# Are there any limits to Star Size? **URL:** \ **Category:** Factual Questions\ **Created:** [April 24, 2015, 5:17pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453 "2015-04-24T17:17:48Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![AK84](https://avatars.discourse-cdn.com/v4/letter/a/85e7bf/32.png) [@AK84](https://boards.straightdope.com/u/AK84)\ **Post date:** [April 24, 2015, 5:17pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/1 "2015-04-24T17:17:48Z")
Is there any limit to the maximum size a star can get, even mathematically worked out? By Mass? Volume? Radius? ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [April 24, 2015, 5:59pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/2 "2015-04-24T17:59:03Z")
Apparently, there does seem to be a [size limit](http://www.space.com/858-study-stars-size-limit.html) of about 150 solar masses. The limit seems to be based, though, on empirical evidence, rather than theoretical. Large stars burn their nuclear fuel more quickly, so are more difficult to locate. ---
**Author:** ![Tapioca\_Dextrin](https://avatars.discourse-cdn.com/v4/letter/t/3d9bf3/32.png) [@Tapioca\_Dextrin](https://boards.straightdope.com/u/Tapioca_Dextrin)\ **Post date:** [April 24, 2015, 6:01pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/3 "2015-04-24T18:01:50Z")
The romantically named [R136a1](https://en.wikipedia.org/wiki/R136a1) is the most massive star, weighing in at ~265 time the mass of the Sun The biggest star we know of is [VY Canis Majoris](https://en.wikipedia.org/wiki/VY_Canis_Majoris) which is in the ballpark of 1,400 the diameter of the Sun (bigger than orbit of Jupiter) The limiting factor is the [Eddington Limit](https://en.wikipedia.org/wiki/Eddington_luminosity). Go beyond that and the star tears itself apart pretty rapidly. ---
**Author:** ![AK84](https://avatars.discourse-cdn.com/v4/letter/a/85e7bf/32.png) [@AK84](https://boards.straightdope.com/u/AK84)\ **Post date:** [April 24, 2015, 6:21pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/4 "2015-04-24T18:21:15Z")
Stars AFAIK are in an equilibrium between the inward forces of gravity and the outward forces of the nuclear fusion. If you increase the mass, there is now more fusion in the coire which supplies more outward pressure and counteracts the gravity. Can the mass be increased _ad infinitum_ then? ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [April 24, 2015, 6:34pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/5 "2015-04-24T18:34:26Z")
Really massive stars tend to have very strong stellar winds, which blow material off of them. Another problem is, our current models of star formation say you should only be able to get stars up to about 150 times the mass of the Sun through normal star formation mechanisms. One theory to explain larger stars is that they result from stellar collisions. This theory also explains [blue stragglers](http://en.wikipedia.org/wiki/Blue_straggler) in globular clusters. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [April 24, 2015, 6:39pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/6 "2015-04-24T18:39:10Z")
> [@AK84](#): > > Stars AFAIK are in an equilibrium between the inward forces of gravity and the outward forces of the nuclear fusion. If you increase the mass, there is now more fusion in the coire which supplies more outward pressure and counteracts the gravity. Can the mass be increased _ad infinitum_ then? Increase the mass enough and you get a black hole. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 24, 2015, 8:38pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/7 "2015-04-24T20:38:43Z")
> [@Lemur866](#): > > Increase the mass enough and you get a black hole. Nope: It’s density not mass that defines a black hole. You could theoretically have a black hole with the mass of the Earth (but it won’t last long). Adding more mass to a star just gives you a bigger, less stable star. The previously posted data gives a hint at to the issues facing Astrophysicists in determing the maximum mass of a star. There’s just too many variables and not enough data to really get a hard limit. It also depends on your definition of “star”. If you have a good size neutron star that collides with a supermassive star and is resuming fusion for a brief while, is that a “star” in the same since as Sol and Betelguese? How much strange matter can you throw in and not be cheating? ---
**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:** [April 24, 2015, 9:02pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/8 "2015-04-24T21:02:14Z")
It’s neither density nor mass that defines a black hole. It’s the ratio of mass to radius. This means that, for instance, a supermassive black hole can have a density as low as that of water or even of air. It also means that, for any given density, there’s an upper size limit before you become a black hole. The limit kicks in even faster if the density increases as the size increases. ---
**Author:** ![DrCube](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@DrCube](https://boards.straightdope.com/u/DrCube)\ **Post date:** [April 24, 2015, 9:04pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/9 "2015-04-24T21:04:38Z")
> [@ftg](#): > > Nope: It’s density not mass that defines a black hole. You could theoretically have a black hole with the mass of the Earth (but it won’t last long). This is true, but it ignores the fact that the life cycle of stars depend on their mass. Stars above a certain size all end up as black holes eventually, while stars below that size never will. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [April 25, 2015, 2:41am UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/10 "2015-04-25T02:41:42Z")
> [@ftg](#): > > Nope: It’s density not mass that defines a black hole. You could theoretically have a black hole with the mass of the Earth (but it won’t last long). For some value of “won’t last long”. A black hole with a mass of 10[sup]11[/sup] kg would have a lifetime about equal to the current age of the universe. From the equation [here](http://http://physicspages.com/2013/12/10/black-hole-evaporation-how-long-will-a-black-hole-live/), that gives a lifetime of order 10[sup]50[/sup] years for an Earth mass black hole. When 10[sup]50[/sup] years old you reach, look as good you will not. ---
**Author:** ![Novelty\_Bobble](https://avatars.discourse-cdn.com/v4/letter/n/a3d4f5/32.png) [@Novelty\_Bobble](https://boards.straightdope.com/u/Novelty_Bobble)\ **Post date:** [April 25, 2015, 12:38pm UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/11 "2015-04-25T12:38:17Z")
> [@Anne\_Neville](#): > > This theory also explains [**blue stragglers**](http://en.wikipedia.org/wiki/Blue_straggler) in globular clusters. Ooooo! thanks for the heads-up on both a cosmic phenomenon new to me and a stunning band name. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [April 27, 2015, 3:01am UTC](https://boards.straightdope.com/t/are-there-any-limits-to-star-size/718453/12 "2015-04-27T03:01:23Z")
If you can’t form stars of greater than, say, 150 solar masses except through collisions with other stars, that might give you a limit, at least for practical purposes. Stellar collisions are rare outside of very dense environments like the central part of a globular cluster or galaxy. You might get a few larger stars that resulted from one collision, but far fewer that resulted from two collisions. You don’t have a lot of time for a second collision to happen (on stellar timescales, at least), since more massive stars have shorter lives than less massive ones.