It's Official: Black Holes Have Lots Of Mass 70
KewlPC writes "Spaceflight Now reports in this article that some scientists have been able to measure the "weight" (yeah, yeah, it's actually mass, not weight) of a black hole that is (or was, 13 billion years ago) eating up the most distant known quasar, some 13 billion light years away."
Duh. (Score:5, Funny)
Re:Duh. (Score:1, Offtopic)
Re:Duh. (Score:1, Insightful)
Re:Duh. (Score:5, Funny)
Measurements show that 12% of the mass is single socks. Scientists are still trying to identify the other 88% of mass.
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Re:Duh. (Score:5, Funny)
Scientists have informally labeled the remaining 88% dark socks.
Re:Duh. (Score:2)
Re:Duh. (Score:2)
Neat (Score:5, Interesting)
The extreme brightness of this quasar also shows that the black hole in its core is swallowing matter at the maximum rate possible. This maximum rate is called the "Eddington Limit". If the black hole were accreting matter any faster, it would shine even brighter, and the intense luminosity would actually exert enough pressure to stop any more material falling in.
So there's a limit / "max throughput" to how much matter a black hole can suck in? Very interesting.
Re:Neat (Score:5, Informative)
But I haven't heard of the eddington limit before either. Neat.
Re: Neat (Score:3, Funny)
> So there's a limit / "max throughput" to how much matter a black hole can suck in? Very interesting.
Yep, there's bandwidth problems everywhere.
Re:Neat (Score:2)
Re:Neat (Score:2)
Max limit so mass of a star. (Score:1)
The above posts are correct that radiation pressure balances the force of gravity. But luminosity (the amount of radiation) goes up with mass way faster than gravity, so eventually the radiation pressure "wins" and the star gently blows apart. That provides an upper limit to normal stars. When I was taking stellar structure in grad school in the early 90's it was thought the limit is about 60 solar masses. Above
Re:Neat (Score:1)
not giving people much credit (Score:2, Funny)
interstellar dust does red shifting too (Score:2, Interesting)
interstellar dust reddens (Score:5, Informative)
Re:interstellar dust reddens (Score:1)
Re:interstellar dust reddens (Score:3, Informative)
Does this say anything about its size? (Score:3, Interesting)
I'm curious as to whether black holes are compacted so much that most of the space between atoms (and even subatomic particles?) is gone, or whether the repulsions keeping them apart are even stronger than the force of the black hole's gravity.
Now that they have a measure of the weight, if they know anything about the density or the size, they've got the other value as well.
Re:Does this say anything about its size? (Score:5, Informative)
Neutron stars are prevented from collapsing into black holes because of nuclear repulsion / neutron degeneracy (instead of electron repulsion). In fact, there's so much pressure that the electrons get squeezed into the protons of the atoms - hence neutron stars.
Black holes have enough gravity to overcome nuclear repulsion and collapse further than neutron stars. I think there's a couple theories about just what happens inside the black hole, but the commonality is that particles don't mean much whether or not you're talking about a singularity, or the non-singularity quantum foam theories.
Re:Does this say anything about its size? (Score:3, Informative)
Actually, the Schwarzschild radius of a black hole is proportionate to its mass. A black hole with mass the same as the Sun would have a 3 km radius; so just do the math if you want to find the radius of this one.
This page [berkeley.edu] has some good info.
Re:Does this say anything about its size? (Score:5, Informative)
I'm right in saying "the Schwarzschild radius of a black hole is proportionate to its mass", but more properly it's directly proportional; i.e., the proportionality constant is 1.
Well, as long as I'm here, let's do some calculations. The article says the black hole's mass is 3 billion times that of our Sun, so multiply 3 km by 3 billion and you get 3 km * 3*10^9 = 9 billion km. To put things in perspective: the distance to Alpha Centauri is 3.8*10^16 m = 3.8*10^15 km, so this black hole's radius is only .0002% of the distance from here to the nearest star. Quite small, astronomically-speaking.
I hope you got some sleep... (Score:3, Interesting)
Re:I hope you got some sleep... (Score:1)
Re:Does this say anything about its size? (Score:5, Interesting)
Something about that seems... counterintuitive?
You're saying that if I have a black hole with a mass of x, it has radius y. Then you say if it has mass 2x, it has radius 2y?
If a black hole is a sphere, doubling it's radius increases it's volume by a factor or about 33 1/2! Since mass only doubled, it's density just dropped by a factor of 17?
I admit I'm not very experienced with black holes, but if anything it seems a black hole would condense to some maximum possible density, and it would maintain that maximum possible density regardless of how much mass you add to it... so it just seems strange that doubling it's mass would actually double it's radius.
=Smidge=
Re:Does this say anything about its size? (Score:5, Interesting)
r0=2GM/c^2 (Eqn 10.1.5)
So it is directly proportional. However, I didn't look closely at the units that they are using here, but thta shouldn't matter to the solution at hand.
units (Score:2)
mks units (favored by many physicists):
G= 6.673x10^-11 N(m/kg)^2
cgs units (those wacky astronomers!):
G= 6.673x10^-7 dyne (cm/g)^2
Re:units (Score:1)
Re:Does this say anything about its size? (Score:3, Informative)
Correct. In your sphere example, a 2x mass increase will not yeld a 2x radius increase, since the relation between the two is not linear.
But a black hole is not a physical object, it's an abstraction. The radius of a blackhole is defined as the distance where the escape velocity equals lightspeed. And that distance is directly proportion
Re:Does this say anything about its size? (Score:1)
Thanks for the clarification.
=Smidge=
Re:Does this say anything about its size? (Score:2)
Once a star has collapsed into a black hole, you shouldn't use "radius" to describe it. Because of the way that space is curved inside a black hole, the distance from the central singularity to the event horizon is not a well-defined quantity (and is i
Re:Does this say anything about its size? (Score:3, Interesting)
At the least, you'd have to consider the black hole as a 2D surface (or shell). Which is still related to r^2.
Only speaking as a well read lay person,
Re:Does this say anything about its size? (Score:2)
Actually, no. From what I understand, the "size" of the black hole is actually the size of the event horizon, since the black hole itself has a size of zero and infinite density.
Re:Does this say anything about its size? (Score:2)
Actually, radius, circumference, and volume cease to have meaningful correlations in the vicinity of a macro relativistic object such as a black hole.
Density also is a meaningless measure when it comes to a black hole. Black holes are infinitely dense, since they have a measureable mass but their size is 0. A black hole is a point sour
Re:Does this say anything about its size? (Score:2)
WTF? Mass varies as the cube of the radius, so the radius must be multiplied by the cube root of 3 billion, which is about 1440. So the size of the black hole is about 4300 km.
Re:Does this say anything about its size? (Score:1)
Err, no. Volume varies as the cube of the radius. Mass at a constant density would as well, but then we're definately not talking about black holes, degenerate matter, or indeed any mass large enough to suffer compression under its own weight.
Re:Which size? (Score:2)
If you're talking about the physical size of the matter in the black hole, I don't know if that is something that can be measured. We'd have to find a way of getting data out out from below the event horizon. . .
Re:Does this say anything about its size? (Score:5, Informative)
Ok, first you get netron stars where the space between atoms is gone. The entire star becomes one big "nucleus". Then there are quark stars (I think they may still be uncertain about whether quark stars exist). In a quark star the space between subatomic particles (neutrons protons and electons) is gone.
THEN you get to black holes. Once you get within a certain distance of a black hole all laws of physics other than gravity effectively cease to exist. It isn't a question of gravity being stronger then the repulsion - the repulsion no longer exists. What happens is that the repulsive force itself gets pulled in by the gravity.
Think of it this way: Imagine the repulsive force is sound and gravity is wind. A black hole is where the wind is faster than the speed of sound. No matter how strong the repulsive sound is it gets carried inwards. It can't push outwards on anything.
We don't really understand what happens at this point. All known laws of physics break down within this region. We need to discover new laws of physics. The answer will probably be found in a theory of "Quantum gravity".
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Re:Does this say anything about its size? (Score:3, Informative)
The speed of sound in a medium is a function of the average velocity of the molecules in that medium. This is based off of the ideal-gas law, utilizing the probability of direction of particles bouncing off one another.. Collision of gas molecules against solidly compacted forces (such as the front-end of an ship (air/boat), an explosion wave-front, etc) merely causes the molecules to divert their direction, and such ping-ponging causes neighboring molecules to divert, the
Re:Does this say anything about its size? (Score:1, Informative)
We know both. Err... we know one and we know what general relativity predicts about the other, but we don't know how to merge that with quantum dynamics. The density of the black hole is infinite. Every bit of mass inside it is concentrated into a point of zero size - the singularity. So yes, all of the space between particles is gone. But of course being at such a small size, GR is outweighed by the quantum effects and we don't have a th
Re:Does this say anything about its size? (Score:1)
The use of the word "Inside" is interesting. The event horizon is a physical boundary of the rests of this Universe and what was that formed the black hole. So, outside is just equally appropriate, and equally meaningless (semantically, no offense).
BTW, text books say the "everything" are only mass and angular momentum. But if this is true, as "all the information of the matter fall onto the black hole will be lo
Re:Does this say anything about its size? (Score:1)
No? Enlighten me, please.
If a great battle is fought on a beach, but over time the arrowheads are ground into sand, the shafts rot away, and at some
Re:Does this say anything about its size? (Score:1)
Re:Does this say anything about its size? (Score:2)
You pose two excellent questions.
The physical size of a black hole depends on how you measure it and where you are and what you're doing when you measure it. The gravity near a black hole bends space itself in such a way that rulers contract and clocks run slower. Rulers only contract when in certain directions, and if a ruler is very close to the black hole those directions change randomly, continuously.
A direct consequence of this
eddington limit and black hole evaporation (Score:2, Interesting)
Given that in the process of evaporation, a black hole emits radiation, at some point the radiation pressure from the evaporation would balance out the force of gravity pulling matter into the black hole so then the black hole might stabilize in size.
Surely they'll have named that limit already, but I don't thin
Re:eddington limit and black hole evaporation (Score:5, Informative)
To put it another way, it's not a stable limit, it's an unstable limit. If a black hole is accreting mass at a rate less than or equal to this limit, the black hole will shrink and evaporate; if a black hole is accreting mass at a rate greater than the limit, it will grow.
Re:eddington limit and black hole evaporation (Score:1)
Re:eddington limit and black hole evaporation (Score:3, Interesting)
Re:eddington limit and black hole evaporation (Score:2)
Actually, very tiny blackholes can shrink. The radiation from a black hole is blackbody radiation resulting from the hole's "temperature", measured as the amount of chaos the matter that fell into the hole possessed.
As a hole gets smaller, that amount get
Re:eddington limit and black hole evaporation (Score:3, Interesting)
Besides, a black hole would have to swallow all the matter within its reach before it could shrink to the size necessary for the effect you describe to take place, because the more matter it takes in, the bigger it gets. And since it would have already taken in all the matter it can get ahold o
It limits accretion rate, not mass (Score:2)
Black hole evaporation is a slow process. It has essentially no effect on big black holes, and it isn't relevant t
Someone's bitter memories of high-school physics? (Score:5, Insightful)
What was all that about? Why not just say "the mass"? This is on a site that uses computer and physics jargon and acronyms all the time, mass isn't exactly an obscure concept.
Re:Someone's bitter memories of high-school physic (Score:2)
But you're right. I should've written mass and left it at that.
But how many silicon spheres is that? (Score:1)
Re:But how many silicon spheres is that? (Score:1)
Re:But how many silicon spheres is that? (Score:2)
And that, my friends, takes a lot of balls.
</I_Can_Not_Believe_I_Am_Responding_To_This>
&rimshot;
Black Holes Have Lots Of Mass... (Score:2, Funny)
Re:Black Holes Have Lots Of Mass... (Score:2)
yesterday news (Score:1)
What next? The weather forecast for the previous Big Bang?
Quick timeline question... (Score:2)
This timeline [pbs.org] gives the birth of stars at occuring roughly 1 billion years after the big bang, which this [space.com] article in January gives at between 11.2 and 20 billion years ago...
Wouldn't this hole place a lower limit of 14 billion years on the bang? And if last year's Hubble estimate of 13-14 billion years ago for the bang is right, wouldn't it pi
Nevermind... (Score:1)
-T
MgII (Score:1)