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  • Writer's pictureDale DeBakcsy

One Life for the Sun: Hisako Koyama’s Half Century of Solar Observation.

If anybody embodies the spirit of Helen Sawyer Hogg’s mantra that The Stars Are For Everybody, it is Hisako Koyama (1916–1997), who built a multi-decade career of profound astronomical significance without a university education or the mass of observational artillery we usually associate with Twentieth Century astronomy. Instead, she found a subject she was passionate about, that she could study with generally accessible equipment, and stuck to her self-proclaimed task twice a day, every day, for nearly a half century, ultimately producing a body of data so uniform and reliable that it was chosen as her time’s representative data set to stitch into a series of observations stretching backwards in time all the way to Galileo himself.

Koyama was born in 1916 into an urban Japanese family. At that time, thanks to educational reforms begun in the Meiji Era (1868–1912), education in Japan was in the midst of adopting Western models, with Tokyo Imperial University founded in 1877, followed in 1911 by the founding of the first co-educational college, Tohoku Imperial University, which opened its doors to women in 1913. Prior to that, women in Japan had no access to higher education, and in fact rarely were educated past middle school. In 1910, for example, of the roughly 3 million girls who attended primary school, only 56,000 went on to middle school, while of the 3.3 million boys in primary school, more than twice as many, or 122,000, went on to middle school. Fortunately, by Koyama’s time, women’s middle and high school education was significantly on the rise, and in 1935 there were actually more girls in middle school (412,000) than boys (341,000), though a significant part of that trend might have been more due to a curriculum change that taught girls sewing methods that were perceived by parents as useful in their future domestic lives, than a desire for women’s academic advancement.

It was in the middle of this boom in girls’ education that Koyama graduated from a Tokyo girls’ high school, sometime in the 1930s. Her options at that point for continuing education were highly limited. She could have attended Tohoku, but it was located some 225 miles to the northwest of her family’s home in Tokyo, which would have been an unthinkable distance for most families to send a daughter away by herself in that time. She could have taken the path pioneered by Tsuda Umeko, who went to the United States to attend Bryn Mawr college in 1899, but that was even more unlikely from a familial perspective than Tohoku. What might have been more acceptable was to attend the Tokyo Women’s Normal School, established in 1875 (and still in existence as Ochanomizu University) as a training school for future teachers. The location was right, but the purpose was not. Though Koyama would later become one of Japan’s leading lights for public outreach and education, she did not have any professed inclination at that time to become a teacher.

So, she rested content with her high school diploma, and threw herself into a private study of the thing that interested her the most: the stars. She bought and devoured books on astronomy, spent nights outside observing the sky with the help of astronomical charts and, after a visit to Tokyo’s Tanichi Planetarium, resolved to make her own telescope, which she did with the help of an obliging telescope vendor, who showed her how to grind her own lenses. Later, her father purchased for her a 36mm refractor telescope, and it was this instrument that properly began her amateur astronomical career. There is a famous story of her, in the middle of the Tokyo blackouts during the end of the Second World War, dragging her futon out to the backyard so that she could sit under it with her star charts and take advantage of the sudden lack of city lights to properly observe the night sky, which is perhaps the most beautiful image of pure human curiosity that you’ll find in this entire book.

Her first desire was to make some useful observations of the moon, but her telescope wasn’t powerful enough she felt to do any work of lasting value to astronomy, so instead she turned it to the sun, allowing the focused image to fall onto a sheet of paper, which she could then observe and sketch without danger to her eyes (the first solar telescopic observer, Galileo Galilei, famously did look directly through his instrument at the sun on a few occasions, but took the precaution of doing so when the sun was lower in the sky, and preferably in the presence of fog, to place as much atmosphere between him and it as possible, which was a better idea than looking at it at, say, noon, but still not a great idea.) In 1944, she anxiously sent her first sketch of solar sunspots to the Oriental Astronomical Association’s Solar section, unsure of whether her independent efforts would be lauded or condescendingly scorned. The answer she received from the section’s president (and professor at Tokyo University), Issei Yamamoto, was positive, and for the next two years Koyama pressed on with her solar observations until, in 1946, she gained access to the 20 cm refractor telescope at the Tokyo Science Museum (today the National Museum of Nature and Science) after joining its staff.

(For my fellow American readers who refuse to think in metric for moral reasons, 20 cm is about 7.9 inches, meaning Koyama’s telescope was significantly smaller in aperture than the 12 inch Whitin telescope donated to Wellesley for undergraduate use nearly three decades previously.)

This 20 cm telescope would be Koyama’s primary observational tool for the next 41 years, until her full retirement in 1991. Every day, twice a day, for a period of about an hour each session, she would train her telescope on the sun and draw the details of the sunspots she observed. Now, you might be wondering to yourself, with such an important long-term project, and with the vast improvements in instrumentation that took place over those four decades, why was it that she persisted in using that 20 cm instrument from the war years? The reason lay precisely in the long-term nature of the project. To Koyama, and to the larger astronomical community, the continuity of instrument employed was one of the most important features of her work. By not upgrading her telescope every five years like some cosmic iPhone, she minimised the sources of variation in her observations, establishing a baseline of solar observation of unparalleled consistency.

Her first publication of her results in 1981, 35 Years with the 20cm Telescope, and its follow up volume, 1985’s Observations of Sunspots, 1947–1984, were treasure troves of information for solar astronomers, and particularly in the field of sunspot study. In this, she was carrying on the work of Annie and William Maunder, whose research in the early 20th century established the eleven year solar cycle, and led them to create the Maunder Butterfly Diagram to visualise the distribution of sunspots over time. Koyama’s work recorded three and a half of these cycles, which she with characteristic modesty would refer to as ‘only a blink for the sun’ but that at the time represented the longest sustained set of sunspot observations in human history. That work has sparked even larger efforts to document the sun’s past, including a 2014 effort to construct a continuous sunspot history dating back to 1610 which employed data from Galileo, through Gassendi, Schwabe, Wolf, and Maunder, and leaning heavily in the late Twentieth century on Koyama. Further, her observations of sunspot asymmetries (also a specialty of Annie Maunders) were used by Derek Swinson in his studies of cosmic ray densities in the sun.

Hisako Koyama was not just her era’s greatest sunspot observer, however (though that would certainly have been enough accomplishment for one lifetime), but was also one of NMNS’s most public representatives and advocates for amateur astronomy. When she wasn’t recording her impressions of the solar surface, she was out on the museum grounds, organising regular telescope viewing parties for the general public, or planning planetarium shows to highlight interesting, readily observable features of the night sky, or writing popular articles to engage as many people as possible in the act of looking skywards and understanding what they are seeing. As an amateur astronomer who had been warmly encouraged on her way, she made sure that she gave of her time, encouraging the rising generation (and the one after that) to not give up on their passion for the cosmos just because they didn’t have a multi million dollar apparatus at their disposal.

In 1981, Koyama retired from the NMNS, but continued her research as a Fellow of the Museum until 1991, when finally, after forty-seven years of continuous observation, she said good-bye to our sun at last, and headed off into the long sunset of her own life.


If you'd like to read more about women astronomers like Jill Tarter, check out my History of Women in Astronomy and Space Exploration, which you can order from Amazon, or from Pen and Sword US or UK.


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