Explanation:
Why does the Crab Nebula flare?
No one is sure.
The unusual behavior,
discovered
over the past few years, seems only to
occur in
very high energy light --
gamma rays.
As recently as one month ago, gamma-ray observations of the
Crab Nebula by the
Fermi Gamma Ray Space Telescope showed an
unexpected increase in gamma-ray brightness, becoming about five times the nebula's usual gamma-ray brightness, and
fading again in only a few days.
Now usually the faster the variability, the smaller the region involved.
This might indicate that the powerful pulsar at the
center of the Crab,
a compact neutron star rotating 30 times a second, is somehow involved.
Specifically,
speculation is centered on the changing
magnetic field
that surely surrounds the powerful
pulsar.
Rapid changes in this field might lead to waves of rapidly accelerated electrons which emit
the flares,
possibly in
ways similar to our
Sun.
The above image shows how the Crab Nebula normally
appears in gamma rays, as compared to the
Geminga pulsar, and how it then appeared during the recent brightening.
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