China's FAST telescope detects coherent interstellar magnetic field

Aerial photo taken on Dec. 19, 2021 shows a panoramic view of China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST) under maintenance in southwest China's Guizhou Province. (Xinhua/Ou Dongqu)

Using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), also dubbed as the "China Sky Eye," scientists have obtained accurate magnetic field strength in molecular cloud, a region of the interstellar medium that seems ready to form stars.

Employing the technique of HI Narrow Self Absorption (HINSA), they achieved a clear detection of the Zeeman effect -- the splitting of a spectral line into several components of frequency in the presence of a magnetic field. It is the only direct probe of interstellar magnetic field strength.

The result suggested that such clouds achieve supercritical state, a critical point when they collapse into stars, happened earlier than previously thought based on the standard model.

The study was published in Nature on Jan 5.

Aerial photo taken on Dec. 19, 2021 shows China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST) under maintenance in southwest China's Guizhou Province. (Xinhua/Ou Dongqu)

Photo taken on Dec. 19, 2021 shows China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST) under maintenance in southwest China's Guizhou Province. (Xinhua/Ou Dongqu)

Aerial photo taken on Dec. 19, 2021 shows China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST) under maintenance in southwest China's Guizhou Province. (Xinhua/Ou Dongqu)

Staff members conduct maintenance work at China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in southwest China's Guizhou Province, Dec. 17, 2021. (Xinhua/Ou Dongqu)

A staff member conducts maintenance work at China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in southwest China's Guizhou Province, Dec. 17, 2021. (Xinhua/Ou Dongqu)