Uploaded April 2012 | Updated September 2026, 2 weeks ago
The Large Area Telescope (LAT) detects gamma rays by using Einstein's famous equation (E=mc(squared)) in a technique known as pair production. When a gamma ray, which is pure energy, slams into a layer of tungsten in one of the Tracker's towers, it can create a pair of subatomic particles (an electron and its antimatter counterpart, a positron). The direction of the incoming gamma ray is determined by projecting the direction of these particles back to their source using several layers of high-precision silicon tracking detectors. A separate detector, called a calorimeter, absorbs and measures the energy of the particles. Working on gamma ray at a time, the LAT will make gamma-ray images of astronomical objects, while also determining the energy for each detected gamma ray.
This animation shows a gamma ray (purple) entering a corner tower of the Tracker. After the electron (red) and positron (blue) cascade down the tower, their incoming paths (red/blue) combine to show the original path (purple) of the incoming gamma ray that created them.
Animation Number: 20122
Completed: 2007-09-12
Animator: Chris Meaney (HTSI) (Lead)
Scientist: Steven Ritz (NASA/GSFC)
Platforms/Sensors/Data Sets: Fermi/LAT
Fermi
Series: GLAST Pre-Launch
Astrophysics Animations
Credit: NASA/Goddard Space Flight Center Conceptual Image Lab
The Large Area Telescope (LAT) detects gamma rays by using Einstein's famous equation (E=mc(squared)) in a technique known as pair production. When a gamma ray, which is pure energy, slams into a layer of tungsten in one of the Tracker's towers, it can create a pair of subatomic particles (an electron and its antimatter counterpart, a positron). The direction of the incoming gamma ray is determined by projecting the direction of these particles back to their source using several layers of high-precision silicon tracking detectors. A separate detector, called a calorimeter, absorbs and measures the energy of the particles. Working on gamma ray at a time, the LAT will make gamma-ray images of astronomical objects, while also determining the energy for each detected gamma ray.
This animation shows a gamma ray (purple) entering a corner tower of the Tracker. After the electron (red) and positron (blue) cascade down the tower, their incoming paths (red/blue) combine to show the original path (purple) of the incoming gamma ray that created them.
Animation Number: 20122
Completed: 2007-09-12
Animator: Chris Meaney (HTSI) (Lead)
Scientist: Steven Ritz (NASA/GSFC)
Platforms/Sensors/Data Sets: Fermi/LAT
Fermi
Series: GLAST Pre-Launch
Astrophysics Animations
Credit: NASA/Goddard Space Flight Center Conceptual Image Lab
