
Credit: X-ray: NASA/CXC/SAO/M.Karovska et al;
Optical: NASA/STScI;
Radio: NRAO/VLA]; Wide field [Optical (DSS)
CH Cygni in a Pinch
Jul 12, 2010
Recent
images of the star CH Cygni
(composite image above) reveal the
electrical circuitry that drives it.
Radiation in radio (blue), optical
(green), and x-ray (red) highlight
the several inner components (inset)
of the plasma discharge.
The outer red circle (large optical
image) is composed of radial
filaments. This is a region of
increased density where the plasma
has jumped into glow mode. It shows
a cross section of the interstellar
Birkeland cable as it pinches down
to form the star. Its circularity
indicates that we are viewing the
star down the axis of the cable: The
radial filaments appear
foreshortened in consequence.
The string of green “sausages” in
the “jet” near the center (inset)
shows the narrowest region of the
pinch as the current flows into the
star. The increase in current
density has again pushed the plasma
into glow mode. Instabilities,
called “sausage” instabilities, have
caused secondary pinches to break
the jet into cells. The curled shape
is the result of viewing the current
down the axis as it spirals around
that axis.
The star at the center is a
binary. Many stars in such “active”
systems (where a surge in the
interstellar current has caused the
outlying components to “light up”)
are multiple. Often they are
composed, as here, of a red giant
and a (so-called) white dwarf. The
details of their operation are
explained toward the end of articles
here and
here.
Mel Acheson
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