At Last - GLAST!

by Clifford Johnson     Department: Space

Good news everyone! GLAST has been launched successfully. GLAST stands for Gamma-ray Large Area Space Telescope, and it does exactly what it says on the packet. It is an instrument designed to look more closely at gamma rays from outer space. More here. It will help (alongside other instruments such as SWIFT) get better understanding of a wide range of gamma-ray emitting objects, that pertain to a wide range of issues, astrophysical to cosmological.

"Gamma ray bursters" are obvious super-powerful sources of gamma rays out there, largely due to macroscopic astrophysical objects (collapsed stars or stars in the process of doing so, or merging with each other - see earlier posts) doing violent things, or interacting violently with their surroundings. So are active galactic nuclei, powered by black holes. We'd like to better understand all of the processes that allow these objects to generate gamma rays.

Other sources could include particles and antiparticles annihilating each other and (by conservation of energy and, yes, E=mc²) producing gamma rays. (By the way, a nice thing about this is the fact that GLAST detects gamma rays by the reverse of this very process. A gamma ray arrives on the metal of the detector (the "Large Area" part of the name) and produces particle-antiparticle pairs which are measured in the electronics.) It would be great to get handle on more of these types of "particle astrophysics" processes out in space. This sort of thing can happen for not just ordinary matter, but also unusual forms of matter such as whatever it is that makes up dark matter (which as you know, makes up over 80% of the matter in the universe). In this way we might get more clues as to what most of the matter in the universe is actually made of.

GLAST might also give us insights into other things as well. These are high energy photons travelling over large - cosmological - distance scales. Some theorists speculate that if there is anything to be learned about subtle properties of spacetime that might affect propagation through it ("dispersive" properties - this is like how you can learn about properties of a piece of glass by seeing what it does to light that passes through it) then this could be a place to look. (It's got to be really subtle since we've not noticed it in any other physics so far, and such dispersion is hard to reconcile with lots of other physics we know to be correct... But it never hurts to check to see that that which you think you understand is actually working properly out there in the real world.)

Anyway, you can learn a lot more about the launch from a number of places, including of course the mission pages here. Paul Rincon at the BC has a piece here. Loretta Hidalgo Whitesides at WIRED has a nice article too. She spends an unusual amount of the article explaining the etymology of the name "Delta II 7920H-10", the type of rocket used for the launch, so you should rush over there to find out. There's a nice article (from 2006) by Heather Rock Woods in Symmetry about the science goals.

-cvj

(*Cross-posted to Asymptotia)

Tags: gamma rays, GLAST