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Largest Black Hole Measured
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.
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!
A black hole has an event horizon. This horizon has a very well-defined size.
oops again, Rosie's not black!
"Know but never fear the consequences of your actions."
The event horizon is often considered the size of a black hole since nothing could ever leave that space.
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.
I'm an infovore...
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.
There is no "I disagree" mod for a reason. Flamebait, Troll, and Overrated are not substitutes.
This story makes me want to play gridwars2 again.
And again, and again...
factor 966971: 966971
Using this illustration 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 for the circumference of the elliptical orbit and converting to light years, 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.
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.
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$.
Other people have answered your question (radiation cannot escape from inside the horizon, but it can still generate a static external field), but here is a FAQ with more detail, including the quantum picture.
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.
The Eddington limit 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 has an explanation.
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.)
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.
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.
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.
Actually, my understanding is that the most common stars in the galaxy are Red Dwarfs, and thus smaller than our sun. (Yup, NASA confirms: http://planetquest.jpl.nasa.gov/glossary/red_dwarf.html)
why many suns? it's more like they are many stars and our star is name the sun!
similarly, the moon is the name of the Earth natural satellite