By Nicola Baresi, University of Surrey; Huw Morgan, Aberystwyth University; and Lucie Green, University College London
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New mission could create artificial solar eclipses in space
When a solar storm strikes Earth, it can disrupt technology that’s vital for our daily lives. Solar storms occur when magnetic fields and electrically charged particles collide with the Earth’s magnetic field. This type of event falls into the category known as “space weather”.
An international team of researchers (including us, the authors of this article) is working on a spacecraft mission that would enable researchers to study the conditions that create solar storms, leading to improved forecasts of space weather.
The proposed mission, known as Mesom (Moon-Enabled Sun Occultation Mission), aims to create total solar eclipses in space. It would use the moon to view the sun’s atmosphere in more detail than ever before.
Why are artificial solar eclipses necessary?
The need for a better understanding of solar storms is evident from looking at past disruptions. In 1989, for example, the sun sent the Canadian province of Quebec into a nine-hour blackout. The cause was a coronal mass ejection (CME); a huge burst of hot plasma and magnetic fields thrown off from the sun’s atmosphere towards space.
The event is estimated to have cost tens of millions of US and Canadian dollars. That’s both in lost business productivity and the need to replace damaged power equipment.
In May 2024, a succession of similar solar eruptions caused thousands of satellites in low-Earth orbit to abruptly drop in altitude. GPS outages cost US farmers alone an estimated US$500 million.
But these storms were significantly weaker than one in 1859, also the result of a CME, which is known as the Carrington Event. Electrical currents flowing through telegraph wires caused operators to receive electric shocks and even started fires in telegraph offices. Today, a Carrington-like event would have far more dramatic consequences on our technology-dependent world.
Yet, our view of the sun’s outer atmosphere, the solar corona – from which CMEs originate – remains dazzled by the bright light of the sun itself. A new UK-led spacecraft mission aims to change that by creating artificial solar eclipses in space.
Better forecasting
During total solar eclipses, the light coming from the surface of the sun is occulted (covered) by the moon. That leaves behind only a faint glow of light coming from the outer layers of the sun’s atmosphere, the corona.
Observing the physical processes in the corona at different timescales and wavelengths is key to enabling better forecasting of space weather. Plus, it could help solve longstanding mysteries of our star. These include how the sun’s evolving magnetic fields confine and release the hot plasma of its volatile atmosphere.
Unfortunately, total solar eclipses are predictable yet rare events that only last for a few minutes. All total eclipses in the 21st century will last less than seven minutes each, and will occur only once every 18 months on average.
Total solar eclipse measurements from the ground are also subject to weather conditions. Plus, Earth’s atmosphere causes observations to suffer from distortions and loss of detail.
A new take on the coronagraph
For decades, scientists and engineers have observed the corona by artificially covering the sun. They do so using clever optics and instrument design inspired by the pioneering work of Bernard Lyot, a French astronomer who first come up with the idea of a “coronagraph”.
Coronagraphs are telescopes equipped with an occulting disk to block out the overwhelming light coming from the visible surface a star.
In a coronagraph, the faint coronal light can be picked up and translated into digital signals. This is the working principle of the Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) spacecraft, which has returned stunning images of the sun’s corona since its launch in 1995.
However, even ground-based and space-based coronagraphs cannot capture images of the deepest layers of the sun’s atmosphere. That’s due to artifacts – artificial effects such as streaks of light that appear in images – and instrument limitations that significantly degrade the quality of the measurements closer to the sun’s surface.
And while the recently launched Proba-3 coronagraph has improved this, it is still unable to image the solar atmosphere’s deepest layers. Proba-3 is a European Space Agency-led technology demonstration mission that relies on a pair of satellites flying in a close formation (up to 150 meters, or 490 feet, apart during observations) to produce artificial solar eclipses in space.
Celestial occulters
UK Airbus engineers Steve Eckersley and Stephen Kemble have proposed an alternative approach. They advocate the use of celestial bodies as natural occulters (covers).
The idea is to fly a spacecraft mission in a celestial object’s shadow to enable prolonged and high-quality measurements of the corona down to the sun’s chromosphere. That is, the layer of the sun’s atmosphere located just below the corona. This would effectively recreate the same total solar eclipse conditions we experience occasionally on Earth, but without the degradations that our planet’s atmosphere causes.
Our celestial neighbour, the moon, is a near-perfect sphere and does not have a thick atmosphere. That makes it among the best natural occulting disks found in the solar system.
A pool of engineers at the Surrey Space Centre has investigated the possibility of using the moon as a natural occulting disk for studying the solar corona, and came up with the Mesom concept.
Mesom is a mini-satellite mission that capitalises on the chaotic dynamics of the sun-Earth-moon system to collect high-quality measurements of the inner solar corona once a month, for observation windows as long as 48 minutes. That’s much longer than the sporadic total solar eclipses on Earth.
Hopes for the future
Funded by the UK Space Agency, the feasibility study of Mesom has grown into a wider international consortium led by UCL’s Mullard Space Science Laboratory and including the Universities of Surrey and Aberystwyth, plus partners from Spain, the US and Australia.
The project has recently been submitted to the European Space Agency for consideration as a future mission. The current mission design proposes a launch in the 2030s, returning at least 400 minutes of high-resolution, low-altitude coronal observations during its two-year nominal science operations.
To collect the same amount of data on Earth, eclipse hunters would have to wait for more than 80 years. This makes Mesom a once-in-a-lifetime opportunity to unravel some of the secrets of the sun’s atmosphere.
Nicola Baresi, Lecturer in Orbital Mechanics, University of Surrey; Huw Morgan, Reader in Physical Sciences, Aberystwyth University; and Lucie Green, Professor of Physics, University College London
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Bottom line: A team of researchers is working on a spacecraft mission that would use the moon to create artificial solar eclipses, aiding with space weather monitoring.
Read more: First images from Proba-3, the 2-part sun observer