Recreating artificial solar eclipses in space could help astronomers decipher the inner workings of our Sun much quicker than if they had to wait for the celestial show on Earth.
The plan, part of a UK-led space mission to be unveiled at the Royal Astronomical Society's National Astronomy Meeting 2025 in Durham , would involve the use of a mini-satellite and the Moon's shadow to achieve the closest-ever views of the Sun's atmosphere.
The Moon-Enabled Sun Occultation Mission (MESOM) proposes a novel way to study the inner solar corona – the innermost layer of the Sun's atmosphere, which is usually only visible during fleeting total solar eclipses on Earth.
It is being presented by researchers from the Mullard Space Science Laboratory at University College London (UCL), Aberystwyth University, and the Surrey Space Centre, part of the University of Surrey.
If approved, MESOM could operate for two years and capture the equivalent of 80 Earth-based eclipses – an unprecedented opportunity for solar science which could also help researchers gain important clues about how space weather originates.
MESOM would place a small satellite into a special orbit that allows it to align with the Moon's shadow roughly once every 29.6 days – the length of a synodic (lunar) month.
These alignments would mimic the effects of total eclipses, but viewed in space, up to a maximum of 48 minutes – 10 times longer than typical eclipses seen from Earth. Unlike terrestrial observations, the satellite would capture data without interference from Earth's atmosphere.
Co-investigator Dr Nicola Baresi, from the Surrey Space Centre, said: "MESOM capitalises on the chaotic dynamics of the Sun-Earth-Moon system to reproduce total solar eclipse conditions in space while using the Moon as a natural occulter (something which blocks light from a celestial object)."
MESOM's goal is to explore the corona's innermost region, which holds key insights into space weather, solar storms and coronal heating, yet remains poorly understood, partly because it can only be studied under eclipse conditions.
Thanks to its innovative orbital configuration, MESOM would effectively experience a total solar eclipse every synodic month as it naturally passes through the apex of the Moon's umbral cone, or the darkest part of its shadow (every two of its revolutions).
This would allow it to see closer to the Sun than ever before. For comparison, the European Space Agency's (ESA) existing Proba-3 mission observes the corona out from approximately 1.1 solar radii (765,000 km), while MESOM's would reach below 1.02 solar radii (710,000 km), allowing it to get 56,000 km closer to the Sun.
MESOM would carry a suite of instruments, including a high-resolution coronal imager (a telescope to take high-res pictures) proposed to be led by the US Naval Research Laboratory; a corona mass spectrometer (Aberystwyth University and Mullard Space Science Laboratory UCL) to analyse the composition and properties of coronal plasma; and a spectropolarimeter (Spanish Space Solar Physics Consortium, S3PC, Spain) to study the Sun's magnetic field and solar phenomena, like sunspots and flares.
Dr Baresi said: "When the Sun is near the orbital plane of the Moon, we can experience total eclipses as long as 48 minutes, which would enable unprecedented and prolonged measurements of physical processes from which adverse space weather events, namely solar flares and coronal mass ejections, may originate."
The team submitted MESOM to ESA's F-class mission call in May 2025 and expects a response later this year. If selected, it could be launched between 2026-28.
F-class missions are designed to be smaller, faster, and more cost-effective than ESA's larger "M-class" missions, with a ceiling cost of €205 million (£175 million) and a development timeline of less than eight years from selection to launch.
