picture of the day
Credit: NASA, ESA and The Hubble Heritage Team (STScI/AURA).
Jun 13, 2007
Boomerang Nebula Comes Back—to Plasma
A cold nebula provides
evidence of electrical activity at temperatures near
The Boomerang Nebula exhibits the
bipolar symmetry that
has become typical of planetary nebulae: two cones or,
often, bubbles of material radiate away from the central
star (which is often a double star). In most nebulae, the
plasma is sufficiently dense and excited to emit light. But
the Boomerang Nebula is cold: Radio measurements indicate
the inner part is only one degree above absolute zero. We
are able to see the nebula because dust particles reflect
light from the central star.
this image from the Hubble Space Telescope, the false colors
indicate polarization angles of the reflected light. By
analyzing how the light from different parts of the nebula
are polarized, astronomers can determine such properties as
the size and alignment of the dust particles. They hope that
this information will shed light on the most pressing
question: How can a spherical star, powered internally by
nuclear fusion, eject material only along its axis? If only
gravity and hot gas provide the forces for ejection, the
ejection should be spherical.
Some theorists speculate that perhaps a disk of material
around the star’s equator—seen in a number of nebulae—blocks
ejected material from that direction. But what generated the
disk, and how does it remain intact in the face of such
ejection? Other theorists speculate that magnetic fields
constrain the outflow. But what generates and powers the
Electric Universe takes note of the
of the cones and of the way the filaments spiral into and
away from the central star. It also takes note of the string
of cells or bubbles along the axis of the cones. Spiraling
filaments around cells of plasma are the forms taken by
electric currents in space. The filaments are called
Birkeland currents, named after
who first proposed their existence in the late 1800s.
from a star, these currents form tubes of plasma that
transmit electrical power around a galaxy. At intervals, the
electromagnetic forces that they generate cause them to
pinch down to a very much smaller size. Plasma accumulates
in the center of the pinch. The increased current density
causes it to shine, producing and powering a star. Usually,
the plasma surrounding the star is also hot, producing the
glow of an emission nebula. But with the proper conditions
of opacity and density, the surrounding plasma can be cold,
as in the Boomerang Nebula, revealing its presence only by
reflected light and radio emission.
Plasma theorists would not be surprised if closer
observations discover a disk of material around the star’s
equator. In lab experiments and in computer simulations of
the pinch effect, a “ring current”—a doughnut-shaped flow of
plasma and electricity—circles the central accumulation of
plasma. Power flows into the ring current, which stores it
until a threshold is reached. Then the ring discharges to
the central body.
the ring doesn’t block an equatorial outflow: The magnetic
field generated by the pinched-down Birkeland current that
powers the star confines the flow of plasma from the star
into the axial jets.
gravitational theorists have guessed the forms, but they
still have no explanation why the forms are there.