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Largest Black Hole Measured

kdawson posted more than 6 years ago | from the that's-no-moon dept.

Space 170

porkpickle tips us to a BBC article on the quasar OJ287, a binary object containing largest black hole yet discovered, weighing in at 18 billion times the mass of Sol. Researchers were able to estimate its mass due to the presence of a smaller black hole in orbit around it. When the smaller companion's orbit intersects OJ287's accretion disk, once every 12 years, it triggers a burst of radiation that was detected by the Spitzer Space Telescope. More detail and a diagram are available on the Turku University site.

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eh? I don't get it? (4, Interesting)

Anonymous Coward | more than 6 years ago | (#22000620)

How large can a singularity be?

I mean, if they used the word "massive" I'd get it. But large?

Re:eh? I don't get it? (4, Informative)

AmaDaden (794446) | more than 6 years ago | (#22000948)

It think they are not 100% sure about the whole "a black hole is a singularity" thing.

quantum mechanics .... does not allow objects to have zero size--so quantum mechanics says the center of a black hole is not a singularity but just a very large mass compressed into the smallest possible volume.
from http://en.wikipedia.org/wiki/Black_hole [wikipedia.org]

Re:eh? I don't get it? (5, Informative)

BobGod8 (1123841) | more than 6 years ago | (#22002262)

Actually it's way more complicated than that. Only non-rotating black holes could ever truly be point masses. Any angular momentum creates complicated tidal effects near the center, resulting in a non-point-mass. Carried further, the "singularity" expands until the point where it would effectively reach the event horizon itself, resulting in a naked singularity, which some calculations have shown can have actual size. Adding further rotation will (to a point), actually change the size of the "singularity". Of course, this is all moot, since that's not at all what the article was talking about, but that's my .02$.

Re:eh? I don't get it? (5, Informative)

Anonymous Coward | more than 6 years ago | (#22003696)

That's misleading, and I'm guessing you don't really understand what you're describing. A rotating black hole (aka every black hole, to some extent), is still a singularity (no need for quotation marks, it still has zero volume) despite not being a point. It's a ring with zero cross-sectional area, sort of like an infinitely thin thread arranged in a circle.

Furthermore, this thread is based on quibbling over semantics without really understanding what the author quite validly meant. The "black hole" aspect of a singularity is a description of the effects of its event horizon, which of course scales with mass. A more massive black hole is by definition larger then a less massive black hole. Someone mod this up so this misunderstanding can be cleared up for more people.

Re:eh? I don't get it? (4, Informative)

pclminion (145572) | more than 6 years ago | (#22000992)

A black hole has an event horizon. This horizon has a very well-defined size.

500 AU event horizon (1)

peter303 (12292) | more than 6 years ago | (#22001464)

BIG 2.7 km per solar mass.

correction: 325 AU (2, Funny)

peter303 (12292) | more than 6 years ago | (#22001552)

used miles instead of km for AU :-)

Re:correction: 3.6 x 10^2 AU (0)

Anonymous Coward | more than 6 years ago | (#22002220)

Further corrected to 3.6 x 10^2 AU.

Google never lies.
Interestingly, this means the relevant density of the black hole (assuming it is spherical, which it almost certainly isn't, but that's a nigh-negligible correction) is 5.7 x10^-5 g cm^-3, or roughly comparable to the density of hydrogen at room temperature.

Re:eh? I don't get it? (4, Informative)

moderatorrater (1095745) | more than 6 years ago | (#22001198)

The event horizon is often considered the size of a black hole since nothing could ever leave that space.

Black Hole size - 20 Questions (1)

ginbot462 (626023) | more than 6 years ago | (#22002588)

It's funny ... I've always wondered about how to describe the "size" of a blackhole too. Especially when playing this Q20 [thinkgeek.com] . BTW .. it seemed when I thought of the singularity as the size it got it wrong. But, if I thought of being massive, it would guess black hole.

Off-topic: for anyone that has played with the Q20, what are some interesting things you got it too guess? It doesn't seem to do well with risque things (think of the children!). I'll give you a hint ... Q20 guessed 'toy'. My reply: Yes, sometimes that is how they are marketed.

Re:eh? I don't get it? (2, Informative)

jgarra23 (1109651) | more than 6 years ago | (#22003836)

How large can a singularity be?

I mean, if they used the word "massive" I'd get it. But large?


I believe they are measuring the event horizon, not the singularity.

Goatse? (-1, Redundant)

Fear the Clam (230933) | more than 6 years ago | (#22000622)

No, wait. He's a red giant.

Wow thats bigger than Goatse! (-1, Flamebait)

Anonymous Coward | more than 6 years ago | (#22000684)

Clinton/Obama 08! 2 aholes

Re:Wow thats bigger than Goatse! (-1, Flamebait)

Anonymous Coward | more than 6 years ago | (#22000908)

Only one is black though, I just can't figure out which!

Re:Wow thats bigger than Goatse! (-1, Flamebait)

Anonymous Coward | more than 6 years ago | (#22001058)

That's funny, I can't figure out which one is a woman.

Wow. (4, Funny)

AltGrendel (175092) | more than 6 years ago | (#22000692)

A binary black hole system.

Proctologists across the globe swoon!

Re:Wow. (0)

Anonymous Coward | more than 6 years ago | (#22001222)

Whoever tagged this article "goatse" almost caused me to spit coffee on my keyboard.

that's a lot (1, Informative)

ILuvRamen (1026668) | more than 6 years ago | (#22000704)

I'll save you all the time of googling this cuz I know you wanna know too. There's 200-400 billion stars in the milky way for example but most are bigger than our sun I think. So 18 billion solar masses is A LOT of stars to suck up in one galaxy. Geeze the think probably looks like a big donut by now.

/Homer (0, Offtopic)

ByOhTek (1181381) | more than 6 years ago | (#22000804)

mmmmm. Donut.

Re:that's a lot (3, Informative)

Anonymous Coward | more than 6 years ago | (#22000922)

My googling says its even more impressive (http://curious.astro.cornell.edu/question.php?number=31) 100 billion stars in the Milky Way and most are smaller than the sun, so 18 billion makes it very greedy indeed!

Re:that's a lot (4, Funny)

HAKdragon (193605) | more than 6 years ago | (#22002004)

Hawking: Homer, your theory of a donut shaped universe intrigues me

no pictures (0, Redundant)

juan2074 (312848) | more than 6 years ago | (#22000764)

Please keep the goatse.cx references to a minimum.

Re:no pictures (-1, Offtopic)

peipas (809350) | more than 6 years ago | (#22000870)

Didn't it change to goatse.cz?

Re:no pictures (0)

Anonymous Coward | more than 6 years ago | (#22001444)

I just tried goatse.cz and goatse.cx. Neither of them are working for me today. But http://www.goatse.ch/ [goatse.ch] worked, except they've changed it by adding some weird political theme.

Re:no pictures (3, Insightful)

Arthur Grumbine (1086397) | more than 6 years ago | (#22003766)

Neither of them are working for me today

"Today"?! How often do you feel the need to stare at a gaping anus?!?

largest black hole yet discovered (-1, Redundant)

CodeBuster (516420) | more than 6 years ago | (#22000862)

I thought that goatse.cx had that rather dubious distinction...

so is Rosie orbiting Oprah, or vice versa? (2, Funny)

ImYY4U (539546) | more than 6 years ago | (#22000894)

Which one weighs 18 billion times our sun, and which ones weighs 100 million times our sun?

Re:so is Rosie orbiting Oprah, or vice versa? (-1, Flamebait)

ImYY4U (539546) | more than 6 years ago | (#22000976)

oops, my bad, i thought they said two biggest black ho's...

Re:so is Rosie orbiting Oprah, or vice versa? (1, Informative)

ImYY4U (539546) | more than 6 years ago | (#22001092)

oops again, Rosie's not black!

Re:so is Rosie orbiting Oprah, or vice versa? (1)

R2.0 (532027) | more than 6 years ago | (#22003070)

Puhlease - assuming that all ho's are African American is racist. There is a whole RAINBOW of ho's out there, in every race, shape, and size.

Ask slashdot (4, Funny)

sm62704 (957197) | more than 6 years ago | (#22000914)

Is there a theoretical limit to the size of a black hole?

That was serious, here's the link [uncyclopedia.org] to the non-serious.

A Black hole is an impossible object which makes the Universe work. It has the useful property of being "undetectable". It's like when your spouse comes home with a dent in the car, and blames it on an invisible black mass; the dent is proof of the black mass, but you can't, and never will be able to see it with CCTV cameras, but you know it's there. "Dark matter" is an equally undetectable force that causes cars to defy gravity, and hit invisible black holes. Astronomers will tell you that lots of them have spouses with dents in their cars, and can explain this is very technical terms, so you won't be able to understand why it's not possible.
More there...

Re:Ask slashdot (1)

mea37 (1201159) | more than 6 years ago | (#22001192)

I don't think such a limit is known. (Well, unless you care to calculate the size of a black hole containing all of the matter and energy in the Universe and count that as a theoretical limit...) But I also don't think we know enough about black holes to say that with any certainty.

Re:Ask slashdot (4, Informative)

ArcherB (796902) | more than 6 years ago | (#22001522)

Is there a theoretical limit to the size of a black hole?
While I can't give you numbers since I'm going from memory, but there used to be a theoretical limit to black hole size. This was before "Super Massive Black Holes" were discovered in the center of every galaxy. Super Massive Black Holes are much more massive than the previous theoretical limit and were thought to be impossible so many astronomers were claiming that such a thing was couldn't exist while others were saying, "Oh yeah? Then why don't you put down the chalk, professor, and come down to my observatory and tell me what that big-ass black gravity thing is in the middle of our galaxy!" (Of course, they couldn't really see it, but you get the point)

I think astronomers are reluctant to guess at a size limit now as they don't want another discovery to make them look like asses.

Re:Ask slashdot (2, Informative)

Ambitwistor (1041236) | more than 6 years ago | (#22002772)

While I can't give you numbers since I'm going from memory, but there used to be a theoretical limit to black hole size.
There has never been a theoretical limit to the size of a generic black hole. (Technically, the observable universe could be in a giant black hole.) But back when people thought the only way a black hole could form was from the collapse of a single star, there was a practical limit on the size of an astrophysical black hole: if it forms from stellar collapse, it can't be more massive than the most massive stars. Everyone recognized that black holes can get larger by swallowing more mass, but it was a long time before people seriously considered the possibility of supermassive black holes actually existing.

Re:Ask slashdot (2, Informative)

Cassini2 (956052) | more than 6 years ago | (#22003260)

The Eddington limit [wikipedia.org] appears to limit the size of a star. At one point in time, it was thought that black holes formed from the collapse of stars. Later on, it was concluded that supermassive black holes are very good at feeding on neighboring stars, and thus supermassive black holes could form. The Wikipedia page on Black Hole Parameters [wikipedia.org] has an explanation.

Re:Ask slashdot (1)

DarthVain (724186) | more than 6 years ago | (#22003552)

There was a post on slashdot I think in the past year on this subject.

Where scientists found a black hole seemingly larger than it was possible to be.

I think the difference is, while it is postulated that there are super massives at the center of every galaxy, what is not known is how they are formed.

As is commonly accepted, a normal black hole is formed by a collapsing star, and that stars have a finite size, that any black hole formed in this manner is restricted.

If I remember correctly there was also a threshold to which a black hole could eat up matter and grow, but at a certain point it could not any more for some reason (either due to loss somehow equaling the gain, or a change would occur).

I think it was thought that the super massives are formed through some other method not yet understood, and as I recall the largest possible normal black hole was some magnitude of 8 or 16 of something (I know that is not very helpful), and the one in question was like 16.7 or something like that.

Anyway I am positive that it was on slashdot, so if someone wants to search it out and post it, be my guest. My mind is a black hole, nothing escapes!

Re:Ask slashdot (1)

DarthVain (724186) | more than 6 years ago | (#22003648)

I know it is bad form to answer your own post, but I was curious if I was losing my mind. Anyway here are the links.

Slashdot:
http://science.slashdot.org/article.pl?sid=07/10/17/2257234 [slashdot.org]

Article:
http://www.space.com/scienceastronomy/071017-monster-bhole.html [space.com]

I was pretty close.

Spitzer Space Telescope? (-1, Troll)

adavies42 (746183) | more than 6 years ago | (#22000952)

The Spitzer Space Telescope? For finding governor Eliot's ethics?

When it comes to choosing neighbors, (2, Funny)

davidsyes (765062) | more than 6 years ago | (#22001100)

I pine for Sol, not a massive black hole. Otherwise, we'll have a massive cleanup job? Oh, wait...

Re:When it comes to choosing neighbors, (1)

geekoid (135745) | more than 6 years ago | (#22001138)

ok, that was bad.
Not "hahaha man that was bad haha." just lame.

orbiting blackholes? (1)

buttle2000 (1041826) | more than 6 years ago | (#22001102)

That's not a solar system, so what do you call it, a blackhole system?

Re:orbiting blackholes? (1)

frizop (831236) | more than 6 years ago | (#22001328)

This is what I was wondering. Just the idea that a black hole could orbit another black hole is rad.

Re:orbiting blackholes? (2, Interesting)

AbsoluteXyro (1048620) | more than 6 years ago | (#22002342)

It could be argued that the singularity of a black hole is an impossibly dense star. In which case, it would still be a solar system. However, it would only be a solar system if it had planets orbiting around it. It is highly unlikely that a black hole would have planets orbiting it, as the planets would have insufficient mass to keep from simply falling in to the black hole, that is to say the overwhelming mass of the black hole would place the barycenter of the black hole and any accompanying planet well inside the event horizon, and the orbital velocity that would be required to prevent simply being sucked in would be nigh unthinkable. A pair of black holes orbiting each other would be a binary system, just like two stars orbiting each other.

Re:orbiting blackholes? (4, Informative)

Ambitwistor (1041236) | more than 6 years ago | (#22003074)

It is highly unlikely that a black hole would have planets orbiting it, as the planets would have insufficient mass to keep from simply falling in to the black hole,
If the Sun collapsed into a black hole, its gravitational pull on the Earth wouldn't change.

that is to say the overwhelming mass of the black hole would place the barycenter of the black hole and any accompanying planet well inside the event horizon,
Maybe you're talking about supermassive black holes, but if you're talking about black holes in solar systems, formed from collapsed stars, that's not true. A black hole is not "overwhelmingly massive"; it generally has less mass than the star it formed from, since some mass may be lost during the collapse. (Unless it gains a lot more later ...)

Furthermore, as the Earth-Sun barycenter is well outside the Sun's Schwarzschild radius, it would be outside the event horizon of a solar-mass black hole, too. Not that the location of the barycenter even matters to the stability of the orbit.

There are exoplanets — the first discovered, actually — known to orbit neutron stars, which are only 10-20 km in radius. There's no reason why planets couldn't orbit black holes too.

Re:orbiting blackholes? (1)

AbsoluteXyro (1048620) | more than 6 years ago | (#22003336)

You find me a single solar mass black hole and I'll be inclined to believe you.

Re:orbiting blackholes? (2, Informative)

Ambitwistor (1041236) | more than 6 years ago | (#22003440)

The existence of a single solar mass black hole has nothing to do with any of the facts I stated. They hold no matter what the mass of the black hole, so long as it's not comparable in size to the planet's orbit itself.

(FYI, the smallest known black hole candidates are about 3 solar masses, with a size of about 18 km in diameter, i.e., about half the size of a neutron star.)

Re:orbiting blackholes? (3, Interesting)

sentientbeing (688713) | more than 6 years ago | (#22002938)

A holer system.

Ugh, the jokes aren't even funny anymore... (2, Funny)

AndGodSed (968378) | more than 6 years ago | (#22001106)

Seems like /. is going down one of them two holes...

Re:Ugh, the jokes aren't even funny anymore... (1)

Cro Magnon (467622) | more than 6 years ago | (#22003092)

Yes it is. And that really sux!

Need a better measurement comparison (4, Funny)

vjmurphy (190266) | more than 6 years ago | (#22001160)

"largest black hole yet discovered, weighing in at 18 billion times the mass of Sol."

Yes, but how many Twinkies is that?

Re:Need a better measurement comparison (1)

Bruiser80 (1179083) | more than 6 years ago | (#22001274)

Are we talking regular twinkies, or 35ft-long 600-lb ghostbusting twinkies? (yes I had to check imdb.com for the weight, I suck)

Re:Need a better measurement comparison (5, Funny)

wizardforce (1005805) | more than 6 years ago | (#22001346)

Yes, but how many Twinkies is that?
heh.. just for the heck of it: mass of twinkie: ~35 grams, mass of sun =2*10^30 kg, mass of blackhole: 18*10^9 sol therefore, 18*10^9*2*10^30/35g*1000g/kg~= 10^42 twinkies.

Re:Need a better measurement comparison (0)

Anonymous Coward | more than 6 years ago | (#22001496)

"heh.. just for the heck of it: mass of twinkie: ~35 grams, mass of sun =2*10^30 kg, mass of blackhole: 18*10^9 sol therefore, 18*10^9*2*10^30/35g*1000g/kg~= 10^42 twinkies."

But the real question is, how does that compare to the number of twinkies consumed in the US each year?

Re:Need a better measurement comparison (1)

PakProtector (115173) | more than 6 years ago | (#22002078)

"heh.. just for the heck of it: mass of twinkie: ~35 grams, mass of sun =2*10^30 kg, mass of blackhole: 18*10^9 sol therefore, 18*10^9*2*10^30/35g*1000g/kg~= 10^42 twinkies."

But the real question is, how does that compare to the number of twinkies consumed in the US each year?

Well, This [wikipedia.org] says that 500 million Twinkies are produced each year.

So it would take around 2.0 × 10^39 years to make enough twinkies to make that Black Hole.

Re:Need a better measurement comparison (1)

wizardforce (1005805) | more than 6 years ago | (#22002116)

1.028*10^42/(5*10^8)= 2.056*10^33 years

Re:Need a better measurement comparison (3, Funny)

networkBoy (774728) | more than 6 years ago | (#22001850)

You know, somehow that 42 is the exponent for number of twinkies in a black hole makes me worry about life, the universe, and everything....
-nB

Re:Need a better measurement comparison (2, Insightful)

protolith (619345) | more than 6 years ago | (#22002080)

Or you could say a Twinkie approximately 10^38 km long and weighing 3.5*10^37 metric tons.

Or 3.685*10^29 AU, (3.24810^24 Parsecs), 1.05*10^25 light years, room for about a billion of these in the universe!

"That's a really big Twinkie"

Re:Need a better measurement comparison (1)

cstdenis (1118589) | more than 6 years ago | (#22001398)

How many libraries of congress?

9.8 × 10^50 twinkies (1)

MyNymWasTaken (879908) | more than 6 years ago | (#22001556)

Mass of an ordinary Twinkie: 36.4 g
http://www.mctague.org/carl/fun/twinkie/ [mctague.org]

Mass of the Sun: 1.99 × 10^33 g
http://www.google.com/search?hl=en&q=mass+of+the+sun&btnG=Google+Search [google.com]

1 solar mass = 5.47 × 10^31 twinkies

9.8 × 10^42 twinkies (1)

MyNymWasTaken (879908) | more than 6 years ago | (#22001596)

Mental glitch - 18 billion = 1.8 × 10^9 ... not 18 × 10^18

I'm glad it's Friday. *headdesk*

Re:9.8 × 10^42 twinkies (1)

wizardforce (1005805) | more than 6 years ago | (#22001968)

actually it's 1.8*10^10 not 1.8*10^9 (10^9=billion, 18 billion= 18*10^9=1.8*10^10)
2*10^30*1.8*10^10=3.6*10^40
3.6*10^40*10^3= 3.6*10^43
3.6*10^43/35=1.028*10^42

The Mass of a Hole? (1)

BigAssRat (724675) | more than 6 years ago | (#22001294)

What exactly is the mass of a hole? Besides a donut hole.

Re:The Mass of a Hole? (1)

El_Smack (267329) | more than 6 years ago | (#22001410)

"What exactly is the mass of a hole? Besides a donut hole."

Well, I've read comments here over the years that prove the existence of Mass Holes.
Now I suppose we just find those users and weigh them.

Re:The Mass of a Hole? (0)

Anonymous Coward | more than 6 years ago | (#22002704)

If you want to prove the existence of Mass Holes, just visit New Hampshire. They're taking over the state.

Re:The Mass of a Hole? (2, Informative)

Mantaar (1139339) | more than 6 years ago | (#22001516)

A "black hole" is not a hole like in your cheese - it's just a very sloppy term for an actual object with a higher-than-usual mass. So high, that it swallows all the light it might emit otherwise and thus appears to be totally black. Due to it's (assumed) look it's been dubbed a "black hole", though it's not really a hole - and it probably wouldn't be too dark around it, too...

The Hawking Evaporation or just random stuff that's falling into it (gas, particles) should emit a considerable amount of light. Within the Event Horizon, of course, everything's pitch dark. So, the thing should actually look like a Space Donut.

Re:The Mass of a Hole? (1)

R2.0 (532027) | more than 6 years ago | (#22003152)

"Within the Event Horizon, of course, everything's pitch dark."

I always thought it depended on where you looked. If we suspend physics and assume that one could take measurements inside the event horizon, wouldn't those detectors "see" a whole shitload of photons coming in from the outside?

Re:The Mass of a Hole? (1)

Ambitwistor (1041236) | more than 6 years ago | (#22003774)

If we suspend physics and assume that one could take measurements inside the event horizon, wouldn't those detectors "see" a whole shitload of photons coming in from the outside?
Yes. This Java applet [netspace.net.au] has a visualization (if you set the observer distance to less than the Schwarzschild radius at 2.0 M. You should rotate the view to face outward.)

(There's no need to "suspend physics"; there's no physical reason why you can't take measurements within an event horizon, as long as you're comfortable with the fact that you'll die soon afterward and won't be able to transmit your data to anyone outside of the hole).

holy hole (1)

nategoose (1004564) | more than 6 years ago | (#22001432)

This is truly the holiest of holes!

Re:holy hole (0)

Anonymous Coward | more than 6 years ago | (#22001606)

Why don't you do everyone a favour and crawl back into it then, spare everyone from your sense of humour?

Gravity & Levity together in a black-hole (1)

OldHawk777 (19923) | more than 6 years ago | (#22001614)

Yes, there is much gravitational distortion around a black-hole,
which looks like a very light-bright sphere (maybe a little
physically distorted) to all humans, and within the absence of
light there is much levity to consider.

Tell me again, why is it a big black-hole and not a big bright-spot?

In the absence of levity there is gravity.
In the absence of gravity there is levity.

Re:Gravity & Levity together in a black-hole (1)

MikeDirnt69 (1105185) | more than 6 years ago | (#22002088)

Tell me again, why is it a big black-hole and not a big bright-spot?

Because the Black Hole generates the Bright Spot, not the opposite.

Tag as Sun!Sol (2)

MtlDty (711230) | more than 6 years ago | (#22001670)

Why do people say 'sol' instead of 'sun'. Is there some fundamental difference, or are they just trying to sound smart?

Re:Tag as Sun!Sol (2, Informative)

AbsoluteXyro (1048620) | more than 6 years ago | (#22002140)

We're pretty used to referring to Sol as "the sun" but the truth is, a sun is a thing and there are many of them. It is silly to call ours THE sun, because it clearly isn't. In actually, it is ONE OF the suns. Sol is our sun's Latin name. Similarly, Luna is our moon's Latin name.

Re:Tag as Sun!Sol (2, Insightful)

kalirion (728907) | more than 6 years ago | (#22002862)

It's equally silly to say The White House when there are plenty of white houses around, no?

Re:Tag as Sun!Sol (1)

mevets (322601) | more than 6 years ago | (#22004266)

Wouldn't it be more pretentious to use an even less lively language, aramaic perhaps? If somebody is confused by the expression "18 times the mass of the sun", they need to spend more time outdoors, among the living.

Re:Tag as Sun!Sol (0)

Anonymous Coward | more than 6 years ago | (#22002790)

sol is our sun's name.
or sol is our star's name.
or ah never mind.

Re:Tag as Sun!Sol (1)

pembo13 (770295) | more than 6 years ago | (#22002850)

sun is 'common noun' ; sol is 'proper noun'

Re:Tag as Sun!Sol (1)

Chrutil (732561) | more than 6 years ago | (#22002980)

>> Why do people say 'sol' instead of 'sun'.
Perhaps they are from Sweden?

gridwars (2, Informative)

doti (966971) | more than 6 years ago | (#22001690)

This story makes me want to play gridwars2 [marune.de] again.

And again, and again...

Question about gravity (5, Interesting)

caywen (942955) | more than 6 years ago | (#22001754)

One question I have about gravity and black holes is this: If nothing can escape the event horizon, how can gravity escape it? In other words, would objects outside the event horizon ever feel the pull of gravity from that which is inside the event horizon?

Re:Question about gravity (2, Insightful)

fred fleenblat (463628) | more than 6 years ago | (#22002254)

gravity *waves* cannot escape the event horizon, so presumably something like a starquake of the singularity cannot be detected. however, the gravitational field around the black hole is/was established before stuff falls in so as far as the rest of the universe is concerned the black hole has normal gravity. there's some weird effects like frame dragging though. check wikipedia for some explanations. IANAP.

Re:Question about gravity (3, Interesting)

Anonymous Coward | more than 6 years ago | (#22002674)

Gravitational pull isn't something that is being radiated out of bodies. Just changes of it.

(In fact if the singularity somehow disappeared magically the outside world wouldn't detect it since the signal of black hole disappearing wouldn't escape from the gravitational well.)

Re:Question about gravity (3, Informative)

Ambitwistor (1041236) | more than 6 years ago | (#22002816)

Other people have answered your question (radiation cannot escape from inside the horizon, but it can still generate a static external field), but here [ucr.edu] is a FAQ with more detail, including the quantum picture.

Re:Question about gravity (2, Insightful)

JohnFluxx (413620) | more than 6 years ago | (#22002982)

One hypothesis of gravity is that it is an exchange of 'gravitons'. If this hypothesis is indeed correct, then it does indeed make sense to ask how these gravitons can escape a black hole. And I don't know the answer to that.

But the most commonly accepted theory is that heavy objects cause the fabric of spacetime to bend under its mass - like a heavy ball placed on rubber sheet.
With this image, it is spacetime that bends so there's no meaningful question for how gravity 'escapes' from it.

Re:Question about gravity (2, Informative)

Ambitwistor (1041236) | more than 6 years ago | (#22003814)

One hypothesis of gravity is that it is an exchange of 'gravitons'. If this hypothesis is indeed correct, then it does indeed make sense to ask how these gravitons can escape a black hole. And I don't know the answer to that.
Static gravitational fields are mediated by virtual gravitons, which can travel at any speed, including faster than light. However, you cannot use them to transmit information, i.e., changes in the field from inside the horizon.

With this image, it is spacetime that bends so there's no meaningful question for how gravity 'escapes' from it.
Right. Classically you can see that the exterior field does not depend on the interior field, and that gravitational radiation generated inside the hole can't get out.

Re:Question about gravity (1)

autophile (640621) | more than 6 years ago | (#22003318)

I'm taking a wild guess here (a little knowledge is a lot dangerous). Forces are understood by the Standard Model of physics to be implemented via mediating particles [wikipedia.org] . That is, a force between two particles is felt when those two particles exchange a mediating particle. The photon is considered the mediating particle of the electromagnetic force, and the graviton is hypothesized to be the mediating particle of the gravitational force.

However, the mediating particles themselves are not affected by the force they mediate. Otherwise the universe would disappear up its own arse.

Hence, gravity is not affected by gravity.

--Rob

Re:Question about gravity (0)

Anonymous Coward | more than 6 years ago | (#22003610)

However, the mediating particles themselves are not affected by the force they mediate.

Well, actually the mediating particles of the strong force are affected by their own force, which leads to all sorts of hilarity.

At least, "hilarity" by my standards.

Re:Question about gravity (2, Interesting)

Ambitwistor (1041236) | more than 6 years ago | (#22003670)

However, the mediating particles themselves are not affected by the force they mediate. Otherwise the universe would disappear up its own arse.
Hence, gravity is not affected by gravity.
Actually, most mediating particles are affected by the force they mediate, including gluons, the hypothetical gravitons, and IIRC the W bosons.

In gauge theory, a non-Abelian gauge group will in general lead to a nonlinear Yang-Mills theory with self-interacting fields, in contrast to the linear Abelian theory of electrodynamics.

Because gluons, the mediator of the strong nuclear force, themselves carry strong ("color") charge, it's possible for them to bind to each other. (See glueballs [wikipedia.org] in quantum chromodynamics.)

Similarly, gravity gravitates: gravitons interact with each other, because they have energy and anything with energy gravitates. This idea holds even in classical general relativity: gravitational fields themselves gravitate. Analogously to QCD glueballs, general relativity can have gravitational geons [wikipedia.org] , which are regions of gravitational field which hold themselves together under their own gravity. (You might think that a vacuum black hole has that property too, but I'm talking about purely non-singular field configurations.)

Re:Question about gravity (1)

kapouer (1215366) | more than 6 years ago | (#22003594)

apparently general relativity explains this by bending [ucr.edu] space-time.
So a black hole is a space-time bender...

Re:Question about gravity (1)

jollyreaper (513215) | more than 6 years ago | (#22003706)

One question I have about gravity and black holes is this: If nothing can escape the event horizon, how can gravity escape it? In other words, would objects outside the event horizon ever feel the pull of gravity from that which is inside the event horizon?
Here's an even better question. If I used my magic obliterator to magically make the sun disappear, would Earth go flying off into space at the same moment or would it continue to orbit the missing sun for the 8 minutes it would take the last rays of light to reach us? Me not being a scientist, I would think immediately but I'm wrong. Knowledgeable people say the Earth would continue for those 8 minutes because nothing can communicate faster than the speed of light, violating causality and everything. This is where they say gravitons come in as a particle that conveys gravity which doesn't make any sense.

All of this particle physics stuff makes me feel like someone is pulling my leg like with Scientology. Of course, the damndest thing is when they can experimentally validate the theories that don't make any logical sense. As one observer pointed out, the human mind is used to dealing with things in a human environment on a human scale, not too big and not too small. Therefore when we probe into the worlds of the subatomic and the cosmic, what we observe defies our sense of order and rationality but just because we have trouble understanding it doesn't make it less true.

Re:Question about gravity (2, Informative)

Ambitwistor (1041236) | more than 6 years ago | (#22003888)

If I used my magic obliterator to magically make the sun disappear, would Earth go flying off into space at the same moment or would it continue to orbit the missing sun for the 8 minutes it would take the last rays of light to reach us?
The latter.

This is where they say gravitons come in as a particle that conveys gravity which doesn't make any sense.
Why doesn't it make any sense? Photons are particles which convey electric and magnetic forces, do you have a problem with them too?

Anyway, you don't need to appeal to graviton particles to answer the above question. Even in classical general relativity, the answer is still "8 minutes later", since that's how long for gravitational waves of spacetime curvature, traveling at the speed of light, take to reach the Earth.

That's incredible! (5, Informative)

renfrow (232180) | more than 6 years ago | (#22001794)

Using this illustration [astro.utu.fi] and my trusty piece of paper straight edge, I estimate the long axis of the orbit to be 21000 AU and the minor axis to be 16000 AU. Using Ramunjan's Approximation [wikipedia.org] for the circumference of the elliptical orbit and converting to light years [glyphweb.com] , I guesstimate the circumference of the orbit to be ~1.99 (call it 2) light years.

For a 12 year orbital period this means that the orbiting black hole is AVERAGING 1/6c (~49965km/sec, call it 50k km/sec)... meaning at periquaserion it's really booking! Much faster than The Dash!

Tom.

And so... (3, Funny)

Cleon (471197) | more than 6 years ago | (#22001878)

I think this finally means that we have a definition for the SI unit "fuck-ton."

Speed? (1)

tbischel (862773) | more than 6 years ago | (#22002314)

How fast is the smaller black hole traveling at perigee, relatively speaking?

how did they... (-1, Troll)

Anonymous Coward | more than 6 years ago | (#22002326)

Get to my ex-husband butt?

Re:how did they... (-1, Troll)

Anonymous Coward | more than 6 years ago | (#22002726)

Hey look! A woman made a stupid, corny, retarted joke. Just like every woman makes... because they can't figure out how to be funny... they just know how to slag Men.

Say NO to women's rights. Forcefully.

Re:how did they... (1)

Arthur Grumbine (1086397) | more than 6 years ago | (#22004024)

Is it just me or does it seem like AC-2 is probably AC-1's ex-husband?

Orbital speed (0)

Anonymous Coward | more than 6 years ago | (#22002372)

If the numbers in the BBC article are correct, the orbit has an extent of 1.5 light years and period of 12 years. That means the orbital velocity is a sizable fraction of the speed of light, an average of at least 0.25c!

Missing joke (0)

Anonymous Coward | more than 6 years ago | (#22002802)

You know, I'm really surprised no one has posted a goatse joke yet...

Sol (0, Troll)

errxn (108621) | more than 6 years ago | (#22003166)

...otherwise known as *the Sun*. I mean, can we get just a little more pretentious?
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