How galactic spiral arms form reavealed

A new study has provided a deeper insight into how galactic spiral arms are formed and how gas can be funneled inward toward the galaxy's center, which possibly hosts a black hole.

Astronomers making a detailed, multi-telescope study of a nearby galaxy have discovered a magnetic field coiled around the galaxy's main spiral arm.

The scientists studied a galaxy called IC 342, some 10 million light-years from Earth, using the National Science Foundation's Karl G. Jansky Very Large Array (VLA), and the MPIfR's 100-meter Effelsberg radio telescope in Germany. Data from both radio telescopes were merged to reveal the magnetic structures of the galaxy.

The surprising result showed a huge, helically-twisted loop coiled around the galaxy's main spiral arm. Such a feature, never before seen in a galaxy, was strong enough to affect the flow of gas around the spiral arm.

The new observations provided clues to another aspect of the galaxy, a bright central region that may host a black hole and also is prolifically producing new stars. To maintain the high rate of star production requires a steady inflow of gas from the galaxy's outer regions into its center.

The scientists mapped the galaxy's magnetic-field structures by measuring the orientation, or polarization, of the radio waves emitted by the galaxy. The orientation of the radio waves is perpendicular to that of the magnetic field. Observations at several wavelengths made it possible to correct for rotation of the waves' polarization plane caused by their passage through interstellar magnetic fields along the line of sight to Earth.