What Happens if a Supernova's Gamma Rays Reach Earth?

[Shenstar]

Here's a question I thought about while watching one of those simplified 'the universe' documentaries on discovery channel.

If a supernova in our region of the galaxy exploded and the gamma rays from the poles of the neutron star or black hole reached us, it was mentioned it would happen too fast for us to even realize it had happened.

I just wanted an explanation as to how the speed of light factor works in such a scenario.

If the star was let's say 14 million light years away, would that mean that star exploded 14 million years ago?

And would it mean it took 14 million years for the gamma ray bursts to reach us, and if those gamma beams (forgot what they're actually called) would appear instantly to us, although have been traveling towards us for the. Last 14 million years?

 

[Eimacman]

The speed of light does not play much of a role in this scenario. It is the amount of warning the Earth would receive before the GRB arrived, like a neutrino burst that would occur just before a core collapse supernova. Therefore if neutrinos are missing before a GRB then you would not know until it was too late.

 

[Shenstar]

What would we see from Earth if this happened? As the explosion happened 14 million year ago, won't we see the gamma ray burst slowly approaching?

What I find hard to grasp is the concept of something so big traveling so fast, yet reaching us after 14 million years?

Is that correct?

 

[68658]

You wouldn't 'see' per say anything. Its like a picture is taken of a moment in time. this picture is the first of many each one carrying energy (each frame of reference so to speak). The first picture will hit you after 14 million years of being "taken". So to view it coming (it being the actual 'mass' of gamma rays and other energys) would mean you would of seen the burst befor it hit you. (Now seeing in this scenerio means when it hits you.) The only way you would know its comeing it FTL communication or measureing netrino burst and other tell tell sign comeing before th 14 million years ago, say 15 million years ago (14 light years 1 million years befor it goes supernova). On Earth everything would appear as usual until the burst travleing at light speed enters your viewing perspective.

 

[Drakkith]

What would we see from Earth if this happened? As the explosion happened 14 million year ago, won't we see the gamma ray burst slowly approaching?

What I find hard to grasp is the concept of something so big traveling so fast, yet reaching us after 14 million years?

Is that correct?

Gamma rays are merely high energy photons, AKA light. They move at the speed of light, which is the value c. Which is 186,000 miles per SECOND. An explosion that happened 14 million light years away would reach us in 14 million years. The distance between objects in space is ENORMOUS. The light from the sun takes 5 hours to reach the outermost planet, neptune, while it takes over 4 years to reach the nearest star to the sun.

No matter how "big" the explosion is, the gamma rays never travel any faster or slower than that.

 

[DavidMcC]

Shenstar, the problem with GRBs and the events associated with them is the rapidity with which their spectral intensity evolves from the moment the first part of it hits. That is why the satellite, Swift was sent up:
http://en.wikipedia.org/wiki/Gamma_ray_burst"
As the article mentions, the system is now largely robotic, to improve the response time.
So, it isn't the speed of light that's the issue, but the rate of change of the signal.

Aside: If one of these things happens in our galaxy and happens to be beamed at us, we could have more than just science to be concerned about!