For more information about the total solar eclipse on April 8, including where to watch, start time and events happening around San Antonio, check out our guide.
At 2 million degrees Fahrenheit, the sun’s corona — the outermost layer of its atmosphere — is roughly 200 times hotter than the surface of the star.
Scientists are still not sure why that is — but one Southwest Research Institute solar physicist is hopeful the upcoming total solar eclipse will help shine a light on the phenomenon, even as it casts half of San Antonio into semi-darkness.
Amir Caspi, a principal scientist at SwRI based in Boulder, Colorado, will be leading multiple experiments during the cosmic event to help researchers learn more about the sun’s corona.
In Texas, the solar eclipse will take place April 8 around 1:30 p.m. and viewers on the city’s Northwest Side will get to experience totality, with the moon completely blocking out the sun for about four minutes.
One of Caspi’s experiments, which has taken on the name Citizen CATE, will employ more than 100 volunteer “citizen scientists” across the country in the eclipse’s path of totality — the path over which the moon will temporarily completely block out the sun, leaving only the star’s corona visible.
Thirty-five teams — each of which has been given a special telescope and training — will record the eclipse from start to finish from the ground, giving researchers approximately 60 minutes of footage they’ll be able to study afterward. The size of each team ranges from a few members to a whole classroom, Caspi said. Nine of the 35 teams will be based in Texas, he noted.
“Something like 100 million people are in the path of totality or will be driving to the path of totality … so this will probably be the best-observed eclipse in human history so far,” said Caspi, who traveled to Australia last year for a total eclipse.
Caspi’s project received more than 350 applications to participate, and none of the teams consist of formally trained scientists, he said.
“I’m just really excited about the fact that this eclipse crosses over so much populated and easy-to-access land,” Caspi said.
The other experiment Caspi is leading is part of a private-public partnership between SwRI and NASA that will utilize NASA’s WB-57 high-altitude research aircraft. Special cameras from the aircraft will capture images of the eclipse from an altitude of 50,000 feet above Earth’s surface, hopefully allowing researchers to see new details of the corona.
“My experiment is to fly what’s called a multispectral imager,” he said. “It’s basically a telescope with four cameras that measures seven different bands of light, all the way from visible light to the near-infrared, short-wave infrared, and what we call the mid-wave infrared.”
The imager will be in the nose cone of the plane and will be operated by specially trained pilots. High-speed satellite feed from the aircraft will enable scientists and engineers on the ground to share the images and data live.
The total solar eclipse that took place in 2017 was the first time scientists took high-resolution measurements in mid-wave infrared, Caspi said, adding that it’s very difficult to look at the sun with infrared on a normal day because the Earth’s atmosphere glows in that wavelength, blocking out light from the sun.
The only way to overcome this is to get above the Earth’s atmosphere, which is why the plane will be flying at higher altitudes, he added. The corona also glows in infrared, so scientists are hoping to garner brand new measurements that will help tell them how the sun’s atmosphere is structured and how it works.
The eclipse is important because it will block out ultraviolet light that makes the imaging more difficult, he explained.
“So hopefully, we’ll understand things like how the corona gets as hot as it does, and also, where does the solar wind come from?” Caspi said.
Solar wind is a continual stream of protons and electrons from the corona. On Earth, solar wind is responsible for dazzling aurora light shows around the polar regions, but also for geomagnetic storms that can wreak havoc with satellites and electricity networks and threaten astronauts in space.
Learning more about the corona will help scientists continue to grow their knowledge of space weather, which is critical as space exploration continues, Caspi noted.
