Eclipse Science Along the Path of Totality – GWC Mag

In general, scientists don’t put much credence in cosmic coincidences.

But a total solar eclipse—a phenomenon made possible by the remarkable similarity between the apparent sizes of the Sun and the Moon—is likely to awe even the most data-driven researcher. And on 8 April 2024, millions of people across the United States will be treated to such a spectacle as the Moon’s umbral shadow arcs from Texas to Maine.

Researchers and educators are gearing up for the event with a plethora of scientific investigations, many of which welcome the participation of amateur scientists.

Other solar eclipses have been visible from the United States in the recent past. On 14 October 2023, sky watchers in parts of Oregon, California, Nevada, Utah, Arizona, Colorado, New Mexico, and Texas were treated to an annular solar eclipse; viewers in the rest of the contiguous United States saw a partial solar eclipse.

On 21 August 2017, millions of people converged on a roughly 110-kilometer-wide swath to witness the first total solar eclipse visible from coast to coast in the United States in 99 years.

But the roots of recent eclipse mania in the United States can be traced to 21 August 2017. On that day, millions of people converged on a roughly 110-kilometer-wide swath stretching from Oregon to South Carolina—the so-called path of totality—to witness the first total solar eclipse visible from coast to coast in the United States in 99 years.

Observers enjoyed fewer than 3 minutes of totality, but cities across the country held events to celebrate the Moon’s brief—but perfect—passage. And scientists, professionals, and enthusiasts alike were busy collecting data afforded by the rare glimpse of the Sun’s outer atmosphere, its corona.

Three total solar eclipses have occurred since 2017. However, they were witnessed by relatively few people because totality occurred largely over remote parts of the Pacific and Atlantic oceans.

The 8 April eclipse promises to be different: Roughly a third of its path of totality will stretch from southwestern Texas to northeastern Maine; major cities such as Dallas, Little Rock, Indianapolis, Cleveland, and Rochester are all within the path of totality.

Researchers and educators will once again eye the sky with eclipse-related projects.

The 50,000 Foot View

By the time the Moon’s shadow first reaches the United States in southern Texas at 1:27 p.m. CDT, a pair of WB-57 high-altitude research aircraft will have taken off from Ellington Field near Houston. After heading west and climbing to an altitude of roughly 15,000 meters (50,000 feet), they will intercept the Moon’s shadow just off the coast of Mazatlán, Mexico.

Amir Caspi, a solar astrophysicist at the Southwest Research Institute in Boulder, Colo., will travel to Texas to monitor one of the planes. Caspi is the principal investigator of a NASA-funded project that will use four cameras mounted on the aircraft’s nose to observe the Sun’s corona in visible and infrared light.

Heading high into the atmosphere on a maneuverable aircraft to observe a solar eclipse has many advantages. For starters, there’s no chance of being clouded out.

Heading high into the atmosphere on a maneuverable aircraft to observe a solar eclipse has many advantages, Caspi said. For starters, there’s no chance of being clouded out. “Clouds are the bane of every eclipse chaser’s existence,” he explained. The flights will also make it possible to record midinfrared wavelengths of light that would otherwise be absorbed and scattered by water molecules in the atmosphere. “It opens up wavelengths that you just can’t observe from below,” Caspi said.

Finally, because the WB-57 jets can literally chase the eclipse, their onboard instruments will be afforded a view of totality lasting roughly 6 minutes and 20 seconds—about 50% longer than that of stationary observers on the ground.

Caspi and his colleagues hope their data will shed light not only on the enduring question of why the Sun’s corona is so much hotter than the photosphere but also on why certain solar features known as prominences glow so brightly at midinfrared wavelengths.

After leaving Texas, the Moon’s shadow will skirt across the southeastern corner of Oklahoma before heading into Arkansas at 1:45 p.m. CDT.

When that happens, Ross Carroll and his team will be ready. Carroll, a physicist at Arkansas State University in Jonesboro, and a cohort of undergraduate students are taking part in the Nationwide Eclipse Ballooning Project, a NASA-sponsored effort involving hundreds of amateur scientists spread across the path of totality.

On 8 April, Carroll’s team will inflate a large latex balloon with helium, connect an instrument payload, and release it near the city of Paris, Ark. The balloon will rise at a rate of about 300 meters (1,000 feet) per minute and, if all goes according to plan, hover at an altitude of roughly 26,000 meters (85,000 feet) as it intercepts the Moon’s shadow. “That gives us a nice vantage point,” Carroll said.

Another Arkansas State University team will be waiting downwind on Petit Jean Mountain at a ground station equipped with four radio antennas. Those antennas will receive not only a live video feed from the stratosphere but also precise location, temperature, pressure, and humidity data collected by the balloon’s instruments.

One goal is to detect whether the passage of the Moon’s shadow affects gravity waves in the atmosphere. Measuring slight changes in the undulations of a floating balloon could help answer that question, Carroll said.

Stationary Snapshots

At 1:53 p.m. CDT, the Moon’s umbral shadow will enter Missouri. Shannon Babb, an aerospace educator working with the Civil Air Patrol, an auxiliary of the U.S. Air Force, will be waiting.

“They really loved the fact that they got to work together on a continent-sized group project.”

Babb is helping to coordinate several teams of Civil Air Patrol cadets in collecting solar eclipse data in Missouri and neighboring Illinois. The cadets, who range in age from 12 to 21, will take measurements of air temperature, wind speed and direction, and cloud cover during the eclipse. Those data will support GLOBE Observer, a network of amateur and professional scientists focused on collecting a wide variety of data about our planet.

The cadets will enter their data into an eclipse-focused GLOBE Observer app, and their observations will be aggregated with other data collected across the United States to better understand how eclipses affect the natural environment. Many of these young people also collected data during the 14 October 2023 annular solar eclipse, Babb said, and they’re looking forward to doing it again. “They really loved the fact that they got to work together on a continent-sized group project.”

Babb will also oversee teams of Civil Air Patrol cadets measuring how well very high frequency (VHF) radio waves propagate during the eclipse. First responders and search-and-rescue teams typically make use of those radio frequencies, which range from 30 to 300 megahertz, Babb said, but it’s relatively unknown how those kinds of radio waves are affected by the changes in Earth’s ionosphere that occur during an eclipse.

“There was anecdotal evidence that solar eclipses affected these radios in addition to the longer-band radios that have been really well studied,” Babb said. Pairs of cadets using VHF radios will investigate how their radio transmissions change, if at all, during the eclipse.

Long before the Moon’s shadow races across the very western corner of Tennessee and enters Kentucky at 1:58 p.m. CDT, Gordon Emslie will have made sure that his cell phone is charged. Emslie, a solar physicist at Western Kentucky University in Bowling Green, is the principal investigator of SunSketcher.

This project encourages members of the public to use their smartphones to take a preprogrammed set of photographs of the Sun during totality. The goal is to image brief flashes of light caused by sunlight streaming through lunar valleys. Photographs of these so-called Baily’s beads—named for a 19th-century British astronomer—can be combined with detailed information about the Moon’s topography known from Lunar Reconnaissance Orbiter observations to infer the precise shape of the Sun.

“Whether the beads appear depends on how big the Sun is,” Emslie said. The Sun’s exact shape in turn depends on its internal structure and magnetic fields. Emslie hopes that data from tens of thousands of SunSketcher participants will constrain the roundness of the Sun to better than about 5 kilometers. That would significantly improve current estimates of the Sun’s shape, he said.

Watching the Waves

After passing over Indiana, the Moon’s shadow will reach Ohio at 3:08 p.m. EDT.

Even if it’s cloudy in the Buckeye State that day, John Blasing, an amateur physicist and a member of the Cincinnati Astronomical Society, will be collecting data. That’s because he’ll record radio waves, which travel through clouds just fine.

Blasing is working with Radio JOVE Project 2.0, which encourages participants to build their own radio antenna and use it to observe celestial bodies such as Jupiter and the Sun. The project sells kits that include a radio receiver, the supplies to erect an antenna, and software to process signals over a frequency range of roughly 16–24 megahertz. Setting up a radio observatory is a fun project that combines astronomy with physics and engineering, Blasing said. “There’s a bit of cutting and fitting and soldering to do.”

On the day of the eclipse, Blasing’s radio telescope will record radio waves produced by both the Sun and the Milky Way.

On the day of the eclipse, Blasing’s radio telescope in the Cincinnati suburb of Cleves will record radio waves produced by both the Sun and the Milky Way. Comparing the intensities of those signals with data collected at other times will make it possible to study the effects of the eclipse on Earth’s ionosphere, Chuck Higgins, a founding member of the original Radio JOVE Project, reported at AGU’s Annual Meeting 2023 in San Francisco.

Ham radio operators are another group of radio aficionados getting involved in eclipse observations. To become a licensed ham radio operator in the United States, individuals must pass a test demonstrating knowledge about electrical engineering and space physics, among other fields. They’re a ready-made cohort of amateur scientists, said Nathaniel Frissell, a space physicist at the University of Scranton in Pennsylvania.

Frissell, whose call sign is W2NAF, said that he hopes that thousands of ham radio operators will be ready when the Moon’s shadow enters Pennsylvania at 3:15 p.m. EDT. As the leader of the Ham Radio Science Citizen Investigation (HamSCI), Frissell coordinates crowdsourced science experiments involving radio observations. Several eclipse-related projects are being planned, including ones that build on observations made during the 21 August 2017 total solar eclipse and the 14 October 2023 annular solar eclipse.

“Every eclipse gives you a chance to see things slightly differently,” Frissell said.

The hope is that data from HamSCI’s participants will reveal small changes that occur in Earth’s ionosphere during so-called ingress and egress, when the Sun is only partially blocked by the Moon.

Inviting All

When the Moon’s shadow barrels into New York at 3:16 p.m. EDT, both Buffalo and Rochester will experience totality.

Dan Schneiderman, eclipse partnerships coordinator at the Rochester Museum & Science Center, has been busy helping to plan a plethora of eclipse-related activities for viewers in the Rochester area. There will be no shortage of opportunities to observe the event, Schneiderman said, because 50 local organizations have been designated community eclipse ambassadors and have each received 1,000 eclipse glasses and a telescope with a solar viewing filter, among other supplies.

“There’s this multisensory experience you can have.”

Schneiderman is also helping to publicize crowdsourced science opportunities. One is Eclipse Soundscapes, a NASA-funded project in which participants collect audio data and other multisensory observations of an eclipse. There’s more to an eclipse than just its visual impact, said Henry “Trae” Winter, one of the coleaders of the project based in Medford, Mass. “There’s this multisensory experience you can have.”

As part of the Eclipse Soundscapes team, an amateur scientist can record the sounds made by animals or changes in temperature that occur during the eclipse, Winter said.

The project is building on a much earlier study that measured how the behaviors and vocalizations of birds, mammals, insects, fish, and other animals changed during the total solar eclipse in 1932. One goal of Eclipse Soundscapes is to determine whether a minimum eclipse threshold—that is, the fraction of the Sun’s disk that’s blocked by the Moon—is necessary for animals to behave significantly differently.

LightSound is another eclipse-related crowdsourced science project that challenges its participants to think beyond visual observations. The project provides open-source plans to build devices that convert light intensity into sound; as light levels change during a solar eclipse, participants will hear tone changes. The roughly palm-sized LightSound device is intended to allow people who are blind or have low levels of vision to experience an eclipse. LightSound hopes to distribute 750 of the devices before the 8 April eclipse.

After passing through Vermont and New Hampshire, the Moon’s shadow will zoom across Maine beginning at 3:28 p.m. EDT.

Shawn Laatsch, director of the Versant Power Astronomy Center at the University of Maine in Orono, is helping to coordinate people involved in the Citizen Continental America Telescopic Eclipse (CATE) 2024 project. The effort, which builds on a similar project conducted around the 2017 total solar eclipse, is looking to place roughly 35 telescopes along the path of totality to observe the Sun’s corona in polarized light.

Participating in science is a valuable way to cement what is already an awe-inspiring experience.

One specific goal is to better understand the so-called middle corona, the portion of the Sun’s outermost atmosphere that begins roughly 700,000 kilometers (435,000 miles) beyond the Sun’s surface and extends for about 4,000,000 kilometers (2,500,000 miles). Having observations from multiple vantage points along the path of totality will make it possible to construct 3D images of the middle corona, the team hopes.

After leaving Maine, the Moon’s shadow will race across eastern Canada and out over the Atlantic Ocean; the entire event will last about 2.5 hours. Researchers and educators alike hope that amateur scientists will embrace the opportunity not only to partake in a special event but also to collect scientifically important data.

Participating in science is a valuable way to cement what is already an awe-inspiring experience, Laatsch said. “Hopefully, it’ll inspire them to go further in astronomy.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2024), Eclipse science along the path of totality, Eos, 105, https://doi.org/10.1029/2024EO240135. Published on 26 March 2024.

Text © 2024. The authors. CC BY-NC-ND 3.0
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