Small-scale astronomers had recognized her work for quite some time, but it took many years for Hisako Koyama’s name to become renowned in the profession science community. A recently published paper outlines how her work impacted the documentation of sunspots over the last century.
Koyama used the same Nikon 20-cm telescope, gifted to her by her father in her 20s, throughout the course of her life to create more than 10,000 sunspot sketches. //Kawade Shobo Shinsha Publishers
Koyama’s name lingered in the back of Delores Knipp’s mind for years before she decided to conduct a detailed study on her work, outlined in the American Geophysical Union journal, Space Weather. Knipp, a space weather scientist at the University of Colorado Boulder, first caught sight of Koyama at a lecture given by Leif Svalgaard, a solar scientist. Svalgaard was discussing a recent effort by international scientists to create a complete timeline of sunspot observances, dating back to 1610, called the sunspot reconstruction project. She displayed a photo of Koyama crouching next to her telescope, and explained how her sunspot sketches closed the early 20th century gap in sunspot documentation, ultimately providing the vital records needed to complete the project.
"I was astounded; I'd never seen a major observational solar record from a woman," Knipp said in a press release. "It stuck in my mind, and I wondered why I hadn't heard of her."
Koyama’s accomplishments loomed in Knipp’s head for two years before an unexpected source gave her the inspiration she needed to finally research her work: the 2016 film Hidden Figures, which follows three female, African-American NASA scientists.
"I was so taken and inspired by that, and even though I had been thinking about it before, the 'Hidden Figures' movie was the thing that pushed me into gear, and I said, 'I've got to know more about this record from Japan,'" Knipp said.
With motivation kicked into high gear, Knipp commissioned space scientist, Huixin Liu, of the Kyushu University in Fukuoka, Japan, and historical researcher Hisashi Hayakawa, of the Japan Society for the Promotion of Science in Tokyo, to help her carry out the study. Together, they compiled information that outlined the work of, arguably, the greatest sunspot observer of the 20th century.
Koyama, born in Japan in 1916, showed an interest in astronomy from a young age. Though she didn’t have any formal training in science beyond her high school education, she began surveying and illustrating sunspots in 1944, with a refracting telescope that was given to her by her father.
Sunspots represent areas of the Sun with increased magnetic activity, lowering the Sun’s surface temperature in that area and creating a short-term dark spot. Though sunspots appear sporadically and the number of them fluctuate with each of the Sun’s 11-year solar cycles, they can be used to track changes in the Sun’s magnetic activity and give scientists an idea of how the changes may impact conditions on Earth.
In 1944, the same year she began observing sunspots, she submitted one of her sketches to Japan's Oriental Astronomical Association, and received positive feedback from Issei Yamamoto, OAA’s solar section president. With direction and insight from Yamamoto, Koyama continued to contribute consistent sunspot sketches, noting any significant details of solar activity, to the Tokyo Science Museum, now known as Tokyo's National Museum of Nature and Science. The museum hired Koyama on as a staff observer that same year.
Koyama spent her career at the museum, documenting and sketching sunspots until her retirement in 1981. All the while, she used the same telescope gifted to her by her father decades earlier. She continued to record sunspots as a museum fellow following her retirement, and died in 1997. Over the course of her life, she created more than 10,000 sketches of Sun activity.