Each time the Moon covers the Sun during a total solar eclipse — darkening daytime skies and briefly revealing the Sun’s ethereal outer atmosphere, the corona — it presents new opportunities to better understand our star and its profound influence on Earth. These fleeting moments, where the Sun’s outermost layers become visible to terrestrial observers, are invaluable for advancing heliophysics, the study of the Sun and its interaction with the solar system. The upcoming total solar eclipse on Wednesday, August 12, 2026, which will sweep across Greenland, Iceland, and Spain, is no exception. NASA-funded science teams are meticulously preparing to chase the Moon’s shadow with sophisticated high-altitude jets and an array of scientific balloons, aiming to investigate the Sun’s dynamic processes and the temporary darkening of our skies affects Earth’s intricate atmosphere.
The Unique Scientific Window of a Total Solar Eclipse
Total solar eclipses offer a singular advantage for solar physicists. The Moon acts as a perfect natural coronagraph, blocking the intensely bright solar disk and allowing the faint corona to be observed directly from Earth. This phenomenon is a cosmic rarity, as the Moon’s apparent size in the sky is almost precisely the same as the Sun’s. While specialized space-based instruments, known as coronagraphs, can create artificial eclipses to study the corona, they often struggle to observe the very lowest part of the corona, closest to the solar surface, where much of the Sun’s most energetic activity originates. This region is critical for understanding phenomena such as the solar wind and coronal mass ejections (CMEs).
"From our unique perspective on Earth during a total solar eclipse, scientists can study the Sun’s corona in a way we can’t from anywhere else in the solar system," stated Kelly Korreck, eclipse program manager at NASA Headquarters in Washington. "The Sun impacts our daily life, satellites, and astronauts in space, and we can take advantage of this moment to advance our understanding of that influence." The Sun’s activity directly affects Earth’s technological infrastructure, from communications satellites and GPS systems to power grids, highlighting the urgency and relevance of these investigations. Understanding the intricate physics of the corona is paramount for improving space weather prediction models, which are crucial for protecting our assets in orbit and on the ground.
High-Altitude Pursuit: NASA’s WB-57 and the SCIFLI Mission
A cornerstone of NASA’s observational strategy for the 2026 eclipse involves the deployment of its venerable WB-57 high-altitude research aircraft. This modified bomber, renowned for its ability to operate at altitudes far above commercial air traffic, will carry a sophisticated suite of instruments into the stratosphere. Soaring in the nose cone of NASA’s WB-57 is the Scientifically Calibrated In-Flight Imagery (SCIFLI) Multispectral Airborne Imager, or SAMI, an instrument developed by the SCIFLI team at NASA’s Langley Research Center in Hampton, Virginia.
The SAMI instrument comprises four highly sensitive cameras designed to capture high-resolution images of the corona across several different wavelengths of visible and infrared light. Operating at an impressive rate of at least 20 images per second, these cameras will meticulously record the fine structures, outflows, and rapid changes occurring within the corona during the brief period of totality. The inclusion of infrared capabilities is particularly significant, as many infrared wavelengths are absorbed by the lower atmosphere before reaching ground-based telescopes. Observing in these wavelengths from 50,000 feet (approximately 15,240 meters) allows scientists to access previously underexplored spectral regions of the corona, offering new insights into its composition and dynamics. Prior to these high-altitude campaigns, such infrared observations of the corona have been exceedingly rare.
The primary scientific objectives for the WB-57 mission are ambitious and address some of the longest-standing mysteries in heliophysics:
- Coronal Heating Problem: Scientists aim to gather data that could shed light on why the Sun’s corona is heated to nearly a million degrees Celsius, while the solar surface beneath it is a comparatively cooler 5,500 degrees Celsius. This paradoxical temperature inversion remains one of the most perplexing challenges in astrophysics.
- Formation of Prominences: The high-resolution imagery will help researchers better understand the formation and evolution of prominences – vast loops of solar material, often hundreds of thousands of kilometers long, that are suspended above the Sun’s surface by magnetic fields.
- Solar Wind Origin: The mission will investigate the intricate relationship between the material in the corona and the solar wind, the continuous stream of charged particles that flows out from the Sun, permeating the entire solar system and influencing planetary magnetospheres.
By "chasing" the Moon’s shadow, the WB-57 jet significantly extends the duration of coronal observation. While observers on the ground will experience a maximum totality of approximately two minutes and 18 seconds, the jet, flying along the eclipse path at a speed of 460 miles per hour (about 740 kilometers per hour), will extend its view of the corona to nearly three minutes. This extended observation window provides invaluable additional seconds for capturing dynamic processes that unfold rapidly within the corona. Furthermore, operating at 50,000 feet places the aircraft well above any potential cloud cover, ensuring an unobstructed view of the eclipse, a critical advantage over ground-based observations which are always susceptible to meteorological conditions.
The SAMI instrument has a proven track record, having previously flown on a WB-57 during the total solar eclipse on April 8, 2024, across North America. That mission provided invaluable imagery and preliminary information about the corona. Amir Caspi, the principal investigator for the study from the Southwest Research Institute in Boulder, Colorado, emphasizes that each total solar eclipse offers unique opportunities. "The Sun is always changing," Caspi remarked. "Every eclipse is different. So we could see things we didn’t see before. And we learn from each eclipse how to better observe the next one." Building on the experiences of 2024, Caspi’s team is implementing several enhancements for the 2026 campaign. These include adjusting exposure times to prevent overexposure of bright coronal features observed previously and leveraging new software developed since 2024 to accelerate the processing and analysis of the vast amounts of data collected. This continuous refinement ensures that each successive eclipse mission yields progressively more detailed and accurate scientific returns. The experiment is funded by NASA’s Heliophysics Low Cost Access to Space Program, underscoring NASA’s commitment to innovative and cost-effective research initiatives.
Probing Earth’s Atmosphere: The Nationwide Eclipse Ballooning Project
Beyond the solar corona, the sudden onset of darkness during a total solar eclipse provides a unique natural experiment for studying Earth’s atmosphere. When daytime skies abruptly turn dark, our atmosphere undergoes rapid changes that scientists are still working to fully comprehend. The NASA-supported Nationwide Eclipse Ballooning Project (NEBP), led by Angela Des Jardins at Montana State University, is mobilizing student teams from various U.S. universities to deploy scientific balloons in Iceland and Spain. Their mission is to launch these balloons before, during, and after the eclipse to gain a deeper understanding of these atmospheric perturbations. This initiative not only contributes vital scientific data but also fosters hands-on learning and workforce development for the next generation of scientists and engineers.
In Iceland, two dedicated NEBP teams are preparing an ambitious launch schedule. They plan to deploy a total of 80 balloons, commencing 18 hours before the eclipse and continuing until eight hours afterward. These balloons are equipped to study how the eclipse specifically affects Earth’s "boundary layer," the lowest part of the atmosphere that directly interacts with the ground. The boundary layer’s thickness and characteristics are highly dynamic, influenced by factors such as surface temperature, solar radiation, and moisture content in the air.
Previous balloon flights conducted during solar eclipses in October 2023 and April 2024 yielded intriguing results: the boundary layer was observed to "collapse," or significantly decrease in thickness, in locations experiencing clear skies. However, this phenomenon was not consistently observed in areas with heavy cloud cover. Scientists are eager to determine if the 2026 eclipse will present different results in Iceland. The unique geographical and temporal conditions in Iceland in August, characterized by very long days and short nights, mean that the typical diurnal (day-night) cycle influences on the boundary layer might be less pronounced than in previous eclipse observations. "Will this eclipse be able to collapse the boundary layer?" pondered Matthew Bernards, a chemical engineering professor at the University of Idaho, who leads one of the Iceland teams, highlighting the specific questions his team hopes to answer. The answers could refine our understanding of how atmospheric layers respond to rapid changes in solar forcing.
Meanwhile, in Spain, three other NEBP balloon teams will launch a total of six balloons. These balloons are equipped with 360-degree cameras to capture stunning panoramic images of the eclipse shadow as it sweeps across the landscape from above. In addition to visual documentation, these balloons will carry instruments specifically designed to measure atmospheric ozone levels. Ozone, a crucial component of Earth’s stratosphere that shields life from harmful ultraviolet radiation, requires sunlight for its formation. Similar balloon experiments during the April 2024 eclipse indicated a measurable decrease in ozone concentrations during totality. Scientists are curious to observe any differences in ozone response during the 2026 eclipse, particularly given its occurrence at a later time of day and in a different season, which could influence atmospheric chemistry and dynamics. These investigations into the atmospheric boundary layer and ozone are critical for improving regional weather forecasting models and understanding the finer details of atmospheric responses to sudden environmental changes.
Broader Implications and Future Outlook
The comprehensive data collected from both the high-altitude WB-57 mission and the widespread ballooning project will have far-reaching implications for several fields of science. The insights gained into the coronal heating problem, solar wind acceleration, and CME initiation mechanisms will significantly enhance our ability to predict space weather events. Accurate space weather forecasts are increasingly vital in our technologically dependent world, helping to safeguard satellites, protect astronauts, and prevent disruptions to power grids and communication systems on Earth.
Furthermore, the atmospheric studies conducted by the NEBP teams will contribute to a more nuanced understanding of how Earth’s atmosphere responds to rapid changes in solar radiation. This knowledge can inform and refine climate models, particularly concerning the effects of short-term solar variability and sudden temperature shifts on atmospheric stability and composition. The educational component of the NEBP is also a critical investment, inspiring and training a new generation of scientists, engineers, and educators through direct involvement in cutting-edge research.
While the total solar eclipse on August 12, 2026, will not be visible in the continental United States, some parts of the country will be able to witness a partial solar eclipse. For those planning to observe any part of this celestial event, it is crucial to prioritize safety. Direct viewing of the Sun, even when partially eclipsed, can cause permanent eye damage. Observers must use certified solar eclipse glasses or viewers that comply with international safety standards (ISO 12312-2) or employ indirect viewing methods, such as pinhole projectors. NASA provides extensive resources and guidelines for safe eclipse viewing.
Looking ahead, the scientific community eagerly anticipates future total solar eclipses, each promising to reveal new facets of our dynamic star and its intricate connection to our home planet. The detailed planning and execution of missions like those for the 2026 eclipse underscore humanity’s enduring quest to understand the universe around us, one celestial event at a time. The cumulative knowledge from these efforts steadily builds a more complete picture of the Sun-Earth system, fostering both scientific discovery and practical benefits for society.
by Vanessa Thomas
NASA’s Goddard Space Flight Center, Greenbelt, Md.
