Talk:GRB 080319B

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Help with this template Comments: edit – history – watch – refresh This article is a very good stub and could have been rated start-class in relation to the expectations of its topic. To expand it significantly from where it is now, we need to wait for more reports to surface. -- Sverdrup (talk) 16:55, 23 March 2008 (UTC)

[edit] Visibility

Is this is still visible to the naked eye? Please respond. Camilo Sanchez (talk) 22:23, 21 March 2008 (UTC)

No. The theoretical visibility lasted 30 seconds. ^[1] --Spischot (talk) 22:54, 21 March 2008 (UTC)

No. Even with binoculars (Mv < 9) you had < 60 seconds, with naked eye (Mv < 6) < 30 seconds. The peak was dimmer than Mv > 5. (See the light curve: http://vo.astronet.ru/~karpov/grb080319b_lc_10.gif ) Macchess (talk) 18:42, 23 March 2008 (UTC)

[edit] Distance?

The GRB's red shift was measured to be 0.94 which translates to a distance of 7.5 billion lightyears.

Is that the distance to the object when the explosion occurred, or the present distance to the spot where the explosion occurred, or the distance that the light had to travel to reach us? In an expanding universe those three distances would be different. When did the explosion occur? AxelBoldt (talk) 22:53, 21 March 2008 (UTC)

I think you are right, but [1] actually said the distance was 7.5 Bly when I quoted it for the first time, but later changed that. [2] still says that's the distance. -- Sverdrup (talk) 04:17, 23 March 2008 (UTC)

I don't understand the "I think you are right" part-- it was just a question, not a statement. But your NASA link seems to clarify the situation: it took the light 7.5 billion years to get here. AxelBoldt (talk) 17:20, 23 March 2008 (UTC)

Your question is ill-formed. Elapsed time can be defined different ways depending on whether you are talking standard or relativistic. There is no semantically meaningful way to discuss the "present distance" to a spot that is 7.5 billion light years away; distance and time are irrevocably intermingled in the equations and the velocity at which the interval is traversed changes the answer. 75.15.140.162 (talk) 06:06, 23 March 2008 (UTC)

That is incorrect. In a homogeneous expanding universe model with a big bang, you can define a universal unique time at all positions. You imagine a huge set of identical clocks emerging from the big bang that initially all show the same clock time, and then each clock follows the expansion. If you want to know what time it is right here right now, you look at the clock that made it here. "Present distance" then means that you consider that slice of spacetime where all clocks show the same time as my local clock, and you measure distance in that slice. It's explained in Wald's Relativity book. Of course the final answer for the distance will depend on the cosmic model you choose; the only unambiguous quantity is the red shift. AxelBoldt (talk) 17:20, 23 March 2008 (UTC)

This is much harder than I had imagined. The current state of cosmology is confusion (certainly for me at least). Most of our articles seem to accept that the time it took for light to get here (time since the event) gives the corresponding distance in lightyears. The NASA article seems to deliberately express it in time, but I swear the first time I read the same URL (first time dated 20 march, now 21 march, see wiki page history), they put it in distance too. -- Sverdrup (talk) 17:26, 23 March 2008 (UTC)

Verry intresting since the universe mass distribution wasnt always homogeneous in the beginning (as a simple proof check the distribution of stars they folow clusters) so time might not be evenly distributed. Indeed all clocks have a certain same moment, but since mass distribution isn't equal troughout space it would bands space-time, perhaps not be that big (altough if it is slightly then what if this effecs happened many million of years??) It's even worse if one would use clocks on top of a heavy object (planet sun blackhole). If a clocks alarmsound went with the speed of light. We wouldnt hear them all at once. (unless you where at the middle of it all >> to make it even worse we indeed seam to be in the middle (as expansion seen is equal in all directions unexplained yet)) altough that doesnt mean that other stars where in the middle also or (or we still should refine our possition). Well i asume redshift calculations work a bit differently not with absolute time. —Preceding unsigned comment added by 82.217.143.153 (talk) 23:04, 25 March 2008 (UTC)

[edit] Contradictions

We already had

it had a peak apparent magnitude of 5.8 and remained theoretically visible for ~30 seconds.^[2]

and then we added

The afterglow was just barely visible with the naked eye for about an hour, at a magnitude of about 5.^[3]

I interpret this as contradictory. This nytimes source is highly suspect to me, it puts everything in very vague and unscientific terms, we should not use numbers/data from it IMO. -- Sverdrup (talk) 17:26, 23 March 2008 (UTC)