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View Full Version : What speeds to Gamma Ray blasts from Large stars travel?



dirty_g
2006-Jul-30, 10:35 PM
As the title suggest I would like to know what speed these beasts of nature travel. Some suggest faster than the speed of light?? Apparently the idea that one of these bad boys caused an extincyion is a seriously entertained one in the scientific community. At least according to Astronomy Now magazine. Not that im worried about that as they are rare in our galaxy.

Ken G
2006-Jul-30, 10:40 PM
Gamma rays are a form of light, and so travel at exactly the speed of light through a vacuum. I would guess that gamma rays think most of interstellar space is a vacuum.

RussT
2006-Jul-31, 09:05 AM
First of all, lets clarify a few things here!

There are 2 types of GRB's, short ones with duration times of 2 seconds or less, and long GRB's of greater than 2 seconds in duration, that usually go 2 seconds to 500 seconds although there are 'some' that are longer than 500 seconds in duration.

The short ones are thought to be neutron star/stellar black hole related, and those are the ones you really should be refering to here. These can be in any galaxy, but as far as I know, there are none of these close enough to us to cause a problem.

Now, it is "ONLY A THEORY' that the long GRB's are caused by massive stars, now 'thought' to be in blue, very dim, star burst galaxies, and usually occur randomly about once a day throughout the entire sky (if we could watch all of the sky). I'm not sure how close the closest 'recorded' so far is (I think it is about 150 nillion light years), but they have been recorded out to some 12 + billion light years.

Here is the SWIFT GRB home page.

http://swift.sonoma.edu/about_swift/grbs.html

dirty_g
2006-Jul-31, 05:57 PM
So they actually can stretch 12 billion lightyears?

RussT
2006-Aug-01, 06:28 AM
The answer to this is actually fairly complex, but here are the basics.

When the Long GRB explodes, because of its immense power, it emits gamma rays (radiation). That is the most powerful radiation known in the universe and can come in different units of energy known and KEV, GEV, and TEV. Now, they are currently putting the long GRB's in the KEV to low GEV range, however, they could be in the high GEV to TEV range and we would not know it because high GEV and TEV energy gamma are absorbed before they can ever reach the earth (accept for maybe a few, and these may be the sources of the UHECR's (Ultra High Energy Cosmic Rays).

The bottom line though is, when the GRB explodes 12 billion light years away, that means that it took 12 billiom years for that light to reach us, and the afterglow that we can detect (when they can detect it) is still 12 billion light years away, and that would be where most of the destuctive power would be that would threaten anything.