Light from the Sun’s upper atmosphere silhouettes the Moon in this photo of the 21 August 2017 total solar eclipse, which was taken from Earth’s stratosphere. A bright ring of light emitted by the Sun’s uppermost layers surrounds the dark circle of the Moon. Light green wisps and tendrils of the corona extend outward. This image is an integration of multiple observations taken in a narrow green wavelength range.
Scientists chased the eclipse using two of NASA’s WB-57F high-altitude research aircraft to obtain this image and other measurements. The aircraft flew at altitudes higher than 15 kilometers along the path of totality. The team continuously observed the eclipse using two 22-centimeter telescopes mounted aboard the craft that are tuned to see in green (approximately 530 nanometers), in the visible continuum (400–700 nanometers), and at medium-wave infrared (3- to 5-micrometer) wavelengths. Imaging the Sun in green light helped the team focus on the light emitted by the corona itself rather than light produced by lower layers and scattered by the ultrahot, diffuse gas.
Observing the eclipse from the stratosphere has some major advantages, the researchers explained yesterday at the Triennial Earth-Sun Summit in Leesburg, Va., where they presented their initial results. By moving up to the stratosphere, the observers avoided weather and other atmospheric disturbances that would have degraded the quality of the measurements or prohibited them entirely.
What’s more, the team greatly increased the overall eclipse observing time. An eclipse observer on the ground may have had up to 2 minutes and 40 seconds of totality, but the pair of flying telescopes continuously observed the eclipse for more than 7 minutes and 30 seconds as they chased totality across the United States.
The researchers are continuing to process the results from this observing campaign and plan to make available to the public all of their raw and processed data, as well as additional measurements obtained during the partial and total eclipse phases. They also hope to repeat these and other observations with better eclipse-specific instruments that can take sharper and cleaner images during the 2019 and 2020 total solar eclipses over South America.
—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer