Menacingly dark disk of the Milky Way galaxy's central black hole, and the hot gas caught in its gravity, could look like this computer simulation
when a network of radio telescopes begins observing next year. Interstellar gas will, however, blur the finer details.
Image: Courtesy of Avery E. Broderick
In Brief
- Black holes are among the most mysterious objects in the universe. So far astronomers have observed them only indirectly, from their gravitational effects on stars and from the radiation emitted by hot gas spiraling toward them.
- Astronomers are adapting a network of radio telescopes to produce images of the supermassive black holes that lie at the center of the Milky Way and M87 galaxies.
- Better studies of black holes not only would help explain unusual phenomena produced by the holes but also could test Einstein’s theory of general relativity and provide vital insights into the nature of gravity in extreme situations.
You have probably seen the TV commercial in which a cell phone technician travels to remote places and asks on his phone, “Can you hear me now?” Imagine this technician traveling to the center of our Milky Way galaxy, wherein lurks a massive black hole, Sagittarius A* (Sgr A*), weighing as much as 4.5 million suns. As the technician approached within 10 million kilometers of the black hole, we would hear his cadence slow down and his voice deepen and fade, eventually turning to a monotone whisper with diminishing reception. If we were to look, we would see his image turn increasingly red and dim as he became frozen in time near the black hole’s boundary, known as the event horizon.
The technician himself, however, would experience no slowing of time and would see nothing strange at the location of the event horizon. He would know he had crossed the horizon only when he heard us say, “No, we cannot hear you very well!” He would have no way of sharing his last impressions with us—nothing, not even light, can escape from gravity’s extreme pull inside the event horizon. A minute after he crossed the horizon, the gravitational forces deep inside the hole would tear him apart.
This article was originally published with the title Portrait of a Black Hole.
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16 Comments
Add CommentBroderick and Loeb's article on black holes highlighted a hole in my understanding. Assuming such a black hole existed, time reversal is still retained for anything outside because it takes - as seen from outside - forever for it to fall in. And wouldn't the in-falling cell phone tech be incinerated in a flash of Hawking radiation as the black hole evaporated before he could complete his plunge in? Going really far, how do we know a black hole could really form in finite time? Can you really distinguish between a true black hole and a lot of matter that's been falling toward but never reaching a nascent event horizon for a long, long time?
Reply | Report Abuse | Link to thisBroderick and Loeb's article on black holes repeatedly refers to a black hole's "weight" and to "weighing" a black hole. Ugh. Were those word choices due to the authors or to the SciAm writer? "Weight" should not be swapped with "mass", which would have been the more correct wording. Weight of an object involves the product of the mass and the gravity field to which the mass is subject, while mass is a property of the object itself.
Reply | Report Abuse | Link to thisThat article sounds rather bunk. I've wondered recently though, if gravity could be disabled locally by a device, what would you get by applying it to a black hole? I know that space would snap back to its original size since the gravity of the singularity is no longer distorting it, but what would that look like? A flawless sphere with no imperfections composed of elementary particles compressed so tightly that even vibration is impossible? I'd assume it would be accelerated by the restoration of time to an angular velocity nearly unfathomable but at the same time unnoticeable due to the perfection in its surface.
Reply | Report Abuse | Link to thisJust some food for thought about black holes.
Where and what is on other side of a black hole? Endless space? Could it be entrance to other universes?
Reply | Report Abuse | Link to thisThanks.
Bill Kraham
The Word "Black Hole" is misleading. It should rather be called a huge accumulation of matter producing an enormous amount of gravitational pull that no mass or light can escape whenever it comes close to this location.
Reply | Report Abuse | Link to thisThe basic principle of general relativity is the equivalence of gravitational mass and inertial mass.
Reply | Report Abuse | Link to thisPortrait of a Black Hole shows that inside the event horizon of a non-rotating, electrically neutral black hole the light cone is tilted towards the singularity; i.e., everything inside that horizon moves towards the singularity. In particular, any virtual gravitons emitted by the singularity will be trapped inside that singularity. Therefore there could be no (quantized) gravitation field outside the singularity and the space around the singularity must be flat. In that case nothing would hinder the virtual gravitons from freely propagating and establish a strong gravitation field which would block the gravitons, etc... Is there a stable self-consistent solution to this conundrum?
Reply | Report Abuse | Link to thisThere are serious problems with General Relativity as applied to black holes. The theory assumes that there is such a thing as a spacetime continuum distinct from gravitational mass which is imbedded in it affecting its curvature. To make the theory work Einstein had to assume that gravitational mass was more or less evenly distributed on a cosmic scale, analogous to a gas. He pointed this problem out in relation to singularities and he doubted that physics could be based on the continuous field concept late in life. The only alternative is a discontinuous universe where space and time derive from the synchronous projection of atomic matter. See the website article Gravity, Quantum Relativity & System 3 at www.cosmic-mindreach.com for a direct derivation of the Lorentz Transformations and what happens to matter on a galactic-cosmic scale. There is indeed an accumulation of quantum energy equivalent to matter beyond an event horizon that is formless and spatially indeterminate but there is no wall of matter accumulated over the life of the galaxy that never completely disappears as seen from the outside. There is no direct empirical evidence to indicate such a phenomenon.
Reply | Report Abuse | Link to thisSome basics for everyone.
Reply | Report Abuse | Link to thisWhen a 'too' massive star can no longer push out it's weight (yes, weight) against the collapsing pull of gravity, the material being crushed at the center acquires a near infinite DENSITY. That point density was originally called a "singularity" Which still holds but whether all the mass is at the point is open for conjecture.
Because a vitual pair coming into existence near an "Event Horizon" has five possible paths to follow 1) both into the hole; 2) one into the hole and the other around the hole; 3) both forward around the hole; 4) one forward and one away from the hole; and, 5) both away from the hole, Hawking radiation cannot occur. The only scenario where one half of the virtual pai disappears is the one where the other half continues on around the hole.
Shells form around the hole outward from the "EH".Within the "EH" nothing escapes (Time is, sorry Albert, Irrelative) next shell level out we find that photons can escape because gravity is not stong enough to halt them from acheiving escape velocity. But that same gravity is strong enough still at this level to halt all other particles from acheiving escape velocity. Next level out we find that now photons and electrons can escape because gravity is not strong enough to prevent them from acheiving escape velocity. All other more massive particles are still at this level, held to being unable to acheive escape velocity. And so foth on out to the level where heavy atomic stuctures aren't held incapable of acheiving escape velocity. I you could see into those two inner shells you would see them as spheres, never glimpsing the "EH". You would see a blue star with majestic twinkling due to the photons and electrons that are able to get away.
That description of a perfect sphere is one from the description of neutron stars not Gravitational Infinities (Ginfins) And matter is embedded onto space-time. Imbedding implies a completely different phenomena about two or more objects occupying the same space whereas to embed means to cause a distortion in something from applying pressure from without.
Now for some points about the article itself. The chart of nearby star orbits covers approximately one half light year (I wish they had made the distance statements in values we are familiar with instead or rather in addition to microarcseconds, making my size statement a guesstimate.)
Reply | Report Abuse | Link to thisThe accompanying accrretion disc illustration shows that the disc should be at least a full light year in radius. This means that all those near orbit stars are traveling within the possible disc space. With that many objects intersecting any conceivable plane, I doubt very much that a disc exists around this gravity well.
What a load of absolute cr_p! It's like the book review of the latest piece of science FICTION.
Reply | Report Abuse | Link to thisWhy are these science-fictionists still basing every space phenomenon on GRAVITY, the weakest force in the universe? Can't they see the real power of the universe? It's right under their noses - MAGNETIC FIELDS everywhere and yet magically divorced from the CURRENTS that create them! Space plasma filaments conduct just fine: current links every galaxy in their clusters and superclusters.
The core of Sagittarius A will be a plasma z-pinch, focus of enormous currents, generating lethal x-rays, etc, just as in the lab. An exceedingly bright 'hole' to frazzle any technician daring to approach!
I also look forward to a better portrait of a black hole. A tornado warps the atmosphere of earth. How do curves of warp of around a black hole differ from curves of isobar around a tornado?
Reply | Report Abuse | Link to thisgeometry is not the same as force.
force is inertia in verse fluent pressure differential
Peace
rwjefferson
Black Hole Gravitton - I am not aware that a "Graviton" has been proven to exist. That it is a "virtual Partical", nor that it can exceed the speed of light. If so, how much faster? That is the question: The force of gravity, the escape velocity increases as you approach the Black Hole until it reaches the speed of light, by definition at the Event Horizon. Logically, it must continue increasing from there until it must reach Infinity(?), at the infinately-dense singularity. At what radius is the Graviton's maximum (?) velocity exceeded? Can it reach an infinate velocitgy or instant position displacement? What is "Flat"?
Reply | Report Abuse | Link to thisRef: Rozenblit & Broderiuck's letters on Pg 10, April 2010.
Newton is not correct by saying masses attract each other. Cavendish experiment is false. Actual fact is matter and antimatter attract each other. So no gravity pull. Gravity is push by gravitoethertons at molecular level towards center of earth --we call gravity. Avogadros law is attraction of gas molecule by gravitoethertons. This is due to mono pole magnetism .Our universe is ELECTRO-MAGNETIC due to whirl of gravitoethertons and that is why planets and galaxies rotate . Strength of gravitoethertons dictate rotation and may be different from planets rotation to stars rotation in galaxy. So rotational curves are different. This gravitoethertons is dark energy or expansive space. Outside antimatter universe is dark matter. There is no dark matter in our universe. Black hole is impossible as no theory support. But neutron stars are at the center of galaxy. Read my theories published in ASTRONOMY.NET IN YEAR 2002 AND LINKS AVAILABLE IN --DURGADAS DATTA FACEBOOK--
Reply | Report Abuse | Link to this've ponder B H ever since learning of their hypothetica existence to now when the studies have deduced they are in fact real.But so far I've find no information on their shape(s) The general way they are described is that captured material is going down a well. This analogy doesn't make sense, isn't the material really spiraling into a disc-like center?
Reply | Report Abuse | Link to thisI'm a layman so maybe I'm missing something.
Reply | Report Abuse | Link to thisThe authors state (pp.45)"A 15 solar mass black hole's event horizon would be a mere 90 km dia...". OK with me.
Later "...a 1 bio sun monster would fit...inside Neptune's orbit" (This I reckon is about 14 bio. km circumference). Let's forget about that.
The 90 km dia baby has a (convenient) diameter of ca. 300km.
If "..matter near a stellar mass black hole can complete an orbit in less then a microsecond." then in one second it will travel at least 300 mio. km - or 1,000c.
So where may I have gone wrong?