China is preparing to launch the world’s first dedicated solar observatory. Astronomers believe the spacecraft’s three instruments will shed light on how the Sun’s magnetic field causes coronal mass ejections and other outbursts.
The Advanced Space-based Solar Observatory (ASO-S) is set to launch from the Jiuquan Satellite Launch Center in northern China on October 9 at 7.43 a.m. local time. China has previously launched satellites with separate sun-gazing sensors into space, but the ASO-S, which costs 900 million yuan (US$126 million), is the country’s first observatory with a suite of tools.
Scientists in China have been waiting for the observatory for a long time. They first proposed such a project in the 1970s, according to Weiqun Gan, an astrophysicist at the Chinese Academy of Sciences’ Purple Mountain Observatory in Nanjing and the expedition’s main scientist. “This is something we’ve always wanted to do,” he says.
Astronomers understand that the Sun’s magnetic field is responsible for its energetic emissions, but understanding the link between the two is notoriously difficult. According to Eduard Kontar, an astrophysicist at the University of Glasgow, UK, and a member of the mission’s science committee, ASO-S will be vital for understanding these linkages because its instruments look across multiple wavelengths at once. Researchers can link eruptions to their underlying causes by studying multiple parts of the Sun’s activity at the same time.
ASO-S is the latest in a long line of solar missions orbiting Earth or the Sun. “This is an exciting time for solar physicists in China and around the world,” Kontar says. ASO-S, also known as Kuafu-1 after a Chinese mythological giant who strove to capture and tame the Sun, will watch from an orbit 720 kilometers above Earth’s surface, always facing the Sun. According to Gan, the mission will last at least four years, encompassing the apex of the solar cycle in 2024-25, which lasts 11 years on average. “We can see a lot of eruptions during these peak years,” he says.
Solar flares are high-energy bursts of radiation produced by the Sun, and coronal mass ejections (CMEs) are slower streams of particles produced by explosions. The primary mission of ASO-S will be to investigate the fundamental physics of these eruptions, as well as their sources in energy released by the Sun’s contorting and realigning magnetic field. According to Kontar, the process is of “huge scientific importance, with broad implications for understanding analogous processes throughout the universe.”
When solar flares and CMEs reach and interact with Earth’s atmosphere, they can have an impact. The resulting “space weather” has the potential to damage navigation systems and electrical infrastructures. According to Gan, ASO-S can aid in space weather forecasting by providing data on the configuration of magnetic fields on the Sun’s surface that are most likely to generate eruptions – knowledge that could allow researchers to predict when and where such eruptions will occur.
A magnetograph to investigate the Sun’s magnetic field and an X-ray imager to study the high-energy radiation emitted by electrons accelerated in solar flares are among the observatory’s three instruments. ASO-S also contains a coronagraph, which will examine the plasma created by flares and CMEs from the solar surface to the Sun’s outer atmosphere, or ‘corona,’ in the ultraviolet and visible ranges.
The capacity to examine an essential region known as the middle corona — where solar storms form — in its totality in the ultraviolet spectrum will be unique to ASO-S, according to Sarah Gibson, a solar physicist at the US National Center for Atmospheric Research in Boulder, Colorado. According to her, this will provide new insights into the origins of CMEs. According to Jean-Claude Vial, an astrophysicist at Paris-Saclay University, after the probe’s initial four-to-six-month commissioning phase, ASO-S data will be free for anybody to access, and Chinese solar physicists are keen to contribute.
ASO-S data could be used to supplement data from other solar observatories. A coronagraph identical to that on ASO-S is carried by the European Space Agency’s Solar Orbiter, which launched in 2020 and travels close enough to the Sun to sample its atmosphere. According to Gibson, the two devices will give complementing observations due to their various perspective positions. The Parker Solar Probe, launched by NASA in 2018, also flies close to the Sun in order to sample its atmosphere.
According to Kontar, X-ray data from ASO-S might be coupled with data from ESA’s Solar Orbiter to provide a stereoscopic perspective of solar flares. This could lead to the first credible measurements of ‘directivity,’ or how intense solar flares tend to be in a specific direction, which could provide insight into how flares accelerate electrons, a major subject in solar physics.
The ASO-S mission is part of the Chinese Academy of Sciences’ Strategic Priority Research Program on Space Science, which has launched missions such as the Quantum Experiments at Space Scale satellite and the HXMT X-ray telescope. ASO-S is the program’s first mission from the ground up, therefore the pressure is on, according to Gan. “If our ASO-S mission is successful, it may be conceivable to expand these programs and assist other missions,” he says.