Explanation:
The pixelated planet above is actually our own planet
Earth
seen in gamma rays - the most energetic form of light.
In fact, the
gamma rays used to construct
this view pack over
35 million electron volts
(MeV) compared to a mere two electron
volts (eV) for a typical visible light photon.
The Earth's
gamma-ray glow
is indeed very faint, and this
image was constructed by combining data from
seven years of exposure during
the life of the
Compton Gamma Ray Observatory,
operating in Earth orbit from 1991 to 2000.
Brightest near the edge and faint near the center,
the picture indicates that the gamma rays are coming from
high in Earth's atmosphere.
The gamma rays are produced as the atmosphere interacts with
high energy cosmic rays from space,
blocking the harmful
radiation from reaching the surface.
Astronomers need
to
understand Earth's gamma-ray glow well
as it can interfere with observations of
cosmic
gamma-ray sources
like pulsars, supernova remnants,
and distant active galaxies powered
by supermassive black holes.
