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Astronomers Report Unprecedented Double Helix Nebula Near Center of the

Subject: Astronomers Report Unprecedented Double Helix Nebula Near Center of the Milky Way Forwarded
From: Andrew Yee
Date: Wed, 15 Mar 2006 18:57:45 -0500
Newsgroups: sci.astro
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FOR IMMEDIATE RELEASE: Wednesday, March 15, 2006

Astronomers Report Unprecedented Double Helix Nebula Near Center of the Milky Way
Astronomers report an unprecedented elongated double helix nebula near
the center of our Milky Way galaxy, using observations from NASA's
Spitzer Space Telescope. The part of the nebula the astronomers observed
stretches 80 light years in length. The research is published March 16
in the journal Nature.
"We see two intertwining strands wrapped around each other as in a DNA
molecule," said Mark Morris, a UCLA professor of physics and astronomy,
and lead author. "Nobody has ever seen anything like that before in the
cosmic realm. Most nebulae are either spiral galaxies full of stars or
formless amorphous conglomerations of dust and gas -- space weather.
What we see indicates a high degree of order."
The double helix nebula is approximately 300 light years from the
enormous black hole at the center of the Milky Way. (The Earth is more
than 25,000 light years from the black hole at the galactic center.)
The Spitzer Space Telescope, an infrared telescope, is imaging the sky
at unprecedented sensitivity and resolution; Spitzer's sensitivity and
spatial resolution were required to see the double helix nebula clearly.
"We know the galactic center has a strong magnetic field that is highly
ordered and that the magnetic field lines are oriented perpendicular to
the plane of the galaxy," Morris said. "If you take these magnetic field
lines and twist them at their base, that sends what is called a
torsional wave up the magnetic field lines.
"You can regard these magnetic field lines as akin to a taut rubber
band," Morris added. "If you twist one end, the twist will travel up the
rubber band."
Offering another analogy, he said the wave is like what you see if you
take a long loose rope attached at its far end, throw a loop, and watch
the loop travel down the rope.
"That's what is being sent down the magnetic field lines of our galaxy,"
Morris said. "We see this twisting torsional wave propagating out. We
don't see it move because it takes 100,000 years to move from where we
think it was launched to where we now see it, but it's moving fast --
about 1,000 kilometers per second -- because the magnetic field is so
strong at the galactic center -- about 1,000 times stronger than where
we are in the galaxy's suburbs."
A strong, large-scale magnetic field can affect the galactic orbits of
molecular clouds by exerting a drag on them. It can inhibit star
formation, and can guide a wind of cosmic rays away from the central
region; understanding this strong magnetic field is important for
understanding quasars and violent phenomena in a galactic nucleus.
Morris will continue to probe the magnetic field at the galactic center
in future research.
This magnetic field is strong enough to cause activity that does not
occur elsewhere in the galaxy; the magnetic energy near the galactic
center is capable of altering the activity of our galactic nucleus and
by analogy the nuclei of many galaxies, including quasars, which are
among the most luminous objects in the universe. All galaxies that have
a well-concentrated galactic center may also have a strong magnetic
field at their center, Morris said, but so far, ours is the only galaxy
where the view is good enough to study it.
Morris has argued for many years that the magnetic field at the galactic
center is extremely strong; the research published in Nature strongly
supports that view.
The magnetic field at the galactic center, though 1,000 times weaker
than the magnetic field on the sun, occupies such a large volume that it
has vastly more energy than the magnetic field on the sun. It has the
energy equivalent of 1,000 supernovae.
What launches the wave, twisting the magnetic field lines near the
center of the Milky Way? Morris thinks the answer is not the monstrous
black hole at the galactic center, at least not directly.
Orbiting the black hole like the rings of Saturn, several light years
away, is a massive disk of gas called the circumnuclear disk; Morris
hypothesizes that the magnetic field lines are anchored in this disk.
The disk orbits the black hole approximately once every 10,000 years.
"Once every 10,000 years is exactly what we need to explain the twisting
of the magnetic field lines that we see in the double helix nebula,"
Morris said.
Co-authors on the Nature paper are Keven Uchida, a former UCLA graduate
student and former member of Cornell University's Center for
Radiophysics and Space Research; and Tuan Do, a UCLA astronomy graduate
student. Morris and his UCLA colleagues study the galactic center at all
NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the
Spitzer Space Telescope mission for the agency's Science Mission
Directorate. Science operations are conducted at the Spitzer Science
Center at the California Institute of Technology. JPL is a division of
Caltech. NASA funded the research.
The double helix nebula. (The image uses false colors because the eye is not sensitive to infrared light.) The spots are infrared-luminous stars, mostly red giants and red supergiants. Many other stars are present in this region, but are too dim to appear even in this sensitive infrared image.
Credit: NASA/JPL-Caltech/UCLA

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