"These particular loops have never been seen [before]. They've only been known about theoretically," he said.
"Nobody has convincingly identified any galactic loops [until now] … and that makes them quite interesting."
Fukui and his colleagues suggest that the loops they observed are the product of a particular kind of disturbance known as the Parker instability.
This type of disturbance, which is known to occur on the sun, would be responsible for the magnetic buoyancy that supports the gas loops.
Morris, the UCLA astrophysicist, says that any number of cosmic events can initiate the disturbance.
In theory, an event such as a star's explosion can start a ripple in the magnetic field lines that run parallel to the galactic plane.
As the once-straight lines begin to undulate like waves, gas will slip from the peaks and begin to pool in the troughs.
The depressions get even deeper as higher concentrations of gas are pulled downward by the gravitational force of stars in the central plane of the galaxy.
Likewise, as gas flows into the troughs, weight is lifted from the magnetic field's peaks, which can then expand like a balloon.
The Parker instability would explain the loops of gas extending above the galaxy's center (the peaks) and the dense clouds of gas that pool where the loops meet the galactic plane (the troughs).
Loops and Stars
But, Morris says, the Japanese team's report still leaves open some important questions.
One issue is that researchers had expected such loops to contain lighter gases made from individual atoms, such as hydrogen.
Instead the Japanese researchers report that the observed loops carry heavier gases made of molecules, such as carbon monoxide.
"I don't necessarily claim that it's a problem for [the Parker instability] theory," Morris said. "It just doesn't match our expectations."
Another sticking point, he adds, is that researchers must now confirm that the loops seen by the Japanese team are indeed caused by magnetic fields—a difficult task given that magnetism can't been visually observed.
Ultimately, understanding such loops could be significant, Morris says, because the features may play a key role in star formation in the Milky Way and other galaxies (related image: star formation in the Orion Nebula).
Gravitational forces whirl most of the gas, dust, stars, and other matter in our galaxy into a flat, rotating disk centered on a supermassive black hole.
But the two giant loops observed by the Japanese team float above the main surface, or plane, of our Frisbee-shaped galaxy, buoyed—in theory—by magnetic fields.
These loops reconnect to the main plane of our galaxy at regions known as foot-points, areas where molecular gas naturally concentrates.
Such pools of dense molecular gas are what create the right conditions for star formation.
Morris said that "the concentration of gas at the footprints of the loops has been considered for a long time as a plausible mechanism for inducing star formation."
The astrophysicist noted that scientists could easily confirm this theory using NASA's orbiting Spitzer Space Telescope to "see if there's a lot of star formation activity" in these zones.
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