Explanation:
Exploring the cosmos at extreme energies, the
Fermi Gamma-ray Space Telescope
orbits planet Earth every 95 minutes.
By design,
it rocks to the north and then to the
south on alternate orbits in order to
survey the sky
with its Large Area Telescope (LAT).
The spacecraft also rolls so that
solar panels are kept pointed at the Sun for power,
and the axis of its
orbit precesses
like a top, making a complete rotation once every 54 days.
As a result of these multiple cycles
the paths of gamma-ray sources trace out
complex patterns from the spacecraft's perspective,
like this mesmerising plot of the path of the Vela Pulsar.
Centered on the LAT instrument's field of view, the plot spans 180
degrees and follows Vela's position
from August 2008 through August 2010.
The concentration near the center
shows that Vela was in the sensitive region
of the LAT field during much of that period.
Born in the death explosion
of a massive star within our
Milky Way galaxy,
the Vela Pulsar
is a neutron star spinning 11 times a second, seen
as the brightest persistent source in the gamma-ray sky.
