Scientists prepare to study solar eclipses with high-altitude aircraft and probes orbiting the sun

By | March 31, 2024

For the millions of people in North America who will be treated to a total solar eclipse on April 8, it will be a spectacular show: a chance to watch the moon completely obscure the face of the sun.

But for scientists it’s a rare opportunity to study the Earth, moon and sun “in completely different ways than we normally do,” said Pam Melroy, NASA’s deputy administrator.

One of the agency’s top priorities will be to observe the Sun’s outer atmosphere, or corona, which is normally not visible because the star is too bright. During a total solar eclipse, the corona comes into view as faint streaks around a glowing halo when the moon blocks light from the sun’s surface.

“There are things happening with the corona that we don’t fully understand, and the eclipse gives us a unique opportunity to collect data that could provide insight into the future of our star,” Melroy said in a news briefing last week.

Scientists are interested in the corona because it plays a key role in transferring heat and energy to the solar wind, the constant stream of charged particles released from the Sun’s outer atmosphere. The solar wind ebbs and flows, occasionally shooting powerful solar flares into space. These can hit the Earth with electromagnetic radiation, which can cause radio interference and disable electricity grids.

Amir Caspi, a solar astrophysicist at the Southwest Research Institute in Boulder, Colorado, has installed an instrument in the nose of a WB-57 aircraft that will study the sun’s atmosphere as the plane chases the eclipse.

It’s a golden opportunity, he said, because even the special telescopes that can block a star’s light, known as coronagraphs, 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 the right size in the sky to block the sun’s disk, but not too much more.”

Caspi will focus on understanding the origins of the solar wind. He also hopes to gather 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 to cross the continental US.

“We didn’t know what we were going to get,” he says. “It was nerve-wracking for a long time, and then we got some great data. I could see it coming via 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 Earth’s atmosphere won’t interfere with observations that much.

Many researchers plan to collect data about the Sun’s atmosphere from other vantage points, including from space, during the eclipse.

Several spacecraft, including NASA’s Parker Solar Probe, will set their eyes on the sun during the celestial event. The probe was launched in 2018, so it was not available to study the 2017 solar eclipse.

In 2021, the Parker probe became the first spacecraft to fly through the corona, and since then it has flown more than a dozen close approaches to ‘hit’ 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 the charged particles flow past, said Nour Raouafi, the Parker. Solar Probe project scientist and astrophysicist at the Johns Hopkins Applied Physics Laboratory.

In addition, a European Space Agency spacecraft known as Solar Orbiter will orbit almost directly above the Parker Solar Probe at the time of the eclipse. Together, the observatories will work together to capture details of the Sun’s atmosphere and solar wind.

“It’s one of the rare occasions when these two spacecraft come so close to each other,” Raouafi said. “So we’ll have a lot of synergies between them, between all the observations we’ll make during the eclipse from Earth, which is something totally, totally unprecedented.”

The sun is rising toward a peak in its roughly 11-year activity cycle, expected in 2025. That means the Parker Solar Probe will have a front row seat when eruptions come from the sun.

There are no guarantees that such outbursts will occur during the eclipse, but Raouafi said solar wind measurements from space will still be crucial for understanding the effects of the Sun’s activity on Earth.

“These are the driving forces behind space weather, and the probe is probably the best instrument we have, the best spacecraft mission we have, to help us understand that,” he said. “And the way to do that? Let’s hope the sun will give us the biggest show it can produce.”

Even for non-scientists, the darkness that will temporarily grip the midday sky along the so-called path of totality will be an extraordinary experience.

“I remember the first time I discovered that it’s quite rare – that it just happens to be that our moon is the right size and distance to cause this effect here on Earth,” Melroy said. “It really is a wonder of our universe.”

This article was originally published on NBCNews.com

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