Photo of Hisako Koyama taken in 1951 (via Wikimedia Commons)

 

Life and Work

Hisako Koyama was born in 1916 in Tokyo, then already one of Japan’s major urban centres. Her parents were clearly supportive of her education and interests, since Hisako graduated from the prestigious Tokyo high school for girls, and her father later gifted her the telescope she would use to make her first sunspot observations. ¹

Witnessing a shooting star sparked Hisako’s interest in astronomy. She began her professional pursuit in the early 1940s after reading several astronomy books including a telescope-making guide. During city-wide power cuts in World War II, Hisako would starwatch from her yard with her starcharts and a small flashlight in hand. Her first achievement was assembling her own telescope with the help of a telescope shopkeeper after a visit to the Tonichi Planetarium. By spring 1944, she was making sunspot observations with the 36mm by 60 refractor telescope (3cm refractor telescope) from her father. ²

Hisako initially wanted to join the Moon section of Japan’s Oriental Astronomical Association (OAA) in 1944, but did not have the right telescope for it, thus she began observing the sun. She was able to get her first sunspot sketch after one month, which she sent to the OAA solar section president Issei Yamamoto. Yamamoto’s response validating that, “yes, they are sunspots,” encouraged Hisako to pursue a full blown career in solar observations. ³

From 1945-1946, Hisako trained under Yamamoto to perform “attenuated direct viewing” using her 3cm refractor telescope, where she looked through the eyepiece directly to make sketches. She attended her first Japan Society for Astronomical Studies meeting at the National Museum of Nature and Science (NMNS) in late 1945 and became an official staff member and observer the following year. From 1946 onwards until her retirement from NMNS, she used the same 20cm refractor telescope where she would use its projection function to observe and sketch sunspots.⁴

Hisako made over 10,000 sunspot sketches throughout her life. She observed twice a day at one hour intervals, through extreme temperatures and bad weather. By 1964, she had created a butterfly sunspot diagram (showing changes in latitudes of sunspot groups over solar rotations) with an impressive 3 ½  butterflies consisting of data she recorded over 17 years, as seen in Figure 1. Most notably, she made a sketch of the largest sunspot in the 20th century in April 1947. She also detected and sketched the white-light flares of November 15 1960. Her 50 volumes of personal log books provided “one of the best reference series for the second part of the 20th century” on account of their longevity and consistency. ⁵ During the Zürich era before 1980, when sunspot data was almost exclusively collected from the Swiss Federal Observatory, 40 external stations’ data were occasionally used for periods of bad weather at the Zürich station – Koyama was one of the 40. She also posted monthly reports to the Royal Observatory of Belgium. ⁶ Her data was also used for the later recalibrated International Sunspot Number (ISN) by the Solar Influences Data Analysis Centre (SIDC). ⁷

Hisako often performed her observations publicly at the NMNS as part of her “outreach” position at the museum, demonstrating her equipment as well as explaining the astronomy behind the phenomena she was observing to visitors, including many children. She also organised many public events, including sky watching almost every Saturday, a seminar on constellations every month, and observation campaigns during eclipses, close approaches of other planets and planetary conjunctions. She wrote about some of such events in her frequent astronomy columns and accounts. Her entry on the observation campaign for the July 1963 solar eclipse showed that 40 ametur astronomers and 700 visitors were able to observe the “inner corona, prominence and diamond ring” under Hisako’s guidance. ⁸ Her contributions to the public-facing sides of the NMNS and OAA were also acknowledged by her peers in professional observing. Former director of the OAA’s Jupiter-Saturn section Takeshi Sato once praised Hisako’s organisational role in the 1972 Jupiter Observers’ Conference, along with noting that “she is a sunspot observer of great renown.” She also received the OAA Prize of Encouragement of Academic Research in 1986. ⁹

Apart from physical outreach, Hisako disseminated her knowledge through numerous publications. She published first sunspot observation book including description on how to count sunspots in 1949, and later an article of “Additional notes on how to count sunspot numbers” in 1965, after more years of experience and discussions with fellow experts like Max Weildmeirer from the Swiss Federal Observatory. She published articles and reports for the Astronomical Herald between 1967-1989, even after her retirement from NMNS. In 1981, after her retirement from NMNS, she wrote a memoir that covered her work over the past 35 years. She also published a monograph called “Observations of Sunspots”, where she published the over 8000 sunspot groups she categorised. ¹⁰

 

Hisko Koyama’s 50-year sunspot observational record was not formally celebrated until 2004, when the Japanese National Geographic published an article about her titled “Hisako Koyama, who left more than 10000 detailed sketches.” In 2012, a Minor Planet was renamed “3383Koyama” in honour of her at the proposal of another OAA member. ¹¹

 

Experience as a Pioneering Japanese woman in STEM and Astronomy

Hisako Koyama has been described as an “unusual woman of her time”. Firstly she had parents, especially her father, who supported her interest in astronomy and made sure she had a good education. Secondly, her career development as a scientist had been unconventional, taking the leap as a self-taught amateur to join professionals in the field. Finally, she linked the professional and public worlds between which she herself had to cross to become a scientist, educating and encouraging interest through interaction and writing. Undoubtedly these factors are connected, it is only with her privileged and non-conservative family background that she had the capacity and nerve to take such risks in her career, yet her pioneering actions placed her in a precarious position in the patriarchal field. ¹² Although the tremendous qualitative and quantitative value of Hisako’s work go mostly unacknowledged by academics, her connection with the common people must have left a lasting impression. 

 

Bibliography

Hayakawa, Hisashi, Frédéric Clette, Toshihiro Horaguchi, Tomoya Iju, Delores J. Knipp, Huixin Liu, and Takashi Nakajima. “Sunspot observations by Hisako Koyama: 1945–1996.” Monthly Notices of the Royal Astronomical Society 492, no. 3 (2019), 4513-4527. doi:10.1093/mnras/stz3345.

Knipp, D., Liu, H., & Hayakawa, H. (2017). Ms. Hisako Koyama: From amateur astronomer to long-term solar observer. Space Weather, 15, 1215–1221. https://doi-org.ezproxy.wellesley.edu/10.1002/2017SW001704.