Reply With QuoteTrying to get a handle on the above I have jotted down what I can see happening around a black star.
To an observer where we are ,we wil only see light aproaching in a direct line to our eyes
I think the above post is more related to theoretical Boson or Fermion Stars-just a general lookup of these tells me that they have not been observed to exist and are pure theory. I don't think app;ying these same lensing possibilities to black stars is appropriate. Here is a small quote I read.
So the idea that a black star would be the brightest object around is I think to be discarded . Appreciate the input and I will read up on these but there is a lot of theoretical mumbo jumbo in there about something which does not exist. Come to think of it there is a lot of mumbo jumbo produced to the student to learn rote -so much so we end up not being able to see the wood for the trees5.7 Boson and fermion stars
Spherically symmetric static solutions of Einstein’s field equation coupled to a scalar field may be interpreted as (uncharged, non-rotating) boson stars if they are free of singularities. Because of the latter condition, the Wyman-Newman-Janis metric (see Section 5.6) does not describe a boson star. The theoretical concept of boson stars goes back to [179, 291]. The analogous idea of a fermion star, with the scalar field replaced by a spin 1/2 (neutrino) field, is even older [216]. Until today there is no observational evidence for the existence of either a boson or a fermion star. However, they are considered, e.g., as hypothetical candidates for supermassive objects at the center of galaxies (see [301, 324] for the boson and [335, 325] for the fermion case). For the supermassive object at the center of our own galaxy, evidence points towards a black hole, but the possibility that it is a boson or fermion star cannot be completely excluded so far.
Trying to get a handle on the above I have jotted down what I can see happening around a black star.
To an observer where we are ,we wil only see light aproaching in a direct line to our eyes
Got in a mess with image shack as the first try ended up 2550 wide and even higher--see if this gets it
URL=http://imageshack.us][/URL
Got in a mess with image shack as the first try ended up 2550 wide and even higher--see if this gets it
URL=http://imageshack.us]
The problem with that theory is firstly that the "real" stars close to the black hole would be VERY obvious because of their dopler shift. You will not get this effect with lensing. Stars orbiting on side will have a blueshift while stars on the other a red shift. With gravitational lensing it's easy to determine how far away each star is because of the redshift. The further away an object is, the more redshift it will have. Also whole galaxies would be lensed and appear to surround the black hole. There should be equal numbers of galaxies and stars in the lensed soup. We don't see this.
Light paths might sound like a universal house of mirrors, though the theory has been used before, it does not hold water.
Lets start with something like electrons. If they travel at the speed of light, then they have infinite energy and time is irrelivant to them. By this logic there is only one electron in the whole universe, it's everywhere at once.
Though it's a good theory, it's not correct.
This is not fact. That is opinon, and not a correct one.In fact for every star or galaxy in the universe there are an infinite number of light paths which will pass near or circle the black hole and arrive at our viewing position
Try this logic. If the universe is infinite, then no matter which direction you travel, eventually your path will intersect a star. By this logic no matter which direction you look into space you should see photons coming from that direction. The sky at night should be white, not black.
If you modify this theory so that light paths are bent and eventually a photon will intersect from any direction, you have the same result. A white sky.
The problem with your theory is that it relies on a large numbers of black holes, and they're not all that common. Even if a galaxy does not contain a black hole, its mass is still big enough to provide lensing.
The focal points of the lensing also have to line up. In an infinite universe, the logic requires infinite number of focal points for each and any object. That doesn't happen. Photons may be deflected, but they are scattered, not focused.
Black holes are bright. They're bright red !
They're also bright orange, bright yellow, bright green, bright blue and bright violet !
At the same time, they're also bright Infra Red, and Ultra Violet.
And especially bright in the X-ray spectrum.
This brightness in the X-ray spectrum is the tag that says, "I'm a black hole !"
The dopler shift around this bright object is also another black hole stellar fingerprint.
Back to light paths.
A gravitational lens is NOT like an optical lens as you know it. It's the opposite. A normal optical lens bends like at shallow angles close to the center and sharper angles further out. A gravitational lens is the opposite.
It bends like sharply close to the center and shallower further out.
This has the effect that it can give the lens multiple focal lengths rather than just one like a conventional lens. Here's a good example of the distorted effect. This lensing isn't caused by a single large object like a black hole, it's caused by a whole cluster of galaxies ! Multiple black holes.
This page has an animation so you can see how lensing around a black hole looks.
It's a great little simulation, I like it.
That observation appears to be correct. The black hole at the center of our own galaxy does not appear to be a big bright single massive star.Originally Posted by tytower
Though it is shrouded by the large numbers of stars at the center of our galactic bulge and those of other similar galaxies.
At X-ray spectrum, the picture is a little different and the super heavy bodies in the universe do appear to be the brightest objects.
Quasars are the brightest continous glowing objects.
I don't know what the latest theory is on quasars is, but last I looked they were just distant galaxies or proto-galaxies.
Gamma Ray bursts are probably brighter, though only very short lived. I'm not sure how supernove rate in the brightness scale. Again, they're only very short lived.
There's nothing wrong with your light vectors in your drawings and they are correct (though a little rough) when it comes to describing the function of a black hole to capture light (EMR).
Oh, but there is only one event horizon, not multiples. You're dealing with einstienian physics, not newtonian, and the laws of physics apply uniformly.
But you'll notice, the black hole is scattering your vectors, not focusing them.
On event horizons
Without too much study i note the wikipedia gives :-
Now on my scan the event horizon then is the inner one . Obviously there will be a horizon above which the black star has no effect on passing light.The most commonly known example of an event horizon is defined around general relativity's description of a black hole, a celestial object so dense that no matter or radiation can escape its gravitational field. This is sometimes described as the boundary within which the black hole's escape velocity is greater than the speed of light. While this definition can be made to work, it only does so if the effects of special and general relativity are taken into account. A more accurate description is to note that within this horizon, all lightlike paths (paths light could take), and hence all paths in the forward light cones of particles within the horizon, are warped so as to fall further into the hole. Once a particle is inside the horizon, moving into the hole is as inevitable as moving forward in time (and can actually be thought of as equivalent to doing so, depending on the spacetime coordinate system used).
To make the distinction clearer, some authors refer to their more specific notion of a horizon as an "absolute horizon". In the context of black holes, event horizon almost always refers to the absolute horizon, as distinct from the apparent horizon.
Between the two there will be varying effects and only in this area can any lensing effect be happening
Not that I'm a big fan of wiki, but half your example concurs with wiki's description. But there is no second horizon.
It does not matter how far away a photon is from the black hole, it is still influenced by gravity even if it is on the other side of the universe.
Look again at the above links and the gravitational lensing of a quasar behind a galaxy. That's an example of a lens about 2 million light years across, and their are bigger examples.
Gravities obeys an inverse square law. So gravity has an omnipotent effect throughout the universe. The noted acception to this rule appears to be the accellerated expansion of the universe.
This is the same as a black hole horizon or a spacecraft in orbit.
If the spacecraft has enough velocity, it will escape earth's gravity, else it will eventually leak gravity waves and fall back to earth. Once it has escaped the gravity of the earth, it requires even more energy to escape the sun's gravity and leave the solar system.
In a black hole, light (meaning all EMR) either has enough velocity to escape the black hole or more correctly, accelleration due to gravity is great enough to overcome the velocity of a photon.
Now once a photon has escaped, it travels at the speed of light forever.
It's not just the mass of the black hole it has to escape, it's also the mass of the whole galaxy. Like the space craft leaving the solar system.
The BIG one is escaping the entire universe. Either the entrie mass of the universe is enough to slow this photon and capture it and pull it (and everything else) back. A big crunch is the result.
We used to think that this would not happen, and that the mass of the entire universe was not enough big enough to slow it down enough.
When we measured the velocity of objects in the universe, we could then measure how much they were slowing down and thus determine the mass of the universe and if and when a big crunch would happen.
Much to our disgust, we discovered that things were not slowing down, they were speeding up ! The further away something was, the faster it was moving. This was indicative of a big bang, that formed the universe.
But we noticed that matter was moving faster than it should be.
If the universe was oscillating, the matter would appear to be slower than a linear model. If it was coasting (expanding forever) it would be linear. The observations are not linear and the curve is representative of an accellerating universe. You're second event horizon is about 13.5 Billion light years in that -> direction.
Have you bought that book yet tytower ?
I'm gunna get on your case about it. At least drag your arse down to the book shop and have a look at it. The local library will also have a copy if you can't afford the $14 for the book.
The first one is the harder read, the second one is kindergarten cosmology and very well written. We're going to make a quantum physist out of you yet !
Tanks to Kaza, he posted a link in a chat box somewhere and I picked up on it. Some good animations in this one.
Most of the animations are correct, one or two are a little dodgy. Some need an explination because it might not be apparent what your looking at.
The one with the black hole reprsented with a 3D gradient on a 2 dimensional simulation isn't what I consider to be a good look. The coalescing black holes could be a little better.... it was oversimplified and again not a very good representation.
The rest of them were good, or at least good enough. A black hole ripping a star appart also wan't quite correct, but it does give a very good basic view of a star being ripped apart long before it gets close in to the black hole.
This one is a simulation of a small black hole, something like a neutron star that is sucking matter from it's companion star. The companion eventually goes nova when its own mass can no longer hold it together.
The result then becomes a nebuala, with a white dawrf orbiting a small black hole. If the black hole cannot get enough material to sustain it, it will eventually evaporate.
another good one
With the amout of matter that seems missing to the astronomer at the time that he want to lookfor it, it seems that we cannot make true mathematical conclusions that the universe is indeed expanding for ....egs......don't we use the slingshot systems itself with space crafts....we accalerate it with... gravity......and in comaprison with all the oter objects in space.....that seems not there...or missing..i think that idea should be rethought....
If u have a black hole pressed together tightly enough ...what happens....it explodes...right...making what..??....so then the explosion itself must be greater than the speed of light from witch we call it a black hole....
What would happen is u would get something like a pulsar...the frequency u pick up is a blach hole constantly exploding and re-compressing from the same amount of mass in a bigger space pulling together just to explode again....
so then....space itself is either expanding or compressing at various parts of the universe...look in one direction and it could be expanding....in another direction....its shrinking....so on the "outer rim of space" it could always be expanding,....or itcould be compressing....depends on the overall status.
Hi every1,
This M51 collision (which it most certainly is - not an artefact of perspective) poses many good questions in Physics. The first and most interesting question posed concerns the spiral shape of very old galaxies...
This was the main reason that the dark matter hypothesis came into being! Without any other gravitational influence galaxies should be amorphous and diffuse by now...so some other influence outside the galaxy is maintaing the order...it is postulated that up to 90% of matter in galaxies is dark matter and the vast majority is in a halo around the galaxy...
Secondly, it is by no means clear that the *bigger* galaxy is attracting matter from the *smaller* one. If there was a large black hole at the centre of the *smaller* one...it would be consuming the spiral galaxy and the visible part of the lesser galaxy would be an accretion disk. However it looks globular so it is probably a more simple gravitational interaction.
Finally...we better get that Hubble replacement up there soon...I'd miss pix like these!
Ain't astro fun?
Cheers,
Kevin.
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