Slashdot Mirror
Scientists Discover Teeny Tiny Black Hole
AbsoluteXyro writes "According to a Space.com article, NASA scientists have discovered the smallest known black hole to date. The object is known as 'XTE J1650-500'. Weighing in at a scant 3.8 solar masses and measuring only 15 miles across, this finding sheds new light on the lower limit of black hole sizes and the critical threshold at which a star will become a black hole upon its death, rather than a neutron star. XTE J1650-500 beats out the previous record holder, GRO 1655-40, by about 2.5 solar masses."
They say LHC-001 will be even smaller!
(But who will be there to measure...?)
Fears raised collider would create black holes that could swallow planet
HILARITY!
I see we weren't the first to build a large hadron collider.
It may look cute now. But they grow up.
While it may be possible that this black hole was formed from a relatively small (to form a black hole) star, couldn't it also be the case that it just a really old black hole? Hawkings told of how black holes can 'evaporate' over time with lack of surrounding matter, perhaps that could be the case here.
So, we've now discovered the biggest and smallest black holes known to exist within about a week of each other.
When we find the most average, space bears will come and blast us into porridge.
Astronomy kicks ass.
While black holes is not my area, I can tell you that when someone talks about the size of the black hole, they refer to the event horizon, since you can't really measure anything going on inside it.
The mass of the black hole is the most defining characteristic.
Violence is the last refuge of the incompetent. Polar Scope Align for iOS
They can't figure out the "critical threshold" because there isn't one. It all depends on too many variables to set a universal limit (hehehe get it...universal :-P) It depends on how much nuclear activity there is still going on when it start collapsing and what the amount of heavier atoms is and the amount of other things orbiting the star and any other forces affecting the star at that time and how fast it's moving and spinning. Mass is a smaller part of the calculation than they're making it sound like. If they're going to factor everything in just to find some minimum mass, well duh, two particles and a hell of a lot of force. Haven't they suggested that in that big particle accelerator aka donut of doom. So yeah, a critical mass threshold doesn't exist.
Google's Super Secret Search Algorithm: SELECT @search_results FROM internet WHERE @search_results = 'good'
A black hole, conventionally, consists of an event horizon surrounding a region of space from which you can't send information to the external world. This region of space is not a point, it has a well-defined circumference. (Because of the non-euclidean nature of general relativity, it doesn't actually have a well-defined radius (since you can't measure across the middle!) but people usually just consider the radius as if it were defined as the circumference divided by 2 pi, and don't worry about the fact that you can't actually measure it.)
At the center of the black hole is, according to general relativity, a point singularity, which indeed has no dimensions.
http://www.geoffreylandis.com
I believe they are referring to the diameter of the event horizon
Actually, that's only true of a non-rotating (or Kerr) singularity. All natural black holes will be rotating (the black hole maintains the rotational momentum of the pre-collapse mass). In a rotating black hole, the singularity is actually a ring (or torus). Inside that ring/torus, there is a tear in space.
It was this tear that lead, if I recall, to the original conjectures of a white hole, and the Einstein-Rosen bridge.
"Stumble before you crawl"
ok, I am ripping most of the info from here: http://www.physicsforums.com/showthread.php?t=122375&page=6
"If they were able to make a small blackhole, and it got "loose" and fell to the center of the Earth, the pressures at the Earths core would force material into it so fast that even a very small one would gobble us up very fast. I am not sure what the exact pressure is at the Earths core but it could force material through even a very small "hole" very quickly. I do agree that once it gobbled up the Earth, it would just continue to orbit the Sun, and the Moon would still orbit the blackhole as if it were the Earth..."
No, you should read this thread.
First of all, a black hole that falls to the center of the earth, wouldn't stop there, but would continue falling up on the other side, just to plunge in again, and on and on, because there's no "friction" on the black hole.
Second, there have been posted in this thread a lot of calculations of the speed at which it would gobble up matter.
Don't forget that the black hole we're talking about here IS MUCH MUCH SMALLER THAN A PROTON. As such, pressures on *atomic* level (such as in the center of the earth) matter little: the black hole travels most of the time in the empty space between nucleae.
A way to calculate the probability of hitting a nucleus (and somehow imagining that it would gobble up the entire nucleus, which is MUCH MUCH bigger than the black hole itself - which is a worst-case scenario) is done by calculating the "cross section" of the black hole and its probability to cross a nucleus on its voyages through the earth. We know its speed (just falling), and knowing the cross section and the density of nucleae, we can estimate how many nucleae it could eat per unit of time.
For a classical black hole, the calculation is done in the link provided by Pervect in this post:
http://www.physicsforums.com/showpos...4&postcount=12
for a MUCH LARGER black hole, about the size of a proton, weighting a billion tons (figure that! A black hole *the size of a proton* weights a billion tonnes ; we're talking here about black holes that weight 10 TeV or 10^(-24) kg - go figure how small it is !)
For more exotic calculations which are more severe, orion made some, and arrived at a time to eat the earth ~ 10^46 years.
All this in the following rather un-natural hypotheses:
- no Hawking radiation (which would make the black hole evaporate almost immediately)
- production of black hole EXACTLY IN THE CENTER OF GRAVITY of the collision (no remnant particles)
- very high production rate, producing billions of black holes per second.
I am not a physicist, but from what little physics I have had, and from reading threw the thread/flamewar, I dont think we have to worry about the LHC
Actually, the Schwarzchild solution does have a well-defined radius. In fact, the problem is that it has many well-defined radii, depending on what you mean by the term (as you point out, this comes about because of the non-Euclidean nature of the geometry). The commonly quoted "Schwarzschild radius" r = 2GM/c^2 is obtained by taking the area of the horizon and figuring out which "r" you would have to plug into A = 4 pi r^2 [true for a flat space sphere] to get the right result. Taking the circumference and dividing by 2 pi would achieve the same result. However, it is quite possible to figure out the proper distance between the horizon and the singularity by measuring the distance an infalling observer would travel. This distance is finite.
A problem can occur if you try and use constant time slices, using the "natural" time coordinate as defined by an observer far from the black hole. This gives silly results, but that is only because of badly behaved coordinates.
If that happens, what are we going to do!? Capitan Picard hasn't been born yet! Hell, even Kirk isn't around yet....
+1 IDisagreeSoHeMustBeATrollOrAnAstroturferOrAShill
This newly discovered Black Hole is the final result of a Large Hadron Collider, that caused a microsopic black hole on the third planet formerly circling the former star now known as 'XTE J1650-500'. So, this is not a naturally occuring black hole, but an alien-created one. Sadly this alien species is now extinct so they can't tell us how to avoid their mistake.
No, actually it doesn't. What is usually called the Schwartzschild "radius" is not actually a radius by the definition of the word, "distance to the center".
In fact, the problem is that it has many well-defined radii, depending on what you mean by the term (as you point out, this comes about because of the non-Euclidean nature of the geometry). The commonly quoted "Schwarzschild radius" r = 2GM/c^2 is obtained by taking the area of the horizon and figuring out which "r" you would have to plug into A = 4 pi r^2 [true for a flat space sphere] to get the right result.Exactly. You can calculate the area (which is well defined) and divide it by 4 pi, and you are free to call that the radius if you like. Or, equivalently, divide the circumference by two pi. But you can't measure the distance to the center.
Taking the circumference and dividing by 2 pi would achieve the same result. However, it is quite possible to figure out the proper distance between the horizon and the singularity by measuring the distance an infalling observer would travel. This distance is finite.Finite... and timelike. It would be a little like trying to define the radius of a circle if you're standing on the circumference, and the center is next Tuesday at noon.
A problem can occur if you try and use constant time slices, using the "natural" time coordinate as defined by an observer far from the black hole. This gives silly results, but that is only because of badly behaved coordinates.Within the event horizon, any choice of coordinates is rather badly behaved, because there is no well-behaved stationary coordinate system.
http://www.geoffreylandis.com
Well, maybe. Actually, rotating black holes radiate away angular momentum, and they also preferentially eat material that reduces their angular momentum, so it's an open question as to whether real black holes will be rotating. Probably, because the accretion disk is likely to be rotating, and it swallows up the accretion disk and gains the momentum from it, but I'm not sure you can necessarily say that all natural black holes will rotate.
In a rotating black hole, the singularity is actually a ring (or torus). Inside that ring/torus, there is a tear in space.It was this tear that lead, if I recall, to the original conjectures of a white hole, and the Einstein-Rosen bridge.
Actually, the Einstein-Rosen bridge comes from the maximum analytical extension of the Flamm embedding, way predating the Kerr solution. (It's a very trivial embedding, z = sqrt(r). The extension is z = plus or minus sqrt(r).) Turns out that the extended Flamm embedding is misleading, and a Schwartzschild black hole isn't a wormhole after all. But that wasn't obvious.
http://www.geoffreylandis.com
There are going to be a near-infinite number of quantum-scale black holes and wormholes in whatever volume of space you care to imagine. They evaporate almost instantly. As for stellar black holes, the Chandrasaker Limit is 2.5 solar masses, with a relatively small margin of error. Absolutely nothing of interest will be learned until we're within 2.75 solar masses, because then we can define sensible confidence limits on what the value actually is.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
as long as Stephen Hawking is still alive, I am sure he can handle it. After all Stephen Hawking beat all the other great scientists in poker with Commander Data in the far future, so he should be smarter than Picard or Kirk. If anyone knows how to reverse a black hole it would be Hawking.
Besides never apply a Star Trek solution to a Babylon Five problem.
Remember, Slashdot does not have a -1 disagree moderation, and no, troll, flamebait, and overrated are not substitutes.
for those wanting to find the article later, I strongly suggest Slashdot's own search instead of googling for the words "teeny", "tiny", "black" and "hole" :|