A Famous Black Hole Gets an Update
nytimes.com
A Famous Black Hole Gets an Update
1–10 of 11 posts
Re: A Famous Black Hole Gets an Update
#2This is undoubtedly a stupid question but I didn't see it covered by the article - this thing has been feeding on its neighbour for some time, is it inconceivable that it's now one or two solar masses larger than it was when it formed? Then it would have formed within the expected limit for new black holes (which I think is what they mean by the ~20Msol limit), but still be bigger today. What am I missing?
Re: A Famous Black Hole Gets an Update
#3This is undoubtedly a stupid question but I didn't see it covered by the article - this thing has been feeding on its neighbour for some time, is it inconceivable that it's now one or two solar masses larger than it was when it formed? Then it would have formed within the expected limit for new black holes (which I think is what they mean by the ~20Msol limit), but still be bigger today. What am I missing?
Yes, they would gain mass from feeding but not get 40% bigger while still in that binary configuration. So it seems these BHs start out bigger than previously assumed.
Re: A Famous Black Hole Gets an Update
#4This is undoubtedly a stupid question but I didn't see it covered by the article - this thing has been feeding on its neighbour for some time, is it inconceivable that it's now one or two solar masses larger than it was when it formed? Then it would have formed within the expected limit for new black holes (which I think is what they mean by the ~20Msol limit), but still be bigger today. What am I missing?
There are upper and lower limits for "stellar" black holes, the ones formed from stars. When some big stars die they form black holes, but the size of those resulting holes doesn't scale exactly with the size of the star. The really big stars will form a BH but will also eject most of their mass outwards. So there is an upper limit to the size of a BH formed from a star. This thing is bigger than that limit. It can grow by feeding off its binary but that doesn't account for all of its extra size. It could have merged with another BH, but its hard to see how that would have happened without destroying/ejecting the close binary star we still see today. Either something very very strange happened in the life of this BH (possible) or our models need to be refined (likely).
Re: A Famous Black Hole Gets an Update
#5This is undoubtedly a stupid question but I didn't see it covered by the article - this thing has been feeding on its neighbour for some time, is it inconceivable that it's now one or two solar masses larger than it was when it formed? Then it would have formed within the expected limit for new black holes (which I think is what they mean by the ~20Msol limit), but still be bigger today. What am I missing?
Yes, they would gain mass from feeding but not get 40% bigger while still in that binary configuration. So it seems these BHs start out bigger than previously assumed.
> Yes, they would gain mass from feeding but not get 40% bigger while still in that binary configuration
Why not? (also, one solar mass increase over twenty would be 5% larger wouldn't it?)
Re: A Famous Black Hole Gets an Update
#6This is undoubtedly a stupid question but I didn't see it covered by the article - this thing has been feeding on its neighbour for some time, is it inconceivable that it's now one or two solar masses larger than it was when it formed? Then it would have formed within the expected limit for new black holes (which I think is what they mean by the ~20Msol limit), but still be bigger today. What am I missing?
There are upper and lower limits for "stellar" black holes, the ones formed from stars. When some big stars die they form black holes, but the size of those resulting holes doesn't scale exactly with the size of the star. The really big stars will form a BH but will also eject most of their mass outwards. So there is an upper limit to the size of a BH formed from a star. This thing is bigger than that limit. It can g…
So do I take it that the twenty solar mass figure they were talking about in the article is not the (currently understood) upper limit to stellar black hole mass, but refers to something else?
The line I'm referring to is "...Astronomers know of a few dozen black hole X-ray binary systems in the Milky Way and nearby, all of which have imputed masses of less than 20 times that of the sun. That apparent limit suggested that it was hard for black holes to grow more massive..."
Re: A Famous Black Hole Gets an Update
#7Earlier quoted context omitted.
There are upper and lower limits for "stellar" black holes, the ones formed from stars. When some big stars die they form black holes, but the size of those resulting holes doesn't scale exactly with the size of the star. The really big stars will form a BH but will also eject most of their mass outwards. So there is an upper limit to the size of a BH formed from a star. This thing is bigger than that limit. It can g…
So do I take it that the twenty solar mass figure they were talking about in the article is not the (currently understood) upper limit to stellar black hole mass, but refers to something else? The line I'm referring to is "...Astronomers know of a few dozen black hole X-ray binary systems in the Milky Way and nearby, all of which have imputed masses of less than 20 times that of the sun. That apparent limit suggested…
There is a theoretical mass gap based on mathematical models of how stars work. Then there is a mass gap based on observations of real BHs. These gaps don't line up perfectly. Either our observations are imperfect or our math is wrong.
Re: A Famous Black Hole Gets an Update
#8Earlier quoted context omitted.
So do I take it that the twenty solar mass figure they were talking about in the article is not the (currently understood) upper limit to stellar black hole mass, but refers to something else? The line I'm referring to is "...Astronomers know of a few dozen black hole X-ray binary systems in the Milky Way and nearby, all of which have imputed masses of less than 20 times that of the sun. That apparent limit suggested…
There is a theoretical mass gap based on mathematical models of how stars work. Then there is a mass gap based on observations of real BHs. These gaps don't line up perfectly. Either our observations are imperfect or our math is wrong.
Thanks for your answers so far, I'm sorry I'm still being dim - the 'mass gaps' per the Wikipedia article you linked are thought to be in the region of "2 to 5 and 50 to 150 solar masses", and therefore stellar black holes are expected to be around 5-50 solar masses. The NYT article puts Cygnus X1 at 21 solar masses and therefore safely in the realm of possibility, but apparently now big enough to cause a problem, being bigger than 20 solar masses which was some other previous limit (the limit for a binary system?). I don't understand why it couldn't have been <= 20Msol at formation, and then acquired the rest parasitically from it's companion.
Re: A Famous Black Hole Gets an Update
#9Earlier quoted context omitted.
Yes, they would gain mass from feeding but not get 40% bigger while still in that binary configuration. So it seems these BHs start out bigger than previously assumed.
> Yes, they would gain mass from feeding but not get 40% bigger while still in that binary configuration Why not? (also, one solar mass increase over twenty would be 5% larger wouldn't it?)
Because anything that massive getting into a binary system will certainly destabilise it.
Re: A Famous Black Hole Gets an Update
#10Earlier quoted context omitted.
Yes, they would gain mass from feeding but not get 40% bigger while still in that binary configuration. So it seems these BHs start out bigger than previously assumed.
> Yes, they would gain mass from feeding but not get 40% bigger while still in that binary configuration Why not? (also, one solar mass increase over twenty would be 5% larger wouldn't it?)
There are some complex dynamics that take place when mass transfer is happening. In these systems this is via Roche Lobe overflow (1) which depending on the masses of the objects can become unstable after a large mass transfer. But going back to your original point, I guess there may be some configuration that leads to what to you are suggesting. Might be an interesting thing to model to see if it is possible!