International telescopes capture radiant new magnetic fields spanning entire spiral galaxy

Churning in the inky void of deep space some 67 million light-years from our planet in the constellation Ursa Major is the swirling spiral galaxy officially known as NGC 4217. 

This fertile stellar nursery is similar to our own neighborhood Milky Way, and now astronomers have captured a remarkable new edge-on photo in visible light from the Sloan Digital Sky Survey and Kitt Peak National Observatory. 

Added to the striking imagery are green magnetic field lines that emanate from its borders, unveiled by the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) radio telescope. The incredible galaxy-spanning distances that these blurred magnetic ripples shoot out from NGC 4217 are simply jaw-dropping. This distant galaxy reveals a large-scale, X-shaped, magnetic field structure that covers the majority of its spiraling arms.

Credit: ESA/Hubble & NASA, Acknowledgement: R. Schoofs - NGC 4217

Extending out as much as 22,500 light-years beyond the galaxy’s central core, these shimmering magnetic field lines play a vital role in star formation within active regions of interstellar dust and gas, but the exact mechanics and purposes are still being worked out by international scientists.

Led by Yelena Stein of the Centre de Données astronomiques de Strasbourg, the team's study was published last month in the online journal Astronomy & Astrophysics. 

How these magnetic fields are generated and sustained can be partially explained by a popular notion known as the dynamo theory. This idea postulates that powerful magnetic fields are energized by the dynamic motion of plasma existing within the galaxy’s brilliant spinning disk. Conflicting theories on precisely what delivers these far-reaching vertical bands are less defined, but researchers believe that more comprehensive observations and additional analysis will answer some of the more puzzling questions.

Credit: Y. Stein (CDS), NRAO, SDSS, KPNO 0.9m, J. English (U. Manitoba), R.-J. Dettmar and A. Miskolczi (Ruhr U.), R.J. Rand (U.N.M.), and J. Irwin (Queen’s U.)

“This image clearly shows that when we think of galaxies like the Milky Way, we should not forget that they have galaxy-wide magnetic fields,” explained Stein.

This hypnotic image was created as a composite by Stein, with the help of Jayanne English (University of Manitoba). VLA radio data comes courtesy of Stein and Ralf-Juergen Dettmar (Ruhr University Bochum). Optical data arrived from the Sloan Digital Sky Survey. Ionized hydrogen data (red) herald from the 0.9m telescope of the Kitt Peak National Observatory. The software code for tracing the magnetic field lines was adapted by Stein from Linear Integral Convolution code provided by Arpad Miskolczi of Ruhr University Bochum.