters.

[ngc3314]

Physicsy trivia: there is a maximum temperature a substance (well, by then it's an equilibrium mix of elementary particles and photons) can be heated up to , the Hagedorn temperature, around 2x10¹² K. Above that, the kinetic energy of particles gets transferred into more particles via pair production; it is possible that quark matter could absorb more energy but not even theoretically certain, AFAICT. (The very early Universe could have cheated this by not heating particles or having time for this process to occur).

Warning: sketchy explanation, many discussions veer into the string-theory consequences.

[Tom Mazanec]

From Wikipedia:
The Planck temperature is defined as:

{\displaystyle T_{\text{P}}={\frac {m_{\text{P}}c^{2}}{k}}={\sqrt {\frac {\hbar c^{5}}{Gk^{2}}}}\approx } {\displaystyle T_{\text{P}}={\frac {m_{\text{P}}c^{2}}{k}}={\sqrt {\frac {\hbar c^{5}}{Gk^{2}}}}\approx } 1.416808(33)×1032 K where:

mP is the Planck mass,
c is speed of light in a vacuum,
{\displaystyle \hbar } \hbar is the reduced Planck constant defined as {\displaystyle \hbar \ ={\frac {h}{2\pi }}} {\displaystyle \hbar \ ={\frac {h}{2\pi }}},
k is the Boltzmann constant,
G is the gravitational constant.
The two digits between the parentheses are used to denote the standard error of the last two digits of the estimated value.[4]

Significance
As with most of the Planck units, a Planck temperature of 1 (unity) is a fundamental limit of quantum theory, in combination with gravitation, as presently understood. In other words, the wavelength of light emitted by an object can be calculated by its temperature. If an object were to reach the temperature of 1.42×1032 kelvin (TP), the radiation it would emit would have a wavelength of 1.616×10−35 m (Planck length), at which point quantum gravitational effects become relevant. At temperatures greater than or equal to TP, current physical theory breaks down because we lack a theory of quantum gravity.[5]

[Ufonaut99]

I am thinking it is the center of an exploding supernova, is that right? ... I meant at present time.

If, by present time, we can include anything post-last-scattering (ie since around 379,000 years), then we can include the first stars. Being mostly hydrogen (without the metals that today’s stars start off with), they would have grown BIG, bright and hot (and Really short-lived - barely a million years IIRC) - and their supernovae would have dwarfed those of today.

I just found that SciAm have publicly posted their article about the first stars here : https://www.scientificamerican.com/a...ars-in-the-un/

Aside from supernovae, I wonder how hot colliding neutron stars would get - say that one detected by LIGO ?

For man-made devices, I thought offhand the hottest would be the National Ignition Facility (now there’s some frickin’ laser beams , all blasting a small nugget !), but turns out it only gets to a measly 100million degrees (I assume Celsius), and is overtaken by the Large Hadron Collider at 5.5 trillion Celsius (http://blogs.nature.com/news/2012/08...omic-soup.html) - hotter than supernovae, (but as ngc3314 notes, it’s not really the same substance after the collision )





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[Tom Mazanec]

Well, by present I meant like at 13.8 billion years.
I think hyperpowerful cosmic rays might be hotter at the collion-with-an-atom point, so let's say over an extended volume like one cubic meter.
Looking on Wikipedia I came up with these:

700 GK in quasars' accretion discs
740 GK, Hagedorn temperature or Fermi melting point of pions
1012
1 TK 0.1–1 TK at new neutron star
0.5–1.2 TK, Fermi melting point of hadrons into quark–gluon plasma
3–5 TK in proton–antiproton reactions
3.6 TK, temperature at which matter doubles in mass (compared to its mass at 0 K) due to relativistic effects
5.5 TK, highest man-made temperature in thermal equilibrium as of 2015 (quark–gluon plasma from LHC collisions)[12]
10 TK, 100 microseconds after the Big Bang
45–67 TK at collapsar of a gamma-ray burst
300–900 TK at proton–nickel conversions in the Tevatron's Main Injector[clarification needed]
1015
1 PK 0.3–2.2 PK at proton–antiproton collisions
2.8 PK within an electroweak star

1018
1 EK 2–13 EK at heavy nuclear conversions in the Large Hadron Collider
1021
1 ZK Dark matter at active galactic nuclei
1024
1 YK 0.5–7 YK at ultra-high-energy cosmic ray collisions
1027
103 YK Electrocoloral excitations
everything 10−35 seconds after the Big Bang
1030
106 YK Hagedorn temperature of strings
1032
108 YK 142 million YK, Planck temperature of Planck particles and geons or kugelblitzes
everything 5×10−44 seconds after the Big Bang; also predicted likely range of absolute hot
1033
109 YK Theory of everything excitations[citation needed]
Extradimensional gauge freedom[citation needed]
Landau poles[citation needed]
… …

[publiusr]

If an x-ray jet from a quasar hit a planet, that heat might build up quickly, but without a supernova shock wave blowing everything apart--so in terms of a planet just getting hot--that is probably the best mechanism.

[Jens]

For man-made devices, I thought offhand the hottest would be the National Ignition Facility (now there’s some frickin’ laser beams , all blasting a small nugget !), but turns out it only gets to a measly 100million degrees (I assume Celsius), and is overtaken by the Large Hadron Collider at 5.5 trillion Celsius (http://blogs.nature.com/news/2012/08...omic-soup.html) - hotter than supernovae, (but as ngc3314 notes, it’s not really the same substance after the collision )

Actually, I think it is Kelvin, though it's the same thing.

[Ufonaut99]

Actually, I think it is Kelvin, though it's the same thing.

. Reminds me of a story I heard that went something like this :

A journalist asked a professor “given how flat the observable universe is, in metric units what would be the minimum size of the entire universe?”

The professor replied “it must be at least 10 to power of 30”

The journalist asked “would that be in centimetres or kilometres?”

It was only after the professor gave him a strange look that he realised that that difference in scale was insignificant to the answer !



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[Jens]

Or there's also the joke about the museum guide who was showing guests around, and said,

"This skull is from a human that lived 1.8 million and four years ago."

One of the visitors is astounded and asks, "Jeez, how do you know the date so precisely?"

And the guide answers, "Well, when I started working here four years ago, my predecessor told me it was 1.8 million years old..."

[Jean Tate]

A bit late, and a bit nerdy ...

What do we - folks who've posted to this thread - mean by "temperature"?

If I remember my university physics, it is the inverse of the "n" in an expression that is, at its heart, e^n. In turn, that is related to the (relative) number of occupied energy states; yeah, there are caveats galore, but I think this capture the essence. Oh, and 0K is where the only occupied states are the lowest.

From this, it follows that where there is a "population inversion", temperature (in K) becomes negative. As in lasers, masers, etc. Which means, among other things, that when the blue light laser in your computer's HDD starts, it goes through a state with a temperature of ∞K.

Of course, masers exist in nature, so in one (very nerdy) sense, the answer to the OP's question is ∞.

[Tom Mazanec]

i meant a less nerdy sense, Jean Tate.
And BTW, how do you type things like that infinity symbol?

[Roger E. Moore]

Of course, masers exist in nature, so in one (very nerdy) sense, the answer to the OP's question is ∞.

Personally I am intrigued by this nerdy answer. Will do some research.

[Jean Tate]

i meant a less nerdy sense, Jean Tate.

Thanks for that.

May I ask, in terms of physics, what would you say “temperature” means, in the non-nerdy sense of your OP?

And BTW, how do you type things like that infinity symbol?

I wrote it using my MacBook, and DDG-ed how to write the infinity symbol ... option5 (DDG? I use DuckDuckGo, because it doesn’t bubble me).

[Jean Tate]

Personally I am intrigued by this nerdy answer. Will do some research.

My exceedingly bad memory tells me that one starts with the zeroth law of thermodynamics, and work your way to statistical mechanics, where you encounter \beta. Which, modulo a constant or two, is inverse temperature.

An important concept is “equilibrium”. In some parts of of astrophysics, you’ll encounter “LTE”, local thermodynamic equilibrium. In systems which are not in LTE, “temperature” may be a somewhat slippery thing ...

[Copernicus]

One poster on here said a black hole has absolute zero temperature, in a real sense, in that it does not transfer energy.

[Noclevername]

One poster on here said a black hole has absolute zero temperature, in a real sense, in that it does not transfer energy.

Depend on whether or not Hawking radiation is a thing.

[Strange]

One poster on here said a black hole has absolute zero temperature, in a real sense, in that it does not transfer energy.

A back hole both absorbs and radiates energy, as a black body.

In fact a small enough black hole can have a very large temperature: a 1ug black hole would have a temperature of about 10³² K.

Of course, we don't know if black holes of that size exist. But I assume the temperatures in accretion disks and jets can get quite extreme (about 10¹³ K accordion to this: https://www.space.com/32467-black-ho...-expected.html)

[Tom Mazanec]

I meant temperature as the temperature here is 20 C today, or the temperature of the star's photosphere is 9000 K, not the nerdy meaning that gives -200 K or plus infinity.

[Jean Tate]

I meant temperature as the temperature here is 20 C today, or the temperature of the star's photosphere is 9000 K, not the nerdy meaning that gives -200 K or plus infinity.

Thanks.

Both are systems of particles (atoms, molecules, ions, etc) and radiation (photons); in both the accessible energy states are populated and the distributions are close to equilibrium. So, in principle, one could determine a temperature from the those distributions.

Looking at some of the "hottest temperature in the universe" candidates mentioned in this thread so far:

* Planck temperature: speculative, as there is no good theory combining/consistent with both QFT and GR
* 5.5 TK, highest man-made temperature in thermal equilibrium as of 2015 (quark–gluon plasma from LHC collisions): good one; a quark-gluon plasma, created by colliding lead nuclei in the LHC, exists for long enough for the quarks and gluons to reach equilibrium (or close enough)
* a 1ug black hole would have a temperature of about 10³² K: speculative, both because there is no good theory combining/consistent with both QFT and GR, and because there's no evidence that such black holes exist in the post-surface of last scattering universe
* 1 ZK Dark matter at active galactic nuclei: highly speculative; we don't even know that dark matter is particles (and not, say, a feature of gravity we don't know about yet)
* 1 YK 0.5–7 YK at ultra-high-energy cosmic ray collisions: I'm not sure about the value, but also a good one ... there certainly are cosmic ray particles with energies of ~10²¹ eV, and while exceedingly rare, collisions of two such must happen. This would be like the LHC's quark-gluon plasma (on steroids ), but because we don't know what these EeV+ cosmic rays are, I doubt that we could estimate the equilibrium temperature in such a collision.

For those interested, I think it would be cool to explore the points ngc3314 made ... when you dump a humongous amount of energy into a (small) system, can you do it fast enough for the constituent particles to reach equilibrium (before they sap energy by pair production, say)?

[Strange]

For those interested, I think it would be cool to explore the points ngc3314 made ... when you dump a humongous amount of energy into a (small) system, can you do it fast enough for the constituent particles to reach equilibrium (before they sap energy by pair production, say)?

That is a good point. I think that is one reason the temperatures in accretion disks are relatively modest (on the scales being discussed here).

[Chuck]

I use characters like ∞ by copying and pasting them from wherever I can find them.

[Jean Tate]

I meant temperature as the temperature here is 20 C today, or the temperature of the star's photosphere is 9000 K, not the nerdy meaning that gives -200 K or plus infinity.

Here's a different take: instead of 'lead nucleus scale' things, what is the hottest temperature in the (post-SLS) universe, for macroscopic objects? Say ~1m, or ~1 au, or ~1 pc?

"Reach equilibrium" (or nearly so) would still apply.

Shocks, of various kinds, would be a good place to look, I think. How hot do the various shocks in various supernovae get?

Another probe: cosmic rays with EeV+ energies, and TeV (even PeV) gammas, certainly exist. Where are they created? In the places where they are born, are there macroscopic regions, more or less in equilibrium, with very high temperatures? My fave would be the engines which create the jets in AGNs - what are they? how hot do they get?

[Noclevername]

I meant temperature as the temperature here is 20 C today, or the temperature of the star's photosphere is 9000 K, not the nerdy meaning that gives -200 K or plus infinity.

Temperature of matter? Then, the last highest temp before the particles disassociate.