Development in Detection of Gamma rays
are a form of electromagnetic radiation that have the highest energy. Gamma-rays
have frequencies greater than about 1019 hertz (Hz), and wavelengths of less than 100 picometers. Due
to the high energy, they are only produced by the hottest and most energetic
objects in the universe, such as neutron stars and pulsars, supernova
explosions, and regions around black holes.
were first observed by a French scientist called Paul Villard in the 1900’s
whilst he was studying radioactive decay from Radium. Ernest Rutherford continued
on from Villard’s work and found that unlike alpha and beta, gamma rays could
not be deflected by a magnetic field, as they had no charge. In 1914, gamma
rays were observed to be reflected from crystal surfaces, proving that they
were electromagnetic radiation, and therefore had no mass.
rays get absorbed by the earths atmosphere, gamma ray astronomy could not
develop until it was possible to get the detectors above the atmosphere, using satellites.
In 1961, the Explorer 11 was the first to pick up gamma ray photons coming from
various places from the universe. However, the first significant discovery came
between 1960-1980 by the Orbiting Solar Observatory satellite as well as others
launched by NASA, where these satellites provided greater insight into the
high-energy universe, explosions and high-speed collisions. However, the
resolution of these satellites was very poor and therefore it was very
difficult to pinpoint the source of the gamma rays.
The most recent gamma ray telescope
to launch into space was the Fermi Gamma-Ray Space Telescope, which has
discovered and observed many events in the universe such as First
Gamma-Ray-Only Pulsar, which is a rapidly spinning neutron star, the crushed
core left behind when a massive sun explodes. It also witnessed the greatest gamma
ray burst energy release, which had the power of about 9,000 ordinary
supernovae, whose ejected material moved at a minimum of 99.9999% the speed of
light. Fermi also detected the Milky Way gamma/x-ray bubbles, which extend
25000 light years above and below the centre of the galaxy.
still several unproved theories that scientists are still searching for using
gamma ray telescopes such as Fermi. Scientists have searched for evidence of
dark matter annihilation, to prove the theory of WIMP (Weakly Interacting
Massive Particle). The theory states
that If dark matter particles are their own antiparticle, they would annihilate
when they come into contact with each other, producing various particles,
including highly energetic gamma-rays. As shown by the picture above, there are
many gamma rays being emitted in the universe and therefore it is very
difficult to detect individual ones making this theory quite hard to prove.
into gamma ray technology has definitely changed our view of the universe into
a place where Solar flares, supernovae, neutron stars, black holes, and active
galaxies can be identified and studied in great detail. Gamma-ray astronomy allows
us to explore these unique objects and by exploring the universe at these high
energies, scientists can search for new physics, testing theories and
performing experiments which are not possible in earth-bound laboratories.