It will be a spectacular spectacle for millions of people in North America who will encounter a total solar eclipse on April 8; There will be a chance to see the moon completely obscuring the sun’s face.
But for scientists, this is a rare opportunity to study the Earth, moon and sun “in completely different ways than we usually do,” said NASA deputy administrator Pam Melroy.
One of the agency’s main priorities will be to observe the sun’s outer atmosphere, or corona, which normally cannot be seen because the star is so bright. During a total solar eclipse, when the moon blocks light from the sun’s surface, the corona appears as faint tufts around a bright halo.
“There are things going on with the corona that we don’t fully understand, and the eclipse gives us a unique opportunity to collect data that can provide insight into the future of our star,” Melroy said at a news briefing last week.
Scientists are interested in the corona because it plays an important role in transferring heat and energy to the solar wind, a constant flow of charged particles released from the sun’s outer atmosphere. The solar wind ebbs and flows, occasionally shooting high-powered solar flares into space. These can hit the Earth with electromagnetic radiation, causing radio outages and disabling power grids.
Amir Caspi, a solar astrophysicist at the Southwest Research Institute in Boulder, Colorado, installed an instrument in the nose of aircraft WB-57 that will study the sun’s atmosphere as the aircraft tracks the eclipse.
This is a golden opportunity, he said, because even special telescopes known as coronagraphs that can block a star’s light have limitations.
“A total solar eclipse is like nature’s perfect coronagraph,” he said. “The moon comes between us and the sun, and is just big enough in the sky to cover the sun’s disk, but not much more.”
Caspi will focus on understanding the origin of the solar wind. He also hopes to glean clues about a long-standing mystery: why the corona is millions of degrees hotter than the surface of the sun.
He pioneered this method of imaging the sun’s corona in 2017, during the last total solar eclipse that crossed the continental United States.
“We didn’t know what to buy,” he said. “It was exciting for a long time, then we got incredible data. I could see it coming from the live satellite feed.”
The WB-57 aircraft can fly at an altitude of 60,000 feet, well above any clouds and high enough that the Earth’s atmosphere does not interfere much with observations.
Many researchers plan to collect data on the sun’s atmosphere during the eclipse from other vantage points, including space.
Many spacecraft, including NASA’s Parker Solar Probe, will have their eyes trained on the sun throughout the celestial event. Because the probe was launched in 2018, it was not possible to study the 2017 solar eclipse.
In 2021, the Parker probe became the first spacecraft to fly across the corona, and has since made more than a dozen close-in missions to “touch” the sun. Due to the timing of its orbit, the probe will not have a close encounter on April 8. But it will be close enough to the sun to measure and image the solar wind as charged particles pass by, according to Parker Nour Raouafi. Solar Probe project scientist and astrophysicist at the Johns Hopkins Applied Physics Laboratory.
Additionally, a spacecraft from the European Space Agency known as Solar Orbiter will circle almost directly above Parker Solar Probe during the eclipse. Together, the observatories will team up to capture details of the sun’s atmosphere and solar wind.
“It is one of the rare cases that these two spacecraft come so close to each other,” Raouafi said. “So between all the observations we’ll make from Earth during the eclipse, there will be a lot of synergy between them, which is completely unprecedented.”
The Sun is rising toward its peak in its roughly 11-year activity cycle, which is expected to occur in 2025. This means that if there is any solar flare, the Parker Solar Probe will be in the front row.
There’s no guarantee that such outbursts will occur during the eclipse, but Raouafi said solar wind measurements from space will still be crucial to understanding the effects of solar activity on Earth.
“These are the drivers of space weather, and the probe is probably the best instrument we have, the best spacecraft mission to help us understand that,” he said. “So the way to do this? Let’s hope the sun gives us the greatest show it can produce.”
The darkness that will temporarily take over the afternoon sky along the path of totality will be an extraordinary experience even for non-scientists.
“I remember when I first learned that this was something so rare – it just happened that our moon was the right size and distance to have this effect here on Earth,” Melroy said. “This is truly a miracle of our universe.”
This article first appeared on NBCNews.com.