What is the biggest Star in the known Universe....

[Spaceman500]

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[a_lost_packet_]

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Well, for a "star" that might be Canis Majoris as far as we can tell. It obvious that as far as the "Universe" goes, there could be other, larger ones out there we don't know about.

Universe Today: What is the biggest star in the Universe?



That's... pretty darn big.

 

[ramparts]

Yep - the real trick in answering that question is that stars, even really really big ones, just aren't that bright, so the biggest ones we know of are all going to be within our galaxy, and not very far away within the galaxy either. Even enormous stars on the other side of the galaxy or in the center or some other obscured region are likely to escape our notice. So there's certainly tons of bigger stars than the one in the post above - that just happens to be the biggest one we've been lucky enough to find

The other problem with knowing what the biggest star is is that both measures of ¨bigness¨ - mass and radius - are extremely difficult to measure observationally, so we can really only use best guesses.

 

[nimbus]

[youtube]http://www.youtube.com/watch?v=HEheh1BH34Q[/youtube]

 

[ZenGalacticore]

Nimbus- Awesome vid! I'm surprised that clip wasn't incorporated into "The Universe", one of the few shows on the History Channel that I like; or on "Journey Through the Universe" on Nat Geo.

And the size of the Pacific Ocean is barely comprehensible to us. When looking at pics of Earth from high orbit, I often try to picture ten Earths, lined up in a row off into the distance to get an idea of the diameter and size of Jupiter. Then picturing ten Jupiters lined up to get an idea of the diameter and size of the Sun.

And the Sun is a relatively puny star. What a trip!

 

[Couerl]

Put another way; What is the largest in terms of size and mass that a star can become? I imagine there is a known or at least inferred limit where anything larger will simply collapse in to a BH. Stars get their size by two competing forces, gravity crushing the mass to a central point and fusion exploding the mass outward against its own gravity. The balance of these forces and the makeup of the star including mass will determine its size. Since CM is the largest star we have observed it seems safe to me to suppose that they cannot physically get much bigger..

 

[MeteorWayne]

According to our latest understanding, that's not true. The first stars, without the cooling effects of metals (elements heavier than He) may have been many times bigger. Of course, they are long gone and we can't observe them...

 

[ZenGalacticore]

According to our latest understanding, that's not true. The first stars, without the cooling effects of metals (elements heavier than He) may have been many times bigger. Of course, they are long gone and we can't observe them...

And it is my understanding that these primordial 'superstars' were relatively short-lived. Only ten or 100 million years, perhaps? Before they went supernova kablewy and set the stage for the second generation of "regular" stars.

 

[nimbus]

And the Sun is a relatively puny star. What a trip!

It's mind-boggling. If only we could see these all in person. And these are only a fraction of all those in our one galaxy.

 

[ramparts]

According to our latest understanding, that's not true. The first stars, without the cooling effects of metals (elements heavier than He) may have been many times bigger. Of course, they are long gone and we can't observe them...

And it is my understanding that these primordial 'superstars' were relatively short-lived. Only ten or 100 million years, perhaps? Before they went supernova kablewy and set the stage for the second generation of "regular" stars.

If that. A star's mass is inversely proportional to its lifetime, so these stars were by far the shortest-lived in the Universe's history. And it's a good thing for us, too - the quicker they get out their heavy elements, the quicker we get to form!

 

[CalliArcale]

One other thing to remember is that although the video depicted the stars as spheres, they really can be quite irregular. The larger stars are quite diffuse in their outer layers. (And diameter isn't just a function of mass. It is also a function of the phase of nuclear fusion. Our Sun will be much larger when it becomes a red giant, but it will also have lost a great deal of mass, so it will be *less* massive when it is bigger.) Because they are so diffuse, it's easy for them to become distorted. Rotation can make the star flatten out (and several examples of this have been found), and mind-bogglingly gigantic bubbles of hot plasma can form, causing the star to bulge out in places. Betelgeuse has been seen to change size and shape fairly significantly; it's big enough and close enough that its shape can be directly observed, though the resolution is poor even with really freakin' huge telescopes. Complicating things further is that they are so diffuse that the boundary between "star" and "space" is difficult to determine. They don't really have an edge; they just sort of fade out along the edges.

 

[gypstar]

damn thats huge

 

[Couerl]

According to our latest understanding, that's not true. The first stars, without the cooling effects of metals (elements heavier than He) may have been many times bigger. Of course, they are long gone and we can't observe them...

Hi Wayne and thanks for bringing this up, it reminds me of something else I saw recently on one of those space shows, but first: ya sure, the original stars were bigger, makes perfect sense, but still doesn't negate the idea that there is/was/always has been a theoretical if not actual weight limit to a star. I don't know what it is or would be, but it seems likely at least on an intuitive level.

As far as metals and such go, I had heard on a program recently (How the universe works or something like that) that once a red giant begins to fuse iron that it would go super nova within 1 second, because the core could no longer support fusion enabling it to counter its own gravity etc. The visual they gave seemed odd to me because there is so much iron out there (around here anyway) and I wondered if that was accurate. Couldn't a red giant fuse iron for years until the core was so large/dense that it could then no longer support fusion? I'm unclear on this and need to study up some.

 

[MeteorWayne]

Well, the understanding that metals were involved in cooling, hence creating "normal" stars is IIRC, only a few decades old, so the concept of stars without such an effect is just being examined.

Re the iron thing, that is what I had always understood (a few seconds) but Stephen Hawking's Universe tonight suggested it's a longer process...years long...which I don't think is correct, but I'll have to do more research myself.

MW

 

[eburacum45]

One other thing to remember is that although the video depicted the stars as spheres, they really can be quite irregular. The larger stars are quite diffuse in their outer layers. (And diameter isn't just a function of mass. It is also a function of the phase of nuclear fusion. Our Sun will be much larger when it becomes a red giant, but it will also have lost a great deal of mass, so it will be *less* massive when it is bigger.) Because they are so diffuse, it's easy for them to become distorted. Rotation can make the star flatten out (and several examples of this have been found), and mind-bogglingly gigantic bubbles of hot plasma can form, causing the star to bulge out in places. Betelgeuse has been seen to change size and shape fairly significantly; it's big enough and close enough that its shape can be directly observed, though the resolution is poor even with really freakin' huge telescopes. Complicating things further is that they are so diffuse that the boundary between "star" and "space" is difficult to determine. They don't really have an edge; they just sort of fade out along the edges.

You might be interested in a model of Betelgeuse I've made recently

here it is on youtube
http://www.youtube.com/watch?v=hZg1bNG-DS0

 

[nimbus]

So it's really that globular? The irregularities of its shape aren't just massive flares?

 

[eburacum45]

Well, here is a page of movies which show numerical simulations of the surface of a red supergiant.
http://www.astro.uu.se/~bf/movie/dst35g ... movie.html
and more here
http://www.astro.uu.se/~bf/movie/movie.html
As you can see the simulations are very irregular.

Freytag has shown the surface of his simulated stars as a deep red, but it appears thar Betelgeuse is hotter than that- closer to the temperature of an incandescent light-bulb.

 

[nimbus]

Very cool, thanks!

 

[starialove]

WE ALL KNOW THAT THE SUN ISNT THE BIGGEST STAR IN THE UNIVERSE :roll:

 

[MeteorWayne]

No one said it is.

 

[darkmatter4brains]

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Well, for a "star" that might be Canis Majoris as far as we can tell.



That's... pretty darn big.

This image boggles my mind EVERY time I see it :shock:

 

[neuvik]

Whoa, everybody is going on the super red giant trip. The OP didn't define big, so I dont think we should be limited to some uninpresive diameter for the winner.

I submit R136a1! This star has 250 solar masses to its credit, compared to VY Canis Majors which is like 20... R136a1 is the heavy weight, and would tear any of those wimpy super red giant to pieces.

Also discussed here: viewtopic.php?f=12&t=25325

 

[Couerl]

I submit R136a1! This star has 250 solar masses to its credit, compared to VY Canis Majors which is like 20... R136a1 is the heavy weight, and would tear any of those wimpy super red giant to pieces.

Also discussed here: viewtopic.php?f=12&t=25325

250? Sure about that? From my understanding anything around and over 40 solar masses is going to collapse (BH) because no amount of fusion can sustain it. I don't think we have an absolute known limit, but I forsee one being pegged in the not too distant future..

 

[neuvik]

250? Sure about that? From my understanding anything around and over 40 solar masses is going to collapse (BH) because no amount of fusion can sustain it. I don't think we have an absolute known limit, but I forsee one being pegged in the not too distant future..

Yea I'm sure. Do you have any supporting evidence that if a star gets to 40 solar masses it immediatly becomes a black hole? The massive stars that formed after the radiation era where many times larger than anything we have seen...composed simply of hydrogen and helium as one member already wrote. The only problem with massive stars (as already written) is that they have intensly short lifespan. But that in its self is not a true limit to the mass a star can achieve.

On a side note, the VLT was monitering a supernova that should have resulted in a black hole that instead has seemed to produce a highly magnetic neutron star. http://www.astronomynow.com/news/n1008/20magnetar/

 

[Saiph]

stars can easily mass over 40 solar masses, as long as the fusion is going it can support it. Previous limits were at ~200 solar masses, and that limit wasn't because of an inability to support the weight, but our understanding of the process of a star growing to that size meant that it would blow off even the densest gas cloud before it could accrue enough mass to get much larger than that.

Finding a star bigger than that, has required astronomers to go back and look at special cases and unusual possibilities to see how it managed it.


Stars over 40 solar masses, once the core fusion ends, will collapse into a BH though.