China’s first solar observatory aims to solve the mysteries of solar flares

China will open its first dedicated solar observatory. Astronomers say his trio of instruments will provide insights into how the Sun’s magnetic field creates coronal mass ejections and other flares.

The Advanced Space-based Solar Observatory (ASO-S) is scheduled to lift off from the Jiuquan Satellite Launch Center in north China at 7:43 a.m. local time on Oct. 9. China has already sent satellites into space with individual solar observation instruments, but the 900 million yuan ($126 million) ASO-S is its first observatory with a suite of instruments.

Scientists in China have been waiting for the observatory for a long time. They first planned such a mission in the 1970s, says Weiqun Gan, an astrophysicist at the Purple Mountain Observatory of the Chinese Academy of Sciences in Nanjing and the mission’s chief scientist. “We’ve always wanted to do something like this,” he says.

Astronomers know that the Sun’s magnetic field causes its energetic emissions, but unraveling the relationship between the two is notoriously complex. ASO-S will be important for understanding these relationships because its instruments will look across different wavelengths simultaneously, says Eduard Kontar, an astrophysicist at the University of Glasgow, UK, and a member of the mission’s Science Committee. Studying different aspects of solar activity simultaneously allows researchers to link flares to their underlying causes.

ASO-S joins a series of solar missions already in orbit around the Earth or the Sun. “These are very exciting times for solar physicists in China and around the world,” says Kontar.

Four-year mission

ASO-S – also known by its nickname Kuafu-1, after a giant in Chinese mythology who attempted to capture and tame the Sun – will observe from an orbit 720 kilometers above Earth’s surface, permanently facing the Sun.

The mission will last at least four years, according to Gan, covering the peak of the solar cycle in 2024-25, which averages 11 years. “In these peak years, we see a lot of eruptions,” he says.

The sun produces high-energy bursts of radiation known as solar flares and coronal mass ejections (CMEs), slower streams of particles produced by explosions. The main task of ASO-S will be to study the fundamental physics of these flares and their origin in the energy released by the Sun’s distorting and realigning magnetic field. The process is of “great scientific importance, with far-reaching implications for understanding similar phenomena across the universe,” says Kontar.

Solar flares and CMEs can affect Earth as they reach and interact with the planet’s atmosphere. The resulting “space weather” has the potential to disrupt navigation systems and disrupt power grids. ASO-S can help predict space weather by providing data on the shape of magnetic fields on the Sun’s surface that are most likely to cause flares — knowledge that could allow researchers to predict when and where such flares will occur, Gan says .

The observatory’s three instruments include a magnetograph to study the Sun’s magnetic field and an X-ray imaging machine to study the high-energy radiation released by electrons accelerated in solar flares. ASO-S also carries a coronagraph that will look at the Sun in the ultraviolet and visible spectrum to study the plasma produced by flares and CMEs from the Sun’s surface to the Sun’s outer atmosphere or “corona”.

Unique to ASO-S will be its ability to study an important region known as the middle corona — where solar storms are brewing — that has never before been seen in its entirety in the ultraviolet spectrum, says Sarah Gibson, a solar physicist at US National Center for Atmospheric Research in Boulder, Colorado. This will provide new clues about the origins of CMEs, she says.

data transmission

After the probe’s initial commissioning phase of four to six months, the ASO-S data will be available to everyone, and Chinese solar physicists are keen to collaborate, says Jean-Claude Vial, an astrophysicist at Paris-Saclay University.

Data from ASO-S could complement those from other solar observatories. The European Space Agency’s Solar Orbiter, launched in 2020 and flying close enough to the Sun to test its atmosphere, carries a coronagraph similar to that on ASO-S. From their different vantage points, the two instruments will provide complementary observations, Gibson says. NASA’s Parker Solar Probe, launched in 2018, is also flying close to the Sun to study its atmosphere.

X-ray data from ASO-S could also be combined with data from ESA’s Solar Orbiter to provide a stereoscopic view of solar flares, says Kontar. This could lead to the first reliable measurements of “directivity” – how intensely solar flares tend to go in a certain direction – which could provide clues as to how flares accelerate electrons, an important question in solar physics.

ASO-S 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 to be built from the ground up, so the pressure is on, Gan says. “If our ASO-S mission can do a good job, it might be possible to expand these programs and support more missions,” he says.