How astronomers were first able to discover the lobes of the Fermi Bubbles
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Collecting gamma-ray data
The Fermi Gamma-ray Space Telescope which launched on 11 June 2008 observes light in the photon energy of between 8,000 and 300 billion electronvolts. It collected the data which astronomers Douglas Finkbeiner, Tracy Slatyer and Meng Su used during their discovery of the Fermi Bubbles.
Gamma-ray Burst Monitor
This instrument includes 12 detectors on opposite sides and facing different directions. They are made of sodium iodide to catch X-rays and low-energy gamma rays. When hit, a flash of light emits that can be detected by a photomultiplier tube. Comparing the rate of signals from different detectors determines where the rays came from.
High-energy detectors The Gamma-ray Burst Monitor also has two further detectors that are made from bismuth germanate, which catches high-energy gamma rays. Their positioning means they provide close to total full-sky coverage.
The Large Area Telescope The Large Area Telescope is comprised of four subsystems, and it works to detect and isolate gamma rays. There are 16 towers of particle detectors. First the gamma rays have to pass through the anticoincidence detector.
Processing the data
The electron and positron are then passed into the calorimeter to measure their energies, with the combined information then processed by the Data Acquisition System. This works out which signals are real gamma rays and sends the data to scientists to work with.
Above: The blue-coloured plane of the Milky Way shines brightly in gamma rays, but higher energy gamma rays are emitted within the Fermi Bubbles
Passing through the tracker
The rays interact with a tungsten sheet to convert the ray into an electron and positron, the paths of which are measured using silicon strips within a tracker subsystem so that their arrival direction can be determined.
Powering the instruments Solar panels measuring 15 metres (49 feet) from tip to tip are on either side of the instruments. There are also cooling radiators for the Large Area Telescope.