Why the upcoming eclipse is still vital in the age of solar probes

Western Europe’s first total solar eclipse since 1999 will happen on 12 August and see eclipse chasers travel to eastern Greenland, western Iceland and northern Spain for totality, when the moon covers the sun’s disc and the usually hidden solar corona bursts into view. Solar and atmospheric scientists will be among them – and above them.

It is tempting to think total solar eclipses have been made obsolete for scientists by spacecraft. NASA’s Parker Solar Probe has flown through the sun’s corona, while the European Space Agency’s Solar Orbiter and NASA’s Solar and Heliospheric Observatory study the sun from space. ESA’s Proba-3 mission can even create artificial eclipses in orbit. So why do scientists still need to chase the moon’s shadow across Earth?

The answer is simple: total eclipses offer cheap and accessible opportunities to study both the sun and Earth. “Research groups that have novel ideas can go to an eclipse and take observations without having to bid for tens of millions of pounds’ worth of grants from NASA or the European Space Agency – the barrier to entry is much lower,” says Ryan French, a solar physicist at the Laboratory for Atmospheric and Space Physics in Boulder, Colorado.

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One example is the Nationwide Eclipse Ballooning Project, which will send teams from several US universities to Spain and Iceland to study atmospheric responses to the eclipse. Balloons released in Spain will reach an altitude of 27 to 37 kilometres, carrying 360-degree cameras, ozone instruments and radio experiments. Icelandic teams will launch balloons carrying radiosondes, devices that can monitor pressure, temperature, humidity and other atmospheric parameters. The idea is to measure the effects the eclipse has on the planetary boundary layer, the atmosphere’s lowest region where its behaviour is most heavily influenced by warm air rising from the ground.

NASA’s WB-57 high-altitude aircraft can measure polarised coronal light and will fly for the 2026 eclipse. Flying high avoids the problem of cloud cover obscuring the view, while also minimising atmospheric interference. “At high altitude, you can observe infrared light that you can’t observe from the ground,” says French.

During the 2024 total solar eclipse, Citizen CATE – an experiment funded by the US National Science Foundation and NASA – used telescopes spread along the path of totality to create a 1-hour timelapse of the corona. This will be repeated during the 2026 eclipse, ahead of a plan to produce a timelapse of the corona with the larger North African Telescope Eclipse experiment during the longer eclipse that will happen in August 2027. Totality in 2027 will last much longer because the new moon will be closer to Earth, and the path of totality is close to the equator, where Earth effectively bulges out towards the moon.

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“Most of the scientific instruments at an eclipse are not just taking photographs, but collecting measurements of spectra,” says French. Spectroscopy can reveal the speed, temperature and density of plasma in the corona. “When you observe specific spectra, this can give you information on the speed of plasma moving in the sun, and can tell you about the temperature and the density of plasma sloshing around the sun,” he says.

Other eclipse scientists ask a fundamental question: what is the radius of the sun? Because the sun has no solid surface, its visible edge is difficult to define. Yet tiny differences can shift the predicted edge of the path of totality. The Besselian Elements Team, a group of researchers scattered across the world, records flash spectra at the path’s edge to refine eclipse maps and calculate the sun’s actual radius.

The eclipse may also offer a rare chance to test whether aurora can be detected during totality. NASA scientist Liz MacDonald, founder of citizen science project Aurorasaurus, will use all-sky cameras to search for faint auroral glow. It is a long shot, but Iceland lies beneath the auroral oval, a region surrounding the geomagnetic North Pole within which the aurora can regularly be seen. Even a non-detection could help constrain whether eclipse darkness can reveal aurora.

Total solar eclipses are brief, vulnerable to clouds and geographically specific, but they open a rare observing window onto the sun’s inner corona – and let scientists try bold ideas without first building a spacecraft.

Discovery Tours: Eclipses

Explore our tours and cruises designed to help you make the most of experiencing awe-inspiring solar eclipses in handpicked locations around the world.