Nasa noticed a black hole devouring a star a few months ago:
http://www.irishweatheronline.com/news/space/astronomy/nasa-video-shows-black-hole-devouring-star/33484.html
and generated an amazing video animation of the event:
Sweet. I had no idea some particles could escape a black hole.
Technically, there are no particles escaping from within the event horizon of the black hole itself. In-falling material has very high-energy dynamics, which may (and usually does) expel some material away from the immediate neighborhood of the hole.
The high energy of the matter swirling into the accretion disk is the source of the X-rays and Gamma rays detected.
From the article:
I cannot even comprehend that! 3.9 billion years??
I don’t see why we had to wait 3.9 billion years for those eggheads to give us this news. I want to know about these things IMMEDIATELY!
You people and your need for immediate gratification. It’s sickening!
that’s pretty sweet.
I’d like to know:
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how long does your average black hole take to devour your average star? Or, to make it completely relevant, if this black hole decided to gobble up the sun, how long until the sun looks like Death Maul’s light sabre?
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The NASA pictures and video. I understand the video is just an animation, but what about the picture of the event that led NASA to believe that a star was being devoured by the black hole? Was NASA able to actually “SEE” anything, or was this just the result of the energy they measured from this particular spot in the DRACO constellation?
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How do astro-physicists explain the beams of light shooting out from the center of the “doughnut” black hole? The light has to be travelling faster than the speed of light, correct? Since nothing can escape a black hole, including light, how does this happen?
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How many stars can a black hole “eat” before it’s “full”?
I watched 3 episodes of The Wire today, which explains my first thought: Man, it just fucked that shit UP! 
It’s Darth Maul, though Death Maul would make an awesome heavy metal band name.
Man…matter completely destroyed, debris rocketing out…it’s like Cookie Monster in space. I know there’s no sound in space, but I like to imagine a black hole makes an OMNOMNOMNOM sound while it’s devouring a star.
I’m not an astro-physicist so my comments may be way off reality.
The time of devouring a star depends on the trajectory of the star when it reaches the black hole. If it is going straight towards it then it may take milliseconds to disappear, but since most likely it will be on a off tangent trajectory around the black hole, it will take longer depending on speed, vector direction of movement, etc.
The word “see” is vague like most human everyday language. The claim that a star is being devoured by a black hole is the result of physical observations that have been recorded by instruments. We are now at a point where we can safely say that our knowledge about physics is good enough so as to be as accurate as we can comprehend the universe (tricky term), so the statement that a black hole is devouring a star can be considered as very accurate.
It’s not coming from the center of the black hole. The emissions come from matter just before they are engulfed by the black hole… I don’t know enough to be more descriptive than this. The particles shooting out during the process of a star falling into a black hole are not coming from within the black hole.
A black hole as we understand it can never be “full”. It can absorb particles around it at any time. However, according to the latest theories, black holes do evaporate but it takes an unthinkable length of time for them to disappear.
Naxos has explained it well so I have little to add.
The beams from the “poles” of the black hole are particles of the star which are thrown away out by the rotation of the hole. Pulsars do the same thing which is how we detect them.
Its weird to think about but the Universe is criss-crossed by these lighthouse-like beams of high energy particles. We detect them and learn the composition of stars. If such a beam existed near Earth, we’d be dead.
Black holes can be any size. Classical Einsteinian physics says that we cannot know anything about the inside of a black hole = no hair. Hawking discovered that energy is released and thus black holes do have hair. :eek: Eventually they evaporate through a process called Hawking Radiation.
Star Jones has not been fat for awhile now. You need to update your jokes.
Usually, out in the very large universe we happen to be in, when two things are moving toward each other, they don’t collide. They miss. In the case of a black hole, something falling toward it can miss by a very large distance without avoiding getting devoured. It just takes a bit longer. The object goes into orbit, and the natural mechanics of orbits make it “decay” a bit on each trip around. Another natural consequence of the decaying orbit is that one side of the object experiences a different gravitational attraction than the other.
When the object is a star, which is basically a ball of gas, and a black hole, the star tends to get bits stripped off by the tidal forces, and usually rather rapidly. There are also magnetic forces involved, in most “active galactic center” type of black holes. Immense magnetic forces, in fact. The tidal forces rip the star into a disk of orbiting gas, which continues to be drawn into the black hole. The magnetic forces, by a complex, and incompletely described process drive some of the charged particles toward the black hole’s spin axis, both north and south. These forces are present for many light years outward, and continue to accelerate the ions affected for a very long time, eventually causing them to reach very high percentages of light speed. They collide with stuff, and give off high energy electromagnetic light. (X-rays and such) Nothing actually leaves the black hole, but the process slings some of the falling matter off in a way that produces the jets.
If you happen to be somewhere along the path very close to the axis of that black hole, you can detect the red shifted high energy from billions of light years away, billions of years later. From closer distances, you don’t see as much, on account of being vaporized, and becoming part of the beam.
Tris
It’s actually even harder to collide with a black hole than it is to collide with a star. Ordinarily, when we refer to a “collision”, we mean that two objects get so close that their surfaces overlap. But a black hole is extremely small for its mass, so you can get much closer to it without a collision. It is possible for an isolated black hole to capture something passing by into an orbit (this isn’t possible at all with Newtonian gravity), but it’s really, really hard.
As for black holes getting “full”, the more a black hole eats, the bigger it gets, with no known or hypothesized limit. Black hole evolution is limited by the availability of food, not by anything relating to the hole itself. They do decay via Hawking radiation, but the bigger the hole, the slower the evaporation, and all black holes that we know to exist (i.e., any formed from the collapse of a star) are by far easily big enough that the evaporation is negligible. There’s no rule that says black holes smaller than a star can’t exist, and some of those might have significant Hawking radiation, but we know of no way to form such a small black hole in the present Universe (some might have formed during the Big Bang, and there are a few models which suggest particle accelerators might produce extremely small ones).
I have nothing to add except that I think this thread is hella cool. Thanks, guys.
Every quantity of mass has a characteristic Schwarzschild Radius (SR). This radius refers to the distance from the center of mass which, if all the mass were concentrated within this radius, the escape velocity would exceed the speed of light. There is no hard boundary to the Black Hole (BH), and anything significantly exterior to its SR would behave identically to an encounter with a similar quantity of “normal” matter.
In the near vicinity of the SR, however, tidal forces are set up in the approaching matter which tend to stretch it out as it falls in toward the center of the BH. As has already been mentioned, the dynamics of the encounter will be determined by how directly the star, or other object, approached the BH. These same tidal forces are also present when stars come near another star, or some other “exotic” object such as a neutron star. The denser the object, the closer the star may come, without colliding, before the tidal forces rip it to shreds. Black Holes can be some of the densest objects known.
But not necessarily. Given the estimated mass of the observable universe, the calculated SR would be about 10 billion light years. If the mass of the universe were sufficient to halt the expansion of the Big Bang, and eventually collapse in a “Big Crunch”, the SR would be beyond the observable limits of our universe. We would then be living within the Schwarzschild Radius of a Black Hole containing the entire known universe.
The “size” of a BH (its SR) is related to its mass. The observed BH in the referenced article has an estimated mass of as much as eight million stars with the mass of our sun. This would give a SR of about 20-25 million kilometers. An object, such as a star, falling toward this BH could, in principle, take quite a long time to complete its destruction. The usual dynamics of a “near miss” would have the material of the approaching star stripped off into a donut-shaped “accretion disk” around the black hole.
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The answer depends entirely on how closely and directly the trajectory took the star to the black hole, and how “dense” the black hole was. I do not think there is an “average” which would be relevant.
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The galaxy in which this event was observed is 3.9 billion light years from us, so the probability that anything was “observed” in any traditional definition of the word is negligible. As has already been mentioned, however, the instruments which detected the highly-energetic radiation being emitted are as valid a means of “observing” these events as if we could form an optical image.
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The gravitational forces attracting in-falling matter toward the center of the black hole accelerate it to extreme velocities. As the matter swirls around the SR of the black hole, before it crosses the limit and “disappears” into the interior, it forms the “donut” shape accretion disk. The radiation and high-energy particles being generated most easily escape into space through the “holes” at the poles of the disk, forming the “jets” of radiation and material we see. And, no, they are NOT moving faster than light. And they do not come from within the boundary of the black hole, but from the energetic maelstrom immediately surrounding it.
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As I mentioned above, the entire known universe, with all its mass, may well be within the Schwarzschild Radius of an enormous Black Hole, and we would never know it.
In a black hole, if I were just within the SR, would I see the photons that had been reflected off of the OSHA poster on the wall next to me?
According to your sentence above, I would.
Thank you. I’ve always wondered about that.
According to the resources at my disposal, yes, you would see the reflected photons.
In a stellar-mass black hole, normal matter would be ripped to its constituent subatomic components long before it crossed the Event Horizon on its way to the center of the black hole. It would be highly unlikely that you, or your OSHA poster, would survive the transition.
The situation is different in a supermassive black hole, containing the mass of several million to several billion stars. While the supermassive black holes conjectured to exist in the center of many (most?) normal galaxies (and virtually all active galactic nuclei) would most probably rend you to shreds and accelerate your atoms to gamma-ray energies, if the black hole was sufficiently massive, and the Schwarzschild Radius sufficiently great, you might not even be aware that you had crossed an Event Horizon. From the interior, nothing could escape, not even light. But within the SR, your experience would be fundamentally unchanged from what we have now.
Although light traveling outward from the center will never escape, and will eventually slow to a stop at the limit of the Event Horizon, from your position just inside the SR light behaves essentially as you would expect it to. Due to relativistic time-dilation effects induced by the gravity of the black hole, your perception of light striking the poster and being reflected back into your eyes would be almost indistinguishable from “normal”.
Question: is the image in the first link (labeled “NASA image”) another artist’s conception (ho hum) or an actual photograph? I know the movie in the second link is CGI.
I’m wondering if what NASA actually saw/measured is dramatic. I mean, haven’t they been sure they were seeing distant accretion disks and companion stars in the past? What’s different here?