For most Americans in the path of totality, Aug. 21 was spent in awe of the first transcontinental solar eclipse in 40 years. For the scientists and volunteers at the National Science Foundation (NSF) National Solar Observatory (NSO) Citizen CATE (Continental-America Telescopic Eclipse) project, the 90-minute eclipse event meant participating in a historic science experiment. The project is the first to collect research-quality observations of the sun’s corona during the transit across the United States, the longest data set of its kind.

“This dataset is extraordinary,” said Matt Penn, principal investigator for the project. “Normally during a solar eclipse, we get about 2 minutes of data in the region closest to the photosphere [solar surface]. But Citizen CATE allowed us to get an hour and a half of data.”

With support from NSF and other sources, the Citizen CATE experiment recruited hundreds of scientists, students and volunteers to track the sun along the path of totality with identical telescopes, software and instrument packages. Collectively, the 68 sites produced more than 4,000 images, some of which the NSO researchers used to compile the first-look video.

“The 2017 solar eclipse was more than an opportunity to marvel at the beauty of our nearest star; it was a chance to capture unique science,” said NSF Director France Córdova. “Working with more than 100 citizen scientists across the nation, NSF’s National Solar Observatory captured a continuous video of the eclipse as it passed over our country. I was pleased to be in Glendo, Wyoming, one of the Citizen CATE sites.”

Work started during the partial phase of the eclipse. In a carefully choreographed cosmic relay race, each Citizen CATE observer started observations when the shadow appeared on their horizon. With observers spaced an average of 50 miles from each other, each was ready and waiting to take the baton as totality passed over their local sky.

“Our teams had a great day! We had clear conditions at 58 of our 68 sites, and 48 sites have uploaded data so far,” Penn said. “We have produced a first-look movie of our data using 25 frames, less than 1 percent of what we gathered across all of our sites today. This preview spans from coast to coast, and gives us just a taste of what we can expect in the coming weeks. It can’t be used for science purposes yet, but it does provide an interesting preview about what we will see in our data. In the south and north we see polar plumes extending from the surface of the sun to the edge of the images. On the left side of the frame, we see a very bright coronal streamer, and the right-hand side shows a bright prominence.”

The full, high-resolution dataset, consisting of more than 4,000 highly processed images spanning the entire path of totality, will be assembled in the coming weeks with help from site volunteers and state coordinators.

“This dataset will allow us to see unprecedented views of our star’s inner atmosphere,” Penn said. “The plan is that our first papers will be led by our undergraduate researchers on the team.”

“NSF congratulates Matt Penn, the NSO, and the entire Citizen CATE project team on this great success,” said David Boboltz, NSF program director for NSO. “Citizen CATE will provide roughly 90 minutes of continuous observations allowing scientists to study the detailed dynamics of the inner solar corona, a place where many of the phenomena collectively known as space weather are thought to originate.”

Although the project is led by NSO, execution of the Citizen CATE experiment depended heavily on the unwavering dedication and enthusiasm of more than 100 volunteers. Each state had up to a dozen sites, all under the
guardianship of a state coordinator. Each individual site was the responsibility of the site leaders, who include amateur astronomers and school teachers.

“At our sites, we hosted tens of thousands of members of the public,” Penn said. “We are grateful for all of the interest, and hope that the support for the CATE project continues as our teams investigate other citizen science programs in astronomy.”

Solar eclipses occur about once every 18 months. They can occur at nearly any location on Earth as the moon slides between the Earth and sun, blotting out the sun’s light. The next total solar eclipse in the United States will occur on April 8, 2024. The path of totality in 2024 will enter the U.S. from Mexico into Texas and exit via Maine.

The CATE experiment is funded by a combination of federal, corporate and private sources, including several companies that donated equipment. This funding has meant that all the CATE equipment will be donated to volunteer observers or the schools at which they work after the eclipse.

“The equipment will be used by the teams for research, education, and public outreach efforts,” said Claire Raftery, head of education and public outreach for NSO. “We hope that this will go a long way to creating a lasting legacy of astronomy and solar science across the nation.”

The CATE team acknowledges the support of NSF, NASA, MathWorks, Daystar Filters, Celestron, Color Maker, the Research Corporation for Science Advancement, and others.

The movie is available for viewing at the Citizen CATE webpage.

NSO is run by the Association of Universities for Research in Astronomy (AURA) though a cooperative agreement with NSF.