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Plans To Peer At A Black Hole's Event Horizon
mattorb writes: "From the press release: "Scientists have designed and succesfully tested a new type of X-ray telescope that, when fully developed and placed in orbit, may capture the first images of a black hole and resolve images of nearby stars as clearly as we can see our own Sun today. The report is published in the Sept. 14 issue of Nature."
Go here for more information on the project, which is known as the Micro Arcsecond X-ray Imaging Mission. Note that the proposed MAXIM mission would launch after 2010."
...until physics gets to the point where we can truly prove that
Relativity as Einstein theorized is basically unchallenged it could be a waste of money simply to search for
black holes.
Up to now, there is no experimental evidence that GR is wrong. Theories cannot be proven to be right, they can only be disproven. Experiments can only confirm a theory or invalidate it, in the case of MAXIM, the finding of a black hole (or more precise, the finding of an event horizon) would be another confimation of GR. Consequently, you would have do define a level of confidence of GR, that you regard as sufficient to fund the search for black holes. More precise, you would have to suggest experiments suited to confirm GR, that would be prerequisite for funding black hole research. I doubt that you can find such experiments (they have to be less expensive than MAXIM) that havent already be done. After all, scientists like to pick the low hanging fruits first, as much as anyone.Black holes can be detected (in theory of course) by looking for the emissions they give off. The theory goes (extremely roughly) that as individual particles reach the "edge" (event horizon?) of the black hole (crossing this line means you never come back), some of them are torn apart, half of the particle going in, half going out, and some energy is released during this fission. It is these fissions at the edge that make a black hole appear to give off energy, and make it detectable.
That type of radiation is called Hawking Radiation (after Stephen Hawking, naturally). However, this isn't what lets us detect black holes, as Hawking Radiation is ridiculously faint. Black holes can be detected by the X-Rays that they "inadvertantly" produce. When matter is falling into a black hole it is accelerated, heated, and compressed to such a degree that it gives off large amounts of X-Rays. I believe the first black hole we detected (again, assuming black holes exist), was Cygnus X-1 (or cygnus something), and we detected it by the x-rays it gave off.
Another method of detecting black holes is to look for graviational lensing effects. Because black holes are so massive, they bend the fabric of space time. (Imagine a sheet suspended in the air. Place marbles on the sheet. The marbles make depressions on the sheet, like stars make "depressions" in space-time. A black hole is so heavy, it's like dropping something that is the size of a marble but with the weight of a bowling ball onto the sheet. The sheet bends A LOT, and it actually will have a hole where the singularity is.) Light travels in a straight line, so if space-time curves, light also curves with space-time. Gravitational lensing was proved during a solar eclipse. Astronomers observing the eclipse noted that they were able to see stars that should have been blocked by the eclipsed sun. The sun's gravitational field caused enough "lensing" so that stars directly behind the star could be seen to either side of the star. So, if we find something out in space that is causing a LARGE amount of gravitational lensing, but we can't see anything, there's a chance it's a black hole. At that point we normally observe it more to determine if it is or isn't a black hole.
The details of even the proposed pathfinder mission (I can't find any details for the main mission) are fairly mind-blowing. The pathfinder is effictively an X-ray telescope with a 450km (300 mile) focal length. This is two spacecraft flown in formation at this distance with their relative positions and angles controlled and sensed to hideous precision.
Of course pointing the telescope at a new target takes a while.
Was I the only one who read that and wondered why you'd need a peering arrangement on an event horizon?
I mean, surely your data would take longer to retrieve?
_____
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Obviously, I have something wrong. So how do mirrors that reflect X-rays work?
You're absolutely right that an X-ray photon will rip electrons (even core electons) out of an atom, and will not therefore be reflected. However, at very low angles of incidence (a few degrees at most) X-rays are reflected. (I think this is because they interact with many atoms at once, rather than just one -- quantum effects come in here, and I can't remember the details :( ). Anyway, whats this means is that you can build an 'X-ray lens' by nesting lots of carfully arranged cylinders, whose axis points in the direction you're looking. X-rays reflect off the inner surface of the cylinder onto your detector at the back of the telescope.
This isn't the only way to do it; a slightly weirder method is to put a Uniformly Redundant Array where you would normally put the lens. By selectively subtracting X-rays from the source image, this result in the detector seeing convolution of the image (like a fourier transform) which can be deconvolved to the original image. see here for an introduction to URA high energy telescopes...
URA telescopes like BLAST have the disadvantage that you reduce their sensitivity due to blocking half the incident X-rays. On the other hand, I think you can use them do detect higher energy X-rays than low-angle reflection telescopes. But someone who actually works on these things will probably contradict me :)
nosig
Exactly. I saw the headline and thought, "Gee. What are they doing, using some kind of singularity effect with really tiny black holes to make high-bandwidth FTL links for a system-wide network so that astronauts on the Mars mission can publish their findings and the AOL users can have good latency to their server?"
Oh, go on, check out my job.
Didn't they listen to their mothers? Mine always told me I could go blind if I stared too long at a black hole.
Sounds very impressive, definatly. Compared to the Hubble, it's completly next-generation. Learning the secrets to black holes may in fact lead us to faster than light travel. After all, black holes are so strong, they trap light too.
:-)
You'd have to wonder, though, if MAXIM is being planned, what's up with Chandra? Did it not live up to expectations? Has me wondering if MAXIM will too...
It brings up some very interesting possabilities, too, though... If anything, we'll at least find out where all those socks go that you swear go into the dryer, but never come out
-PhaseBurn Welcome to Linux country. On quiet nights, you can hear windows reboot.
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You see "Plans to Peer at a Black Hole's Event Horizon", and the first thought you have is "who the hell is Blackhole.com or Eventhorizon.com, what do they have to do with P2P, and why haven't I heard of them before?!?!"
Hawking radiation comes from localized fluctuations in the electromagnetic field intensity of the void. That is to say, even though on average a certain area of empty space beyond the event horizon is, say, E_0, small localized fluctuations may result in, say, differences of +/-1eV.
Now, given that photons are the carriers of the electromagnetic force, you can consider the -1 eV and +1 eV as two virtual photons. These are not a photon and an anti-photon: they're a photon of positive energy, and a virtual (i.e. whose longevity is less than Plank's time) photon of negative energy. Or, if you prefer, if you set E_0 to 10 eV, then the first photon has 11 eV, and the second 9 eV.
Now, the positive photon may have enough energy to escape the black hole's pull; the negative photon, OTOH, automatically does not. It falls into the black hole, where it anihilates with a photon caught inside.
End result: the black hole is 1 eV poorer, and a 1 eV photon has been emited by the space around the black hole. This, in effect, means energy somehow 'escaped' the black hole, and can be measured as radiation.
It's a nifty concept, but unfortunately, its intensity pales in comparison to the radiation emitted by matter falling into the black hole as it is accelerated.
The formation of galaxies is definitely a topic of major research interest; one of the major science missions of the Next Generation Space Telescope is to probe "the era when galaxies were young" (as the hokey PR material used to say). Keep in mind, though, that the problem is not just one of building a bigger telescope, but of building a telescope that is sensitive in the right wavelength regimes : the farther away from us you look (and hence the farther back in time you're probing), the more "redshifted" things become; their light is shifted to longer and longer wavelengths. So to probe the early galaxies, NGST has to be sensitive in the infrared region of the spectrum -- which brings up a whole slew of complicated design problems. (The Earth glows in the IR, for one thing, so a near-Earth orbit isn't practical -- the NGST will be nowhere near us, and hence impossible to service once it goes up.)
Everyone is talking about looking at black holes, but does anyone know if we have the ability to study the hubble horizon with the telescopes that we currently can build? What kind of research is going on concerning that swampy reigon of space where we can see galaxies forming?
Just curious...
Kan jeg få en pils, vær så snill?
I believe that link discusses the subject to which you are referring. This guy and his friend performed an experiment in which the group velocity exceeds the speed of light. As I understand it, group velocity is an idealization: it is the notion of the velocity of a pulse, not a photon. As the article explains, in some sense they've gotten the pulse to traverse a medium faster than c. But, "no object or information has been made to travel superluminally."
So, surprisingly enough, nearly seventy years' worth of physics has not been suddenly and summarily disproven.
If you're not wasted, the day is.
If you're not wasted, the day is.
I mean, come on: the second phase (100-nanoarcsecond res.) calls for keeping "up to 33" spacecraft flying in formation with a precision of 20 nanometers?!?! H-H-How? Or rather, How Much?
Is this a vapor dream, or has someone actually checked the $important numbers?
If you're not wasted, the day is.
If you're not wasted, the day is.
When pointed toward the earth, MAXIM will be able to use x-ray diffraction to produce a working "X-Ray Specs" effect which will see through people's clothes.
Is that OK?
every time something this cool happens, i get more of that wonderful "i'm living in the future" feeling.... maybe it's me, but once in a while don't you feel excited about NOW? i mean, only a few years ago black holes were just some ludicrously unprovable idea. now we're gonna LOOK at them, or at least their even horizon. neat-o.
--endcycle--
Am I the only one who notices that the government is namimg this project after a men's magazine? Or perhaps the only one who cares?
The Sacred Chao says, "MU".
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They use gold in all of the X-ray mirrors I've heard of - it is a heavy enough atom that the innermost electrons are tightly bound and the energy from X-rays only causes a transition to a higher energy level rather than ionizing it.
This page describes the manufacture of an X-ray mirror for an ESA mission. I assume they're all fairly similar.
... black holes also show up in superstring theory (well technically M-theory). You can use a D-brane to model the black hole, and this technique has been used to acheive a first principles calculation of the microscopic entropy of a black hole, whereas traditional techniques used fairly general arguments and a bit of hand-waving.
On a side note, string theory may suggest ways that information can escape from a black hole due to violations of locality. This is still very much open to debate though.
For more information, see here at the Cambridge University's Relativity pages.
I don't know how relevant this is, but we just had an article (too lazy to link, sorry) about how the speed of light barrier was broken (by light, ironically). If this is true, doesn't it shoot many physics theories down the drain? And if so, how would if affect this one?
You mean this article? It wasn't really light travelling faster than light at all, merely an effect due to the fact that the pulse of light has a leading edge which travels ahead of it. When this leading edge hit the target, the entire pulse was recreated and transmitted from the other side of the caesium target.
Whilst it looked like the speed of light barrier was broken, it wasn't really, it was just a cunning effect. Whether this effect could be used to transmit information faster than light is unknown - it depends on whether this leading edge can hold information or not.
As for tachyons, well they always travel faster than light and indeed speed up as they lose energy - a tachyon with zero energy would travel at infinite speed!
When a star collapses the matter begins to implode upon a point, eventually crossing the point where the escape velocity becomes greater than the speed of light and a black hole is formed. The edge of this black hole is what we call the event horizon - anything passing within the event horizon cannot ever escape. The simple solution is described by the Schwartzchild metric.
The matter however is still collapsing to a point at the centre of the black hole. According to general relativity there is nothing to stop this collapse and we end up with a point of infinite density and zero volume - a singularity.
However when you come to rotating black holes (described by the Kerr metric) there are differences. The angular momentum of a collapsing star is conserved, and this causes the black hole's event horizon to bulge out along the equitorial plane, much like the Earth has a slight bulge around its equator. Indeed, the central singularity itself forms a torus rather than a point when the black hole is rotating.
As angular momentum is increased this bulge gets bigger and the polar size of the event horizon shrinks, until eventually you are left without an event horizon at all, but just a torus-shaped singularity, which is said to be "naked".
Of course, whether a naked singularity can ever exist is an open question. There is something called the "Cosmic Censorship Principle" which states that the laws of physics will never allow a naked singularity to form, but the final answer is "we don't know".
Also of interest is that since the naked singularity would be in the shape of a torus you could theoretically pass through the centre of the torus and find yourself somewhere completely different, possibly even in another universe!
For a fairly technical intro to black holes and singularities, see this article at suite101.
they see a green planet with two arms and a tongue sticking out...:p
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How Jaded Are You?
A large black hole was discovered in Manchester yesterday. Authorities are looking into it.
(OT) My last interest in Black Holes was that the warping of space-time would be the method of point-to-point space travel. Unfortunately, if I were to synthesize a black hole in my kitchen the radiation would probably kill me. Any practical use for these things, other than fodder for nobel prizes?
Vote Naked 2000
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