Gamma Ray Burst Visible At Record Distance 68
Invisible Pink Unicorn writes "A gamma ray burst detected on March 19 by NASA's Swift satellite has set a new record for the most distant object that could be seen with the naked eye. The burst had a measured redshift of 0.94, meaning the explosion took place 7.5 billion years ago. The optical afterglow from heated gas was 2.5 million times more luminous than the most luminous supernova ever recorded, making it the most intrinsically bright object ever observed by humans in the universe. The previous most distant object visible to the naked eye is the nearby galaxy M33, a relatively short 2.9 million light years from Earth."
To put that in perspective- (Score:4, Interesting)
Re:To put that in perspective- (Score:5, Funny)
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Re:To put that in perspective- (Score:4, Funny)
Re:To put that in perspective- (Score:5, Funny)
Fixed that for you.
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If only he could somehow make his beard into a boat-like shape, flip it over, and then huddle pairs of animals underneath... Norris Ark (upside down) would save all the animals...
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Without the red shift... (Score:3, Interesting)
Ouch indeed. (I'm sure somebody will check your math and adjust the distance if necessary. So let's go with the premise of a solar input's worth from nearby.)
At that sort of distance the red shift would be virtually nonexistent. A kilowatt per square meter of gamma rays would make you toasty warm all the way through, not just on the skin.
Also: Goodbye DNA and RNA. Presuming you're still aliv
Re:Without the red shift... (Score:4, Informative)
I do not have much information, but assuming that the brightest recorded supernova emitted about 10^45 J of energy in about one hundred days (you can fetch a nice paper on this here [arxiv.org]) and this phenomenon is supposed to be two and half million times brighter for about thirty seconds (here [wikipedia.org]), I ended up with 2.5*10^6 * 10^45 * (30 / (86400 * 100)) = ~9*10^45 W of peak apparent power output of an isotropic radiation source (as in the effective radiated power for a transmitter, not the transmitter power output, in the telecommunication systems parlance - my EE education shows up ;-)).
Given that the solar constant is somewhere around 1370 watts per square meter, the distance for the irradiation to match the one we are receiving from the Sun would be about 23 kpc. This is a ridiculous number! Either I am a way off and missing something important (I am no astronomer, I admit that), or it is just that this thing could be *much* further away than those 2700 ly mentioned by the parent and it would still have enough energy to kill us all. I really do not want to imagine what would happen to us at the distance of just ~1 kpc.
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Incredible Hulk Joke Thread (Score:1, Offtopic)
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Phew (Score:3, Interesting)
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Photoshop (Score:3, Funny)
Oblig... (Score:2, Insightful)
(kisses karma goodbye)
They're shooting at us (Score:3, Funny)
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But... according to the summary: "the explosion took place 7.5 billion years ago"
And in order for our offensive behaviours to get to the aliens, we would have to give time for our message to get there. So really, what the hell did you people do to piss them off 15 billion years ago?!
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Title slightly in error (Score:4, Informative)
Anyway, it's a good thing that this occurred so far away, instead of nearby. There are a few hypergiant stars known to exist in our galaxy like Eta Carinae and the Pistol Star which are inherently unstable. And in 2004 a GRB was emitted by a magnetar half way across the galaxy that, were it visible, would have been brighter than a full moon. Its been proposed that GRB's may be a factor in past extinction events here on earth.
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It's not the gamma rays they're talking about, but the afterglow caused by gas heated by the gamma rays, and this afterglow is partly in the visible spectrum, and was in fact visible with the naked eye (magnitude between 5 and 6, which is at the edge of unaided human vision). The title is completely correct.
"No other known object or type of exp
Holland quote - issue (Score:2)
"No other known object or type of explosion could be seen by the naked eye at such an immense distance," said Swift science team member Stephen Holland of Goddard. "If someone just happened to be looking at the right place at the right time, they saw the most distant object ever seen by human eyes without optical aid."
There is no way of knowing what past humans eyes have seen. There may have been a more distant object at some time in our past that was viewed by human eyes, just not recorded.
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Thus the disclaimer of "No other known object".
Re:Title slightly in error, except that it's not. (Score:2)
Record Distance (Score:5, Funny)
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Because a particular object or event such as a GRB has a known "color" to compare it with. How do they know? Through combining what they know about physics and observational data.
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When you pass the light from a star through prism you don't get a continuous band, there's light and dark lines in the spectrum.
The light and dark lines correspond to absorption and emission energies of different elements in different quantum states.
see http://en.wikipedia.org/wiki/Emission_spectrum [wikipedia.org] and http://en.wikipedia.org/wiki/Doppler_shift [wikipedia.org] for more info.
Article is wrong (Score:2)
> Later that evening, the Very Large Telescope in Chile and the Hobby-Eberly Telescope in Texas measured the burst's redshift at 0.94. A redshift is a measure of the distance to an object. A redshift of 0.94 translates into a distance of 7.5 billion light years, meaning the explosion took place 7.5 billion years ago, a time when the universe was less than half its current age and Earth had yet to form. This is more than halfway across the visible universe
This contains some serious misund
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http://www.space.com/scienceastronomy/mystery_monday_040524.html [space.com]
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Don't believe anything not in song (Score:5, Funny)
That's orbiting at nineteen miles a second, so it's reckoned, a Sun that is the source of all our power.
The Sun and you and me and all the stars that we can see, are moving at a million miles a day, In an outer-spiral arm at forty-thousand miles an hour, of the Galaxy we call the Milky Way.
Our galaxy itself contains a hundred-billion stars, it's a hundred thousand lightyears side to side.
It bulges in the middle, sixteen-thousand lightyears thick, but out by us it's just three-thousand lightyears wide.
We're thirty thousand lightyears from Galactic central point, we go round every two-hundred-million years.
And our Galaxy is only one of millions of billion in this amazing and expanding Universe The Universe itself keeps on expanding and expanding in all of the directions it can whizz. As fast as it can go, the speed of light you know, twelve-million miles a minute and that's the fastest speed there is.
So remember when you're feeling very small and insecure how amazing unlikely is your birth. And pray that there's intelligent life somewhere out in space, 'cos there's buger all down here on Earth!
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> As fast as it can go, the speed of light you know, twelve-million miles a minute and that's the fastest speed there is.
That's actually quite wrong. We can see stars with a redshift of 6.3, meaning that it is moving away from us at 21 million miles a minute (compared to the 12 million miles a minute for the speed of light).
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If you assume that we are a stationary object and also assuming that space is flat. We know that both of those are incorrect. We are not stationary in space and space is not flat but a function of space-time. The earth may have a calculable velocity within our own space-time environment but the redshift of 6.3 which could attribute a perceived velocity of 21 million miles per minute is still less th
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No, if you assume that we are a stationary object and that space is flat, then an object with a redshift of 6.3 would mean that it is moving away at 6.3 * speed of light = 70 million miles a minute. The 21 million miles a minute takes into account the curvature etc.
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But the universe is younger than that, so how
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Which would seem to mean it's expanding faster then light, the universal speed limit...
Okay, *now* my head hurts.
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I still don't see why that would allow it to violate the speed of light anyway (certainly not more then 2x).
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If you define a light year as the distance light travels in a vacuum in a year, then the article is consistent. I don't think astronomers really use light years as a measurement for cosmological distances for that very reason. But the general public thinks they know what a light year is, so press releases have to tr
Re:Article is wrong (Score:4, Informative)
Your definition would be what cosmologists call 'comoving distance'. I have never seen a light year defined in this way however. The rate of expansion changes with time, so under your definition you would end up with things like that 2 * 1 light year != 2 light years, etc.
It also means that a light year now, would be a different distance (in km) than a light year was a year ago, etc.
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Reading the (two) articles, the distance measure actually only appears in that one paragraph in the press release. Everywhere else they seem to just give the travel time. On the other hand, I plugged 0.94 into a redshift calculator and it spit out 2.38 Gpc, which would agree with the 7.5
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I emailed the author, and they have now corrected the article.
The article now just says:
The explosion was so far away that it took its light 7,500,000,000 (7.5 billion) years to reach Earth! In fact, the explosion took place so long ago that Earth had not yet come into existence.
And the title has also been changed to "A Stellar Explosion You Could See on Earth!" (Instead it was something about that it happened half way across the universe from us)
Re:Article is wrong (Score:5, Informative)
Hi John,
Thanks for your message. I was the principle author of the press release, so I will try to answer your question. I should note that the press release was reviewed by numerous scientists. But it was edited at NASA headquarters before it was made public.
In my original draft, I purposefully avoided making the statement that the GRB was 7.5 billion light-years from Earth, because as your message implies, it is problematic to express specific distances when one is talking about events that happened in the very distant past, because the universe is rapidly expanding. Such is the case when trying to express a "distance" to GRB 080319B.
The most relevant direct "distance" measurement is the object's redshift, which was measured to be 0.94. As the press release explained, this measurement tells astronomers how much the GRB's light was "stretched" by cosmic expansion. I used this popular website from a renowned UCLA cosmologist to convert the object's redshift to a light-travel time:
http://www.astro.ucla.edu/~wright/CosmoCalc.html [ucla.edu]
When I entered the redshift and the cosmological parameters based on the latest results from the WMAP satellite and large-scale galaxy surveys, the calculator gave me a light-travel time of 7.5 billion years. In other words, the light from this GRB was emitted 7.5 billion years ago.
But at the time the burst occurred, Earth didn't even exist, so how does one express a "distance" between one object and another object that does not exist? In addition, 7.5 billion years ago, the visible universe was a much smaller place than it is now, because cosmic expansion has made the universe much bigger during those intervening 7.5 billion years. The GRB's host galaxy and the Milky Way Galaxy would have been much closer back then than they are today (please note that the Milky Way would have been a lot different back then, but it undoubtedly existed at that time). In fact, back then, the two galaxies would have been much closer than 7.5 billion light-years. And yet because of cosmic expansion, the two galaxies are currently much farther apart than 7.5 billion light-years. So there really is not an ideal way to express such a huge distance.
In my opinion, the best way to express such a huge distance in a rapidly expanding universe at the level of a popular audience is to express distances in terms of light-travel time, which is what I did in the original draft of the press release. And because our best current measurements suggest that the universe is 13.7 billion years old, an event taking place 7.5 billion years ago is roughly halfway across the visible universe. Some of the scientists at NASA probably felt that it was important to specify a distance in a unit of distance rather than in a unit of time, so they translated the light travel time to a distance in light-years. I realize this is imprecise from a strict scientific perspective, but the NASA scientists concluded that there is no better way to express it, and I cannot think of a better way to do it.
The problem, of course, is that the most precise way to express the distance is to state the redshift, which I did in the press release. Unfortunately, the term "redshift" has little meaning to the media and public, and the general public does not have the familiarity with astronomical terminology to be able to translate a redshift of 0.94 into a distance that has any deep meaning.
Best regards,
Robert Naeye, NASA Goddard Space Flight Center
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It's all because of A. C. Clarke's death (Score:3, Interesting)
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Obligatory Monty Python quote: (Score:2)
*maniacal laughter*