During a chance encounter with what appears to be an unusually strong blast of solar wind at Saturn, NASA's Cassini spacecraft
detected particles being accelerated to ultra-high energies. This is
similar to the acceleration that takes place around distant supernovas.
"Cassini has essentially given us the capability of studying the nature
of a supernova shock in situ in our own solar system, bridging the gap
to distant high-energy astrophysical phenomena that are usually only
studied remotely," said Adam Masters of the Institute of Space and Astronautical Science, Sagamihara, Japan.
Scientists are particularly interested in "quasi-parallel" shocks, where
the magnetic field and the "forward"-facing direction of the shock are
almost aligned, as may be found in supernova remnants. The new study,
led by Masters describes the first detection of significant acceleration
of electrons in a quasi-parallel shock at Saturn, coinciding with what
may be the strongest shock ever encountered at the ringed planet.
Since we can't travel out to the far-off stellar explosions right
now, the shockwave that forms from the flow of solar wind around
Saturn's magnetic field provides a rare laboratory for scientists with
the Cassini mission -- a partnership involving NASA, the European Space Agency and the Italian Space Agency -- to observe this phenomenon up-close. The findings, published this week in the journal Nature Physics, confirm that certain kinds of shocks can become considerably more effective electron accelerators than previously thought.
Shock waves
are commonplace in the universe, for example in the aftermath of a
stellar explosion as debris accelerate outward in a supernova remnant,
or when the flow of particles from the sun - the solar wind - impinges
on the magnetic field of a planet to form a bow shock.
Under certain magnetic field orientations and depending on the
strength of the shock, particles can be accelerated to close to the
speed of light at these boundaries. These may be the dominant source of
cosmic rays, high-energy particles that pervade our galaxy.
Image credit: Coutersy NASA/JPL
Source: The Daily Galaxy via NASA
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