“During the August 21, 2017, solar eclipse, our dozens of telescopes and electronic cameras collected data during the rare two minutes at which we could see and study the Sun’s outer atmosphere, the corona,” reported solar astronomer Jay Pasachoff to the American Astronomical Society, meeting in Denver during June 4-7. Pasachoff, Field Memorial Professor of Astronomy at Williams College, discussed results from his team’s observations made in Salem, Oregon, and measurements that his team has made of extremely rapid motions in the corona.
“We could see giant streamers coming out of low solar latitudes as well as plumes out of the Sun’s north and south poles, all held in their beautiful shapes by the Sun’s magnetic field,” he said. “In the months since the eclipse, we have used computers to pick out the best part of dozens of the images to make extremely high-contrast images that allow us to measure motions at extremely high speeds in the corona, as we compare our composite images with some made by coordinated colleagues 65 minutes farther east along the path of totality.” The motions reach hundreds of miles per second, thousands of times faster than normal terrestrial speeds.
The Williams College series of expeditions has also been studying how the corona changes over the 11-year sunspot cycle, which is now approaching its minimum. As a result, the coronal streamers that extend millions of miles into space are located only near the Sun’s equator, and thin plumes of gas extend north and south of the solar disk, as though there was a giant bar magnet in it guiding iron filings. The last time the team had such a good view of the polar plumes was at an eclipse viewed from Russia 10 years ago and at an eclipse viewed from China 9 years ago.
The Williams College team’s main observations were to study the solar corona, which is a million times fainter than the everyday Sun and normally hidden behind the blue sky. “Only at a total solar eclipse, when the blue sky goes away because normal sunlight is hidden by the Moon, can we see the corona at all this well. And because the Sun’s magnetic field changes over the 11-year sunspot cycle and erratically as well, each time we look at the corona — even when we get only a couple of minutes to see it every couple of years somewhere in the world — we have a new Sun to study, just as a cardiologist-researcher who looked inside someone’s heart in, say, Africa two years ago for a couple of minutes would still have lots to learn by looking at a new patient in the U.S. a couple of years later.”
“We are learning about the Sun’s influence on the Earth,” said Pasachoff, “which we now call space weather. Eruptions on the Sun can zap and kill satellites in Earth orbit and even cause surges on power lines and blackouts. We want to understand how to predict and monitor solar eruptions that affect us on Earth, and observations during our rare opportunities at total solar eclipses contribute to these goals.”
Along with an international team of professional colleagues, eight William College undergraduates as well as several recent alumni graduate students and Ph.D.s participated, many programming and operating computer-controlled cameras to record the event. All are coauthors of the iPoster available at this week’s AAS meeting.
In Oregon last summer, Pasachoff viewed his 66th solar eclipse. He serves as Chair of the International Astronomical Union’s Working Group on Solar Eclipses, and as such helped coordinate scientific colleagues’ visits to the U.S. for eclipse observing from, among other countries, China, Japan, Venezuela, Bulgaria, Greece, Poland, and Slovakia.
Pasachoff’s observing team had the advantage of a research grant awarded four years ago by the Committee for Research and Exploration of the National Geographic Society. For the 2017 total solar eclipse, his scientific capabilities then expanded with the award of a major research grant from the Solar Terrestrial Program of the Atmospheric and Geospace Sciences Division of the U.S. National Science Foundation.
With these grants, the Williams College Expedition supported such scientists as Ronald Dantowitz of the Clay Center Observatory of the Dexter Southfield School in Brookline, Mass.; Vojtech Rusin of the Astronomical Institute of the Slovak Academy of Sciences in Tatranská Lomnica, Slovakia; John Seiradakis and Aris Voulgaris of the Aristotle University of Thessaloniki, Greece; Marcos Peñaloza-Murillo of the University of the Andes in Merida, Venezuela; and Michael Person of MIT; and had additional collaboration with Amanda Bosh and Stephen Levine of MIT and the Lowell Observatory and Marek Demianski of the University of Warsaw, Poland. Williams College astrophysics alumni experienced from past eclipse expeditions who participated in the observing include Daniel Seaton of the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado in Boulder; and graduate students Muzhou Lu of the University of Colorado in Boulder; and Allen Davis of Yale. Graduate student David Sliski o
f the University of Pennsylvania also made significant contributions to the research effort. They observed from platforms on the Willamette campus that provided electricity and internet to aid in the telescopes’ tracking and the electronic-cameras’ data-collecting abilities. They were joined in the scientific work by eight Williams College undergraduates: Ross Yu ‘19 of Huntington Beach, Calif.; Cielo Perez ‘19 of Dallas, Texas; Erin Meadors ‘20 of Albuquerque, N.M.; Christian Lockwood ‘20 of Quogue, Long Island, N.Y.; Charles Ide ‘20 of Natick, Mass.; Declan Daly ‘20 of Seattle, Wash.; Brendan Rosseau ‘19 of Glen Ellyn, Ill.; and Connor Marti ‘20 of Cranford, N.J. The first four are analyzing eclipse data during the summer of 2018 and two are continuing with senior theses. Aram Friedman of Ansible Technology in Princeton, N.J., coordinated wide-field video observations, including a 360° video. Four of the students were supported by Pasachoff’s NSF grant; others received funds from the NASA Massachusetts Space Grant Consortium, Sigma Xi (the honorary scientific society), the Clare Booth Luce Foundation, and Williams College, including the Freeman Foote Expeditionary Fund. The Salem-based expedition coordinated measurements of velocities with a team of scientists in southern Illinois headed by Thanasis Economou of the University of Chicago.
Pasachoff worked closely over several months with the NOVA program on PBS, which pushed through a revised final 20 minutes of their hour-long show, “Eclipse Over America,” at 9 p.m. on eclipse night, with a revised version airing two nights later and an international edition now in circulation.
One of the main scientific conundrums that the team tackled is the cause of the heating of the solar corona to millions of degrees. The scientists operated special fast cameras that have negligible dead time between high-quality frames, using the POETS (Portable Occultation, Eclipse, and Transit System) devices that were purchased a dozen years ago jointly by MIT’s occultation-research group and Williams College with a NASA equipment grant. The data were successfully recorded and are being analyzed.
In collaboration with NASA’s Goddard Space Flight Center (Greenbelt, Md.), a combination of space observations at the time of the eclipse with the Williams team’s composite images emphasizing coronal structure was released by NASA at https://www.nasa.gov/image-
Pasachoff also works with atmospheric scientists Marcos Peñaloza-Murillo from Venezuela, who had been a Fulbright Fellow at Williams College six years ago, and Michael Thomas Roman of the University of Michigan to understand the effect of the abrupt shutting off of incident sunlight by the onset of totality on Earth’s wind, temperature, pressure, and other weather aspects.
Several other scientists joined Pasachoff at his site to view the fantastic spectacle, often accompanied by family members. They included David Hathaway, retired NASA expert on the sunspot cycle; Susan McKenna-Lawlor of Maynooth University in Ireland (who mistakenly flew to Portland, Maine, instead of Portland, Ore., but nevertheless managed to reach Salem, Ore., in time for the eclipse); Deepto Chakrabarty of MIT; Robert Vanderbei of Princeton; Ruslan Belikov of NASA’s Ames Research Center; Edw. Ginsberg of the University of Massachusetts at Boston; John Briggs of his private observatory in New Mexico; and Phyllis Lugger of the University of Indiana. Douglas George of Cyanogen Productions Inc. in Toronto, provided a set of electronic cameras; and R.J. Smith of Bisque, Inc., of Colorado, a provider of high-quality tracking telescope mounts and control software, were also part of the expedition. Alan Sliski of Lincoln, Mass., lent his expertise on telescope mounts and on cameras for eclipse use. Williams College alumni with Ph.D. degrees attending included Joey Shapiro Key of the University of Washington at Bothell; Kristen Shapiro Griffin of Northrop Grumman; and with National Science Foundation support; Duane Lee of Vanderbilt University and Marcus Freeman, as well as University of Maryland graduate student in astronomy Amy Steele. Also on site were 10 Japanese astronomers with 40 of their colleagues coordinated between Pasachoff and Hiroki Kurokawa of the Kwasan Observatory, Kyoto University; and nearby — in Dallas, Ore. — were 25 Chinese astronomers headed by Zhongquan Qu of the Yunnan Observatory, China.
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