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Furthest Gamma-Ray Burst Ever Observed
jd writes "The SWIFT team have announced the furthest-ever observed super-massive gamma-ray burst (from 13 billion light years away). The burst was observed on the 6th of September and lasted for 3 minutes - long enough for a number of other telescopes to home in on the gigantic explosion. The distance is only barely within the reaches of the observable universe. The idea of the SWIFT telescope and follow-up observations is that they will discover both the cause of the bursts and the consequences to the star."
Imagine there are a few people rather lost at the headline (we're not all astronomers/cosmologists/whatever :) ). Anyway, NOVA ran an excellent show on this a couple years ago, and as usual there was an excellent companion website.
/I feel like a Karma whore linking to wikipedia, mod me as you see fit..
If that doesn't answer your questions, well... there's always Wikipedia.
How do we know the universe is 13.7 billion years old? It was recently discovered that the universe's expansion is accelerating as time goes by. Assuming this change in acceleration has been the case all along, doesn't that really fudge with the numbers we used to estimate the universe's age?
There are many ways to estimate the age of the universe, not all of which involve calculating the expansion of the universe.
http://www.astro.ucla.edu/~wright/age.html
What?
When supernovae occur you can see them. Are they the brightest visible object?
Galaxies are the brightest visable objects. Well, actually quasars are, but are thought to be galaxies or at least closely related to them. But the total energy put out by gamma bursts is far larger than the energy put out by supernova. It is just that they do it over a wider area of the spectrum such that their visible light component is roughly comparable to supernova but beat them by far in higher-energy radiation.
Table-ized A.I.
Well, the leading idea about (this type of) gamma ray burst says that they're associated with supernovas. So, they look like supernovas.
Quasars are the most luminous long-lived light sources. Gamma ray bursts can release more energy for short periods of time, but there are arguments about to what extent the energy is beamed in a preferred direction (complicating efforts to calculate total energy released).
I'm not sure what you mean by "alpha and beta?" Are you talking about alpha and beta radiation? Apples and oranges, although all are called "radiation". Gamma rays are a form of light (very high energy photons), while alpha and beta radiation isn't electromagnetic radiation at all, but rather particles (He nuclei and electrons).
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
For being so feisty, are you quite sure there's no such thing as alpha and beta radiation?
http://www.orau.gov/reacts/alpha.htm
http://www.orau.gov/reacts/beta.htm
Both are particle radiation and both plentifully originate in stars. You can read more about them in Wikipedia also.
http://en.wikipedia.org/wiki/Particle_radiation
ahem. Farthest Gamma-Ray... Farthest . 'Further' is a definition of degree. 'Farther' is a measure of distance.
Someone or another asks something like this everytime anything related to black holes comes up on Slashdot.
The radiation emitted from black hole related events, such as quasars, gamma ray bursts, and Hawking radiation, for that matter, comes from processes near-sometimes very near, but still OUTSIDE, the event horizon. As long as you're outside the horizon, there are trajectories that escape.
As for,
Also, if a black hole was created at explosion, was this even more massive then we can see, yet the black hole swallowed up a majority of the explosion and what we see, is just a small glimpse of it?
According to the literature on very massive stars, there as mass ranges that results in the star collapsing completely into a black hole such that no significant amount of matter or radiation gets away at all.
Check out How Massive Single Stars End their Life. Figure 1 is particularly enlightening. It's a pretty math-free article, so I think anyone who's generally interested in this stuff can follow it, maybe with a bit of help from Wikipedia and Science World.
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What's your problem? Most observatories post public schedules with the times observers will be there, what instruments they're using, etc. When the papers are published, the dates and locations of the observations are recorded, and often the observers are noted (e.g., with footnotes about who was the visiting astronomer at Kitt Peak). There was already a circular that went out last week about these observations with her name on it, specifying exactly when and where she and another observer obtained the data. She was THRILLED to have her name on this.
I don't think you have a good idea about how this stuff works. If you're some sort of weird astronomer stalker local to Wyoming, let us know. We've never had a problem at our observatory other than the occasional minor accident or mountain lion, and no one is ever up there alone. The people here are few and far between, usually friendly, and usually armed.
Where are you from, because you're being weirdly paranoid?
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
No. The effects of a black hole's gravity, even a supermassive one, are rather limited. We'd need to be within a few light years to have a problem with our sun being tidally disrupted. The radiation would destroy all life on Earth long before we got close enough to have problems associated with the supermassive black hole. We'd likely be fine with a weak quasar in the Milky Way as the gas and dust in the plane would block the vast majority of its radiative output in our direction.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Light is usually defined as visible light. If you start using the term light to refer to radio waves, you'll only sound very confused.
As someone else already pointed out there is such a thing as alpha and beta radiation. I'd suggest some remedial physics classes before you discuss physics with anyone again.
AccountKiller
My understanding is there's a low-res, very wide angle gamma-ray detector that they can use to scan vast sections of the sky. If the computers see anything interesting, they spin the probe to get a better look. If it's still a strong candidate, it then notifies anything and everything on Earth that is interested in such events.
The problem used to be that, precisely because they had to book telescopes and because telescopes are rather unwieldy, even if they saw something, it was too late to get an accurate enough fix to see what the cause was.
SWIFT was designed to solve this problem. In fact, it has discovered far more bursts than the astronomers were expecting and it started detecting them far sooner. (They got half-drowned in notifications, during the test and burn-in phase.)
So far, it has been an outstanding success - second only to Hubble, in the sense that Hubble generates better pics for the press and the average space geek. As far as I know, SWIFT was not designed to really record much in the way of actual hard data (other than location), it was more an early-warning system for giant space explosions. That is partly how it works so fast, but with the pitfall that it means that you HAVE to have additional telescopes available, if it does detect something.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
You're thinking "hand grenade in a vacuum." There was no space-time before the Big Bang, that's what it created. We're not racing away from everything, the space-time between us is spreading out. The two-dimensional analogy used in Sphereland is that of the universe being the surface of a balloon that's being inflated.
This is why the cosmic background radiation, which is a relic from the Big Bang, is visible in all directions with the same intensity.
Any object at the edge of the observable Universe would appear to be travelling away from us at the speed of light. Which basically means, we'd never see it. (The red-shift would be infinite, amongst other things.) That's not quite the definition of the observable Universe, but it'll do.
Anything marginally closer will be visible, but because there is an ever-increasing gap, the closer it is to the edge, the longer it'll take to see. (This is because although light travels at a fixed velocity, it is space that is expanding and therefore there is more distance to travel through.)
In fact, your question works rather better in reverse. Given the speed implied by the red-shift, can you calculate the fantastic distances that must be involved? The answer is yes, provided you can eliminate (or allow for) any unknowns.
For objects that have a well-defined spectral output and luminosity, it's easy. You simply compare what you see with what you should see. The shift in frequency and the reduction in output observed can both be used to guesstimate a distance.
For objects of an intermediate distance, it's harder. There are gravitational lenses, which can make objects appear further away. They're often not close enough to other objects to be able to measure an unknown against a known. Those tend to be tougher.
The further an object is, the less important lensing is, as you'd have to bend light more to add enough distance to be significant. By the time you get to 13 billion light-years, the lens would be so bloody obvious in its own right, you'd have probably spotted it first and allowed for it.
However, you can't verify calculations at all easily. At those sorts of distances, you're talking about phenomena that astronomers don't fully comprehend and cannot, therefore, tell what the profile would normally look like.
That is one reason it is important to get a good look with as many types of telescope as possible, so that we can see what created the gamma-bursts, or whatever. That way, we can verify our calculations.
(This is actually important - strange things can happen when you don't verify data. Superluminal motion, stars older than the Universe - all have been observed, but usually because of incorrect calculations or incorrect assumptions.)
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
The way we figure the distance to the furthest objects (in the 1 - 14 billion light-year range) is precisely by the rate of retreat of the astronomical objects we observe. It was noted empirically (back in the 1920's, I think) that the further away an object is from us, the faster it is retreating, in roughly linear proportion. The rate of retreat is figured out by how much the object's spectra shifts (due to the Doppler effect). So yes, some very far away objects are retreating at speeds damned near the speed of light.
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Originally, when Einstein came up with his field equations in General Relativity (1915?), they did not have a steady state solution; but an expanding universe WAS a possible solution. Apparently, this disturbed Einstein so much that he threw in a "fudge factor" called the cosmological constant, in just such a way that a steady state solution existed for the general configuration of the universe. Of course, as more and more observations poured in indicating that virtually ALL extra-galactic objects were retreating away from us, with higher speeds the further away, it became clear that the Universe was, in fact, expanding, despite the tastes of Einstein. He removed the mathematically ugly constant, and I think he later said that messing up his original equation with it was the "greatest mistake of my life."
Of course, you may wonder how we figured out how far some objects were to begin with to USE our distance = (constant) x speed formula. This post is getting a bit long, but it turns out that supernova, explosions of very massive stars at the end of their lives, tend to have an absolute maximum brightness that has a simple relationship to the length of time they "explode". Thus, supernovae can serve as a yardstick if we can spot them in other galaxies; and fortunately, they are bright enough so that we can - I think they are the ONLY individual stars we can discern in other galaxies; all the others are just too dim from those distances....
And how do we determine how far away the "first" supernova is? In other words, how did we calibrate that yardstick? Here I'm not sure; we haven't had a supernova go off close by (meaning, in our galaxy) in the last 500 years (and that's a GOOD thing - a supernova can shine as brightly as an entire galaxy at its peak! There was one in one of the Magellanic clouds (a pair of small, neighborhood galaxes) in 1987, I think); I know we have other yardsticks from direct parallax measurements (measuring the shift of nearer stars vs. their further cousins as the Earth shifts its position around the sun - good out to about 1000 light years now, I think), our knowledge of the absolute brightness to temperature as revealed by spectrum/color of stars on the main sequence, and some knowledge of the brightness patterns of ordinary novae...
There is a really good book called Parallax, which goes into the whole history of how we figured out how far away stuff in the Universe is - it's a fascinating, wonderful read; here is the amazon URL:
http://www.amazon.com/exec/obidos/tg/detail/-/080
Hope this helps.
Of course, you may wonder how we figured out how far some objects were to begin with to USE our distance = (constant) x speed formula. This post is getting a bit long, but it turns out that supernova, explosions of very massive stars at the end of their lives, tend to have an absolute maximum brightness that has a simple relationship to the length of time they "explode". Thus, supernovae can serve as a yardstick if we can spot them in other galaxies; and fortunately, they are bright enough so that we can - I think they are the ONLY individual stars we can discern in other galaxies; all the others are just too dim from those distances....
Specifically, we talk about Type A supernovae, which always have the same intrinsic brightness.
Type A supernovae are what happen when a neutron star is drawing matter from (feeding from) a companion normal star, usually in the main sequence. As it collects matter, it gets to a certain point and explodes. Usually, both of the stars survive, with the companion being somewhat less massive afterward. :)
The reason Type A supernovae are always the same brightness is that it always takes the same amount of matter for the neutron star to reach critical mass.
We can tell the distance for Type A supernovae by observing one occurring near a Cepheid variable star (and thus relatively nearby).
Cepheids are stars whose variability (the rate at which it dims and brightens) is directly related to its luminosity. So by looking at a Cepheid's variability, we can calculate how intrinsically bright it is. If a Type A supernova occurs near a known Cepheid, we can use the supernova's brightness to refine our calculations of how far other Type As are. And so we have two linked "Standard Candles" for the universe, one for relatively short distances and one for the rest of the universe.
Hope this helps. :)
Only some particle radiation (beta, I think), and high-energy E.M. radiation (UV and above), has a more than miniscule probability of doing that.
All particle radiation has that effect, and it's actually weakest in beta radiation. Alpha radiation is a lot more destructive (four nucleons instead of one electron!) but can be shielded much easier, exactly because it interacts more readily with matter. I think Neutrons are the worst, because they can activate (make radioactive) atoms they hit.
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Swift (not an acronym, so don't capitalize all of the letters) does have a wide field of view gamma-ray telescope. The interesting thing is that it also has a narrow field of view x-ray telescope, as well as a narrow field of view UV/optical telescope on board. This allows the wide field of view instrument to find the burst, then have the telescope slew to position to observe it with the x-ray and UV/optical scopes.
you have the wrong idea of "the center of the Universe". that's a meaningless phrase. We are at the center of our observable universe, but the universe as a whole is expanding, and you could call any body you wish the "center", and if you were located there you would see the rest of the universe moving away from you.
Neutrons are the worst type of radiation for several reasons.
They are neutral in charge so they tend to pass though mater and magnetic fields easily, which makes them hard to shield.
They tend to be sent out at high energy's so they tend to create lots of ions along their travel path before they slow down enough to be absorbed. These ions tend to do significant cellular damage.
When they are finally absorbed they tend to create an unstable element which will decay and emit more radiation possibly some other type of radiation and possibly more Neutrons.
The cosmic microwave backgroud radiation is the closest to seeing the big bang as we can get. Up to a certain early point in the universe's history, the entire universe was effectively opaque, though glowing brightly with its own heat. At some point the universe expanded enough to become transparant, and the light of that moment is visible in every direction all the time, as weak microwave radiation.
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That's probably the case for the short duration bursts (there was one like this identified in April -- there's probably a NASA press release you cna find about it). The long-duration bursts like this one at z=6.3 have been associated with a type of supernova.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)