China debuts pioneering solar telescope

The world's first solar magnetic-field telescope operating in the mid-infrared wavelength range has officially become operational after gaining government approval, marking a major breakthrough in solar magnetic field research.

The telescope, known as the Accurate Infrared Magnetic Field Measurements of the Sun, or AIMS, is located in Lenghu township, Qinghai province, at an average altitude of about 4,000 meters. AIMS' development addresses a long-standing bottleneck in the century-old history of solar magnetic field measurements by achieving a leap from indirect to direct measurement, scientists said.

"The sun, being the only star we can observe with high precision, has a magnetic field that acts as the energy switch driving intense solar activities such as flares and coronal mass ejections. Yet, more than half the sun's overall magnetic field manifestations are relatively weak, with strengths of only a few dozen gauss," said Deng Yuanyong, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, who led the telescope's construction.

Gauss is the unit used to measure the strength of a magnetic field.

"China's capabilities in traditional magnetic field measurement approaches have been on par with international standards, achieving a 100-gauss precision, which falls short of meeting the requirements for current solar physics studies, "Deng said.

Scientific evaluations show that the newly developed telescope can carry out precise measurements of solar magnetic fields for the first time, with an accuracy better than the 10-gauss level.

"It is the world's first solar magnetic-field telescope operating in the mid-infrared wavelength range and China's first astronomical instrument to work in this band, "Deng said.

He noted that all the key components of the telescope are domestically produced, enhancing China's capacity for independent innovation in astronomical instrumentation.

By adopting an off-axis optical system, the telescope reduces the impact of high environmental background noise in the mid-infrared wavelength range. Combined with cooling and filtering technologies, this design improves the accuracy of magnetic field measurements.

The telescope also employs an infrared-separating spectrograph that enables spectroscopic imaging of the solar atmosphere with high spectral resolution. In addition, the research team has developed a pioneering polarization modulation technique and built a polarization-aberration-free optical system composed of five reflective mirrors to eliminate instrumental polarization errors.

"The telescope is expected to operate year round, weather permitting, with an anticipated 250 days of observation annually. The data collected will support fundamental research in solar physics and advance studies in space weather forecasting," Deng said, adding that he hopes to promote international collaborations with leading research teams in the field.