At the end of their lives stars like our sun eject expanding gas shells known as planetary nebulae. Despite being spewed out by spherical stars, some 80 percent of these impressive displays are not spherical themselves, instead they exhibit complex morphologies. Astronomers have now, for the first time, detected magnetic fields in the central stars of four planetary nebulae, suggesting a cause of the irregular structures.

Stefan Jordan of the Astronomisches Rechen-Institut in Heidelberg, Germany, and his colleagues used a tool from the Very Large Telescope at the Paranal Observatory in Atacama, Chile, to measure the polarization of light emitted by stars at the center of planetary nebulae. Because atoms change their energy in response to a magnetic field in a predictable way--a process known as the Zeeman effect--it is possible to calculate the strength of a magnetic field from such polarization measurements. The team analyzed magnetic field data for each of the central stars in the four nonspherical nebulae they studied, and found that their fields reach approximately 1,000 times the strength of the sun's magnetic field.

The team next hopes to search spherical planetary nebulae for any signs of magnetic fields, to test their theory that these forces are responsible for intricately shaped nebulae. The findings will appear in an upcoming issue of the journal Astronomy and Astrophysics.