GLAST becomes Fermi ....
NASA's recently launched GLAST gamma-ray observatory has taken its first images, and has been renamed.
It is now the Fermi Gamma-ray Space Telescope, named in honour of
the Nobel-laureate Enrico Fermi. It was Fermi who described how charged
particles in space could be accelerated to high speeds.
The telescope was launched from Cape Canaveral in Florida on 11
June, and is expected to operate for around 10 years, where it will
detect gamma-rays from supermassive black holes and gamma-ray bursts.
Fermi also devised a theory to explain how shock waves and
magnetic fields can accelerate charged particles. The accelerated
particles, called cosmic rays, produce gamma rays when they strike
clouds of gas in space.
At a press conference on Tuesday, scientists released the
telescope's first map of the sky at gamma-ray wavelengths. The map
(below) is built up from 95 hours of observations and was made with an
instrument called the Large Area Telescope, which scans the entire sky
once every 3 hours.
A previous instrument called the Energetic Gamma Ray Experiment
Telescope (EGRET), which flew on NASA's Compton Gamma-ray Observatory,
took more than a year to build a similar map.
Bright spots in the map include the Crab Nebula (M1) which
contains a pulsar, and several quasars. The map’s main feature is a
long ribbon of gamma rays emitted by the disc of our Milky Way galaxy.
Fermi's other instrument, the GLAST Burst Monitor (GBM), is
already detecting gamma-ray bursts on a daily basis. These bursts,
which have been detected in large numbers by NASA's Swift telescope,
are fleeting explosions thought to be caused when massive stars die or
when neutron stars merge.
Fermi's two instruments will allow the telescope to observe the
bursts at a wide – and largely unexplored – range of the energy
spectrum of gamma rays, from 8000 to 30 million electron Volts.
Fermi also boasts a wide field of view, which should enable
astronomers to catch gamma ray bursts when they start and follow them
as they peak and dim, seconds to minutes later.
