Super massive stars, black holes and galaxies

BoJangles · Dec 10, 2008

Super massive stars, black holes and galaxiesI had an interesting thought, though it probably has little substance. Could galaxies be the remnants of the first super massive stars or black holes that came into existence (light years across)?  Scattered all over the placeCould you get a star that big (I.e. light years across)? Is there way you could stop a star that big collapsing under its own weight? or whats the maxium theoretical limit a star can be.I wonder how much mass there is in the Milky Way, and how big a star would be that had so much mass.Or how big would a super massive black hole be if we feed it the Milky Way?Any got any thoughts on this?<edit>Since then ive found an article on SDChttp://www.space.com/scienceastronomy/050309_heavy_stars.htmlIt seems they are only finding them between 130 to 150 solar masssCould things have been a little diffrent 14 billion years ago? <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

Saiph · Dec 11, 2008

you should check your scale here.Galaxies are tens of thousands of light years across. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

BoJangles · Dec 11, 2008

Yeah it was a bit of a nonsense question

, though i kind of ment the resulting ball of matter, if you took the galaxies mass and put it in one place. <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

UFmbutler · Dec 11, 2008

I believe any star larger than about 100 solar masses would be so unstable it couldn't possibly exist.  At this mass the star is primarily supported by radiation pressure, which is inherently less stable than gas pressure.  Large stars are always very short-lived because of this - hence the large mass loss rates you see in supergiant stars. <div class="Discussion_UserSignature"> </div>

lildreamer · Dec 11, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Super massive stars, black holes and galaxiesI had an interesting thought, though it probably has little substance. Could galaxies be the remnants of the first super massive stars or black holes that came into existence (light years across)?  Scattered all over the placeCould you get a star that big (I.e. light years across)? Is there way you could stop a star that big collapsing under its own weight? or whats the maxium theoretical limit a star can be.I wonder how much mass there is in the Milky Way, and how big a star would be that had so much mass.Or how big would a super massive black hole be if we feed it the Milky Way?Any got any thoughts on this?<edit>Since then ive found an article on SDChttp://www.space.com/scienceastronomy/050309_heavy_stars.htmlIt seems they are only finding them between 130 to 150 solar masssCould things have been a little diffrent 14 billion years ago? Posted by Manwh0re</DIV> well according to good ol wiki largest stars are:http://en.wikipedia.org/wiki/VY_Canis_MajorisVy Canis Majoris is a red Hypergiant star located in Constellation of Canis Major. Tipping the scale at 1800 to 2100 solar radii. Its surface would extend to the orbit of Saturn. also from this articlehttp://www.universetoday.com/2008/04/06/what-is-the-biggest-star-in-the-universe/Roberta Humphreys from the University of Minnesota, the researcher who calculated the size of VY Canis Majoris, ..... She noted that the largest stars are the coolest. So even though Eta Carinae is the most luminous star we know of, it's extremely hot - 25,000 Kelvin - and so only a mere 400 solar radii.  The largest stars will be the cool supergiants. For example, VY Canis Majoris is only 3,500 Kelvin. A really big star would be even cooler. At 3,000 Kelvin, a cool supergiant would be 2,600 times the size of the Sun. T hat, she believes, is the largest possible star. But the current massive stars are HD 269810, Peony Nebula Star andPistol Star topping at 150 Solar Masses.http://en.wikipedia.org/wiki/List_of_most_massive_stars Black holes are the end point evolution of massive stars. Technically they are not stars, as they no longer generate nuclear fusion in their cores.<ul><li>Stellar black holes are objects with approx. 4–15 times the mass of our Sun. </li><li>Intermediate-mass black holes range from 100-10000 times the mass of our Sun. </li><li>Supermassive black holes are in the range of millions solar masses. </li></ul>Eddington's size limit<dl><dd><div class="noprint relarticle mainarticle">Main article: Eddington luminosity</div></dd></dl>Astronomers have long theorized that as a protostar grows to a size beyond 120 solar masses, something drastic must happen. Although the limit can be stretched for very early Population III stars, if any stars existed above 120 solar mass, they would challenge current theories of stellar evolution.The limit on mass arises because stars of greater mass have a higher rate of core energy generation, which is higher far out of proportion to their greater mass. For a sufficiently massive star, the outward pressure of radiant energy generated by nuclear fusion in the star’s core exceeds the inward pull of its own gravity. This is called the Eddington limit. Beyond this limit, a star ought to push itself apart, or at least shed enough mass to reduce its internal energy generation to a lower, maintainable rate. In theory, a more massive star could not hold itself together, because of the mass loss resulting from the outflow of stellar material.I apologize if my post seems confusing It really all boils down to the possiblity of a star even being 1 light year across is impossible. According to the articles I've read so far...IMO... <div class="Discussion_UserSignature"> </div>

BoJangles · Dec 12, 2008

Thanks that was a good read and i appreciate the links as well. <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

weeman · Dec 13, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>I believe any star larger than about 100 solar masses would be so unstable it couldn't possibly exist.  At this mass the star is primarily supported by radiation pressure, which is inherently less stable than gas pressure.  Large stars are always very short-lived because of this - hence the large mass loss rates you see in supergiant stars. Posted by UFmbutler</DIV> To add to that, it's also believed some of the first stars in the universe were so massive that they did indeed live very short lives, and died off in titanic supernovae. <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

DrRocket · Dec 13, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Super massive stars, black holes and galaxiesI had an interesting thought, though it probably has little substance. Could galaxies be the remnants of the first super massive stars or black holes that came into existence (light years across)?  Scattered all over the placeCould you get a star that big (I.e. light years across)? Is there way you could stop a star that big collapsing under its own weight? or whats the maxium theoretical limit a star can be.I wonder how much mass there is in the Milky Way, and how big a star would be that had so much mass.Or how big would a super massive black hole be if we feed it the Milky Way?Any got any thoughts on this?<edit>Since then ive found an article on SDChttp://www.space.com/scienceastronomy/050309_heavy_stars.htmlItseems they are only finding them between 130 to 150 solar masssCould things have been a little diffrent 14 billion years ago? Posted by Manwh0re</DIV>I am not an expert in stellar formation and physics, but it is my understanding that most of the elements in the current universe that are heavier than hydrogen and helium are the result of supernovae, so it would appear that much of the material in stars of the current era came from much older supernovae.  Since younger galaxies are composed of such stars you may be correct in some way.Black holes do not contribute matter, so, no, galaxies and stars are not remnants of black holes.  The area of the event horizon is proportional to the mass of a black hole, and therefore one could calculate the size of the event horizon of a black hole if you fed it the Milky Way,   I don't have that computation at hand, but you might try google. <div class="Discussion_UserSignature"> </div>

BoJangles · Dec 13, 2008

Hi guys, thanks for the replies.Hi I'm trying to work out the radius of the resulting ball of matter, if we could put all the mass of the Milky Way into a ball with the same density as our sun. * Define C             =3e8G             = 6.67e-11Sv           = Sun Volume    Sm          = 1.99e+30 kg                    Gm         = Galaxy Mass                                   Gv          = Galaxy Volume at Sol density                   = Sv * GmR             = Radius of the resulting ball of matter* Method Sv           = 1.41e+18 km3Gm         = 5.80e+11 MsolGv          = 8.19e+29 km3R             = {gv / ((4/3) *(pi))}(1/3) Km* Answer R             = 5.80e9 km ?<div style="padding-right:0cm;padding-left:0cm;padding-bottom:1pt;padding-top:0cm">That would be just outside of Neptune wouldn’t it? It doesn’t seem big enough; can anyone see any glaring errors?---</div>I suppose the Schwarzschild radius is what I'm looking for in regards to a black hole devouring the Milky WayRs = 2*(Gm*Sm)*G/c2Rs = 2*(5.80e+11*1.99e+30)*(6.67e-11)/(3e+8)2Rs = Now this just has to be wrong I must be messing up units somewhere, can anyone see where? <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

DrRocket · Dec 13, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Hi guys, thanks for the replies.Hi I'm trying to work out the radius of the resulting ball of matter, if we could put all the mass of the Milky Way into a ball with the same density as our sun. * Define C             =3e8G             = 6.67e-11Sv           = Sun Volume    Sm          = 1.99e+30 kg                    Gm         = Galaxy Mass                                   Gv          = Galaxy Volume at Sol density                   = Sv * GmR             = Radius of the resulting ball of matter* Method Sv           = 1.41e+18 km3Gm         = 5.80e+11 MsolGv          = 8.19e+29 km3R             = {gv / ((4/3) *(pi))}(1/3) Km* Answer R             = 5.80e9 km ?That would be just outside of Neptune wouldn’t it? It doesn’t seem big enough; can anyone see any glaring errors?---I suppose the Schwarzschild radius is what I'm looking for in regards to a black hole devouring the Milky WayRs = 2*(Gm*Sm)*G/c2Rs = 2*(5.80e+11*1.99e+30)*(6.67e-11)/(3e+8)2Rs = Now this just has to be wrong I must be messing up units somewhere, can anyone see where? Posted by Manwh0re</DIV>http://en.wikipedia.org/wiki/Schwarzschild_radiusYour calculation appears to be correct.  The values that you used for the various terms also checkout.  If you complete the calculation you would get Rs = 1.7*10^15 meters or about 0.18 light years.  I don't have a feel for this but, given that the diameter of the Milky Way Galaxy about 100,000 light years that does represent a significant compactification.  <div class="Discussion_UserSignature"> </div>

amaterasu · Dec 13, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Hi guys, thanks for the replies.Hi I'm trying to work out the radius of the resulting ball of matter, if we could put all the mass of the Milky Way into a ball with the same density as our sun. * Define C             =3e8G             = 6.67e-11Sv           = Sun Volume    Sm          = 1.99e+30 kg                    Gm         = Galaxy Mass                                   Gv          = Galaxy Volume at Sol density                   = Sv * GmR             = Radius of the resulting ball of matter* Method Sv           = 1.41e+18 km3Gm         = 5.80e+11 MsolGv          = 8.19e+29 km3R             = {gv / ((4/3) *(pi))}(1/3) Km* Answer R             = 5.80e9 km ?That would be just outside of Neptune wouldn’t it? It doesn’t seem big enough; can anyone see any glaring errors?---I suppose the Schwarzschild radius is what I'm looking for in regards to a black hole devouring the Milky WayRs = 2*(Gm*Sm)*G/c2Rs = 2*(5.80e+11*1.99e+30)*(6.67e-11)/(3e+8)2Rs = Now this just has to be wrong I must be messing up units somewhere, can anyone see where? Posted by Manwh0re</DIV> i seem to remember calculating the mass of the sun in high school physics classes using M=rv^2/G. where M = mass of the sun r = distance between the sun and the earth v = earth's orbital velocity G = gravitational constant, i.e. ca 6.7*10^-11  since it takes 1 year for the earth to orbit round the sun v = 2pi*r/1 year v = 2pi*1.5*10^8/365*24*60*60 v ~ 30.0 km/s now using M=rv~2/G M = 1.5*10^8*10^3*(30*10^3)^2/6.7*10^-11 M ~ 2.0*10^30kg we can combine the above with the fomula for the Schwarzschild radius r_s=2GM/c^2 r_s = 2*6.7*10^-11*2*10^30/(3*10^5*10^3)^2 r_s ~ 3.0*10^3 m r_s ~ 3km so, if there were to exist a black hole with the same mass as the sun, its radius would be about 3km. i dunno if that's what you wanted, though.  nevertheless, i hope it helps...  for now i've got to run.  cheers

BoJangles · Dec 14, 2008

Thanks DrRocket i appreciate your help and oversightAdditionally to amaterasu for the example    <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

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