# Black holes: does fusion continue and no heat escape? **URL:** \ **Category:** Factual Questions\ **Created:** [March 14, 2013, 5:45pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934 "2013-03-14T17:45:33Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![The\_Second\_Stone](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@The\_Second\_Stone](https://boards.straightdope.com/u/The_Second_Stone)\ **Post date:** [March 14, 2013, 5:45pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/1 "2013-03-14T17:45:33Z")
The title says it all. Presumably heat cannot escape. These seems to violate the laws of thermodynamics, but I gather grabity trumps thermodynamics. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [March 14, 2013, 6:07pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/2 "2013-03-14T18:07:00Z")
> [@The\_Second\_Stone](#): > > The title says it all. Presumably heat cannot escape. These seems to violate the laws of thermodynamics, but I gather grabity trumps thermodynamics. Black hole thermodynamics is a topic in it’s own right. Basically in the classical theory (general relativity) black holes don’t obey thermodynamics, however once you introduce quantum theory in a semiclassical regime you find black holes can give off heat in the form of Hawking radiation. ---
**Author:** ![The\_Second\_Stone](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@The\_Second\_Stone](https://boards.straightdope.com/u/The_Second_Stone)\ **Post date:** [March 14, 2013, 6:10pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/3 "2013-03-14T18:10:28Z")
I’m not talking tiny, itty bitty amounts, but rather, does a solar system where the star has gone black holey, feel real cold? ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [March 14, 2013, 7:12pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/4 "2013-03-14T19:12:40Z")
No more nuclei, no more fusion. Only mass. No size, no distance, only mass. No neutrons, only mass. ---
**Author:** ![FuzzyOgre](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@FuzzyOgre](https://boards.straightdope.com/u/FuzzyOgre)\ **Post date:** [March 14, 2013, 7:16pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/5 "2013-03-14T19:16:35Z")
> [@Napier](#): > > No more nuclei, no more fusion. Only mass. No size, no distance, only mass. No neutrons, only mass. Sorta like Catholicism on Easter Friday. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [March 14, 2013, 7:24pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/6 "2013-03-14T19:24:01Z")
> [@The\_Second\_Stone](#): > > I’m not talking tiny, itty bitty amounts, but rather, does a solar system where the star has gone black holey, feel real cold? I don’t think it’s possible for a star in a solar system to turn into a black hole. The black holes we think we’ve found are the massive ones at the centers of galaxies, the size of millions of stars. Those have immense amounts of gravity and any planets would have been destroyed long ago. The area surrounding them is visible in a variety of wavelengths because the gases falling into the black hole are accelerated. Are you asking a theoretical question about the sun magically turning into something it can’t or a question about real-world black holes or something else? ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [March 14, 2013, 7:28pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/7 "2013-03-14T19:28:37Z")
> [@The\_Second\_Stone](#): > > I’m not talking tiny, itty bitty amounts, but rather, does a solar system where the star has gone black holey, feel real cold? It’s not likely that a solar system would survive the star turning into a black hole - it’s generally a pretty violent process. But, yes, it would be quite cold around the black hole because virtually nothing would be emitted. A black hole with an accretion disk (matter fall into it) might give off a substantial amount of energy as the components in the disk heat up - we often pick up black holes because of X-rays emitted by the accretion disk. Going back to the original question, though… there would be no fusion inside the black hole because you don’t have protons - or any other kind of mass that we see elsewhere. Whatever does happen inside, fusion is definitely not included. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [March 14, 2013, 7:52pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/8 "2013-03-14T19:52:23Z")
> [@dracoi](#): > > Going back to the original question, though… there would be no fusion inside the black hole because you don’t have protons - or any other kind of mass that we see elsewhere. Whatever does happen inside, fusion is definitely not included. Is this true? The black hole is not the same as the singularity, I don’t believe matter is instantly destroyed once it crosses the event horizon. In fact black holes can display a charge, I thought, so some of the electron-ness or quark-ness must survive the passage, Id think. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [March 14, 2013, 8:00pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/9 "2013-03-14T20:00:01Z")
> [@Exapno\_Mapcase](#): > > I don’t think it’s possible for a star in a solar system to turn into a black hole. The black holes we think we’ve found are the massive ones at the centers of galaxies, the size of millions of stars. Not true. The first black hole we identified was a binary in a normal-ish solar system: [Cygnus X-1](http://en.wikipedia.org/wiki/Cygnus_X-1). Stephen Hawking bet it wasn’t one and conceded the bet sometime in the 90s after we got better data. There’s some question as to the exact mass required for black hole formation (the Chandrashekar limit), but we know massive stars can absolutely become black holes. ID’ing them isn’t easy, but there are several candidates much closer than the galactic center. Here’s a [list](http://en.wikipedia.org/wiki/Stellar_black_hole) per wiki. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [March 14, 2013, 8:20pm UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/10 "2013-03-14T20:20:20Z")
Yes black holes are very cold objects and within a fairly short space of time a collapsing object will settle down to one that can be described by only a small set of parameters (therefore it must losee most of it’s former properties) One feasible method of black hole formation is by the stellar evaporation-induced collapse of dense clusters of stars. Presumably many of the planets orbiting the stars would also contribute to the mass of the resulting supermassive black hole. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [March 15, 2013, 12:26am UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/11 "2013-03-15T00:26:40Z")
> [@Great\_Antibob](#): > > Not true. The first black hole we identified was a binary in a normal-ish solar system: [Cygnus X-1](http://en.wikipedia.org/wiki/Cygnus_X-1). Stephen Hawking bet it wasn’t one and conceded the bet sometime in the 90s after we got better data. > > There’s some question as to the exact mass required for black hole formation (the Chandrashekar limit), but we know massive stars can absolutely become black holes. > > ID’ing them isn’t easy, but there are several candidates much closer than the galactic center. Here’s a [list](http://en.wikipedia.org/wiki/Stellar_black_hole) per wiki. I’m going to defend myself because I chose my words carefully. I wrote that “a star in a solar system” can’t turn into a black hole. From your link, the star that was the progenitor of Cygnus X-1 weighed about 40 solar masses. Such hyper stars are unstable, give off massive radiation, and are apparently much too short lived to spawn solar systems. Stars might be able to become black holes, but not stars in solar systems. If I’m wrong about that, I’ll accept correction, but until then my original statement still stands. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [March 15, 2013, 12:58am UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/12 "2013-03-15T00:58:53Z")
> [@The\_Second\_Stone](#): > > The title says it all. Presumably heat cannot escape. These seems to violate the laws of thermodynamics, but I gather grabity trumps thermodynamics. One could argue that grabity would have been a better name for it all along. 🙂 ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [March 15, 2013, 1:00am UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/13 "2013-03-15T01:00:51Z")
> [@Exapno Mapcase](#): > > Stars might be able to become black holes, but not stars in solar systems. If I’m wrong about that, I’ll accept correction, but until then my original statement still stands. Interesting. The Wikipedia list of extrasolar host stars has by my count only 10\* out of 678 planetary host stars with a mass of over 2 solar masses, with the most massive at 2.7. None of those would be massive enough to form a black hole. - My eyes were glazing over after scrolling through that list, so this number should be considered only approximate. ---
**Author:** ![Folly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/folly/32/3219_2.png) [@Folly](https://boards.straightdope.com/u/Folly)\ **Post date:** [March 15, 2013, 2:11am UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/14 "2013-03-15T02:11:56Z")
> [@Great\_Antibob](#): > > Stephen Hawking bet it wasn’t one and conceded the bet sometime in the 90s after we got better data. Has poor Mr. Hawking won _any_ of his famous wagers? I think he just likes playing devil’s advocate. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 15, 2013, 4:25am UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/15 "2013-03-15T04:25:47Z")
They’re not Hawking’s famous wagers, so much as Kip Thorne’s famous wagers. So far, Kip’s track record is that he’s lost every wager that involved human action, and won every one that didn’t. For the Cyg X1 wager specifically, Hawking expected to lose: He made the bet as a sort of insurance policy, because he’d invested a lot of his career in the existence of black holes. > [@](#): > > Quoth **OldGuy** : > Is this true? The black hole is not the same as the singularity, I don’t believe matter is instantly destroyed once it crosses the event horizon. In fact black holes can display a charge, I thought, so some of the electron-ness or quark-ness must survive the passage, Id think. Crossing the event horizon is not in itself instant destruction, but it does mean that you’ll inevitably reach the singularity eventually, and “eventually” in this case is generally a very short time. And the singularity does mean absolute instant destruction. Black holes _can_ have charge, but that’s one of only a very small number of properties they can have: They cannot, for instance, have lepton number or baryon number. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [March 15, 2013, 6:43am UTC](https://boards.straightdope.com/t/black-holes-does-fusion-continue-and-no-heat-escape/652934/16 "2013-03-15T06:43:37Z")
> [@Exapno\_Mapcase](#): > > I don’t think it’s possible for a star in a solar system to turn into a black hole. The black holes we think we’ve found are the massive ones at the centers of galaxies, the size of millions of stars. The [smallest one](http://en.wikipedia.org/wiki/GRO_J0422%2B32) we’ve found so far is thought to have a mass of about four solar masses; the limit of black hole formation is thought to be around three. While we haven’t found a star of (quite, as **ZenBeam** shows) that mass with planets, that’s likely an artefact of our detection methods; in fact, it’s thought that planet formation is harder around lower mass stars.