GammarayBurst observatory nears launch

[Martin]

NASA article dated 24 January about GRB, includes some animation

http://science.nasa.gov/headlines/y2008/24jan_glast.htm?list45222

 

GammarayBurst astronomy is featured in the agency's news because the satellite instrument GLAST is scheduled for launch the first half of this year. Currently the launchdate is set for 16 May.

 

Here's a GLAST webpage

http://glast.gsfc.nasa.gov/

 

As the animation in that 24 January article shows a gammarayburst can take only 5-10 seconds, with the main peak coming in a spike that lasts only one or two seconds. Nobody knows the mechanism---some kind of star explosion that differs from supernova.

 

On the other hand GRB oftentimes come from several billion LY. The light from them can have been traveling over a billion years by the time it gets to us.

 

One thing GLAST will permit to do is to check for energy-dependence in the speed of light. If the more energetic photons in the delayed by as much as a second, after traveling for a billion years, as compared with the less energetic photons in the flash, then it should be possible to detect this energy-dependent delay.

 

Some observations last year suggested that there might be such a delay. I don't think it is very likely, most probably it was just a fluke thing in their data or a delay in emission at the source, but if it does check out with GLAST this would shake the theorists up bigtime. Light is all supposed to travel at the same speed regardless of the energy of the photon.

 

Maybe the most important thing GLAST will do is get enough data on GRB so people can figure out what causes these huge explosions. Supernova mechanisms are fairly well worked out----these flashes are brighter than supernovae and seem to involve the release of more energy, unless something is beaming them and we happen to be inline with the beam. The flashes are so little understood that it is likely the explanation when we finally get it will be quite interesting.

 

Hopefully they'll make the 16 May lauchdate.

[Martin]

http://glast.gsfc.nasa.gov/

 

The first stage (Delta II rocket) arrived at Cape two weeks ago.

Now both stages one and two are on site.

 

The launch is still scheduled for 16 May.

 

GLAST (gammary large area space telescope) is designed to watch the celestial fireworks caused by stellar collapse and flares from cores of galaxies. The light from these things does not get down thru our atmosphere because the photons interact with air.

 

GLAST is meant to see photons with up to 300 GeV (about one third of a trillion electron volts).

 

It is intended to study events involving higher energies than we can produce artificially with accelerators on the ground.