Explanation:
What shines in the gamma-ray sky?
The
answer is usually the most exotic and energetic
of astrophysical environments, like
active galaxies powered
by supermassive black holes, or incredibly
dense pulsars, the spinning
remnants of exploded stars.
But on March 7,
a powerful
solar flare, one of a series of
recent solar eruptions,
dominated the gamma-ray sky
at energies up to 1 billion times the energy of visible light
photons.
These two panels illustrate the intensity of that solar flare
in all-sky images recorded by the orbiting
Fermi Gamma-ray Space Telescope.
On March 6, as on most days, the Sun was
almost invisible to
Fermi's imaging detectors.
But during the energetic
X-class
flare, it became nearly 100 times
brighter than even the Vela Pulsar
at gamma-ray energies.
Now faded in
Fermi's view, the Sun will likely shine
again in the gamma-ray sky as the solar activity cycle approaches
its maximum.
