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Sunspots imaged by NASA's Solar Dynamics Observatory (SDO). Each spot in the right of the image is over six Earths across. Credit: NASA/SDO/AIA/HMI/Goddard Space Flight Center

Star Stuff: Meet Hisako Koyama, Japan's queen of sunspots

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Star Stuff is a weekly column by rocket scientist & astrophysicist Summer Ash highlighting some amazing things happening every day on and off the planet, especially great science done by and/or for women. She harnesses her science communication powers to smash the patriarchy and advocate for equality and inclusion across all time and space. Throwdowns with pseudoscience may occur.


What’s the first thing that comes to mind when you hear the word “sunspots”? Is it Galileo? That song by The Police? Or maybe that thing that happens to your vision when you look directly at the sun (like you’re never supposed to do)? If it’s Galileo, we’re on the right track, but hopefully after today, it will be: Hisako Koyama.

 Koyama at the Tokyo Science Museum in 1951. Credit:  Asahigraph & Knipp, Liu, Hayakawa via Space Weather.

Thanks to a recent paper published in Space Weather, a journal of the American Geophysical Union, Hisako Koyama’s story is now being told among western astronomers. Born in Japan in 1916, Koyama began observing the Sun when she was 28 and when she died in 1997, she left behind roughly four decades of the most consistent and reliable records of sunspots ever produced.

Sunspots are transient phenomena observed on the photosphere, or surface, of the Sun. As their name suggests, they are regions that give off less light than the surrounding surface. They can appear and disappear, lasting days to months, and range in size from 10 miles in diameter up to 100,000 miles (0.001 to 10% the diameter of the Sun). More importantly, they come in cycles and correlate with magnetic activity such as solar flares and coronal mass ejections - two potential threats to our planet. For this reason, accurate historical records of our Sun’s past are vital to understanding and predicting its future.

Title page of Johann Fabricius's small pamphlet about sunspost published in 1611. Credit: Public domain.

Galileo tends to gets most of the sunspot spotlight, but Chinese astronomers knew about sunspots as far back as 364 BC and by the start of the first millennium, theywere regularly recording them. The first telescopic observations of sunspots in the West were made in 1611, not by Galileo, but by both English astronomer Thomas Harriot and father and son Frisian astronomers, David and Johannes Fabricius. In fact, Johannes Fabricius was the first to publish observations of sunspots in his 22 page pamphlet, De Maculis in Sole observatis. Galileo published his sunspot drawings two years later in 1613. He observed the Sun at the same time of day for 36 consecutive days, allowing him to track the motion of sunspot across the surface of the Sun and giving further evidence to Frabricius’s claim that the Sun rotated on its axis.

Animation of sunspot drawings by Galileo Galilei from Istoria e Dimostrazioni Intorno Alle Macchie Solari e Loro Accidenti Rome (History and Demonstrations Concerning Sunspots and their Properties) published 1613.

For more than 400 years, astronomers have continued to observe the Sun and record the coming and going of sunspots, searching for patterns and connections between them and our life here on Earth. And the more data we can take into account, the better. That’s where Hisako Koyama comes in.

Koyama graduated from an all-girls high school in Tokyo in the 1930s and was keen on astronomy from an early age. During the blackouts of World War II, instead of staying inside, she would camp out in her backyard with a star chart to study the heavens. Shortly before her thirtieth birthday, her father gave her a small refracting telescope. According to lead author Delores Knipp, a Professor of Aerospace Engineering Sciences at the University of Colorado at Boulder, Koyama had aspirations to join the Moon division of Japan’s Oriental Astronomical Association (OAA), but was informed her telescope wasn’t powerful enough for lunar observing. So she turned it to the Sun instead. Using the telescope as a pinhole camera, she projected an image of the Sun on a flat surface and began sketching sunspots. She eventually got up the courage to submit one of her drawings to the OAA. The president of the solar section at the time, Issei Yamamoto, responded with encouragement, so Koyama kept at it. A few years later, she was hired as a staff observer at the the Tokyo Science Museum (now the National Museum of Nature and Science) where she worked remained until her retirement in 1981 at the age of 65.

Koyama at the Nikon 20 cm refractor telescope she used for her daily observations at the Tokyo Science Museum. Credit: Knipp, Liu, Hayakawa via Space Weather.

During her tenure at the museum, Koyama came to work every day for nearly forty years to peer at the Sun’s surface and record what she saw. Each day that wasn’t foiled by weather, she produced a detailed sketch, taking note of precise times, locations, sizes, and shapes of the spots she observed. A drawing a day may not seem like much, but all her drawings taken together add up to more than 10,000 glimpses of the Sun, featuring over 8,000 unique sunspot groups. And they are an essential part of our 400+ year record of sunspot activity.

Sunspot drawing for April 5, 1947 featuring the largest sunspot group of the 20th century. Credit: Hisako Koyama

Knipp first learned about Koyama’s work when she attended a talk by Leif Svalgaard, a senior research scientist in the Hansen Experimental Physics Laboratory at Stanford University, on a project he was involved in attempting to reconstruct our modern solar data record from 1610 to the present. Svalgaard's team came across Koyama's drawings during their research and now use her data set as a "backbone" of their reconstruction effort. The moment stuck with Knipp because she had never heard of any significant solar observations of this type done by a woman. European men like Galileo, Pierre Gassendi, Johann Caspar Studacher, Heinrich Schwabe, and Rudolf Wolf dominated when it came to sunspot records. Months later, as Knipp, was watching “Hidden Figures,” Koyama’s name popped back into her mind and she immediately set out to learn more.

Knipp connected with Huixin Liu, a space scientist at Kyushu University in Fukuoka, Japan, and Hisashi Hayakawa, a historical research fellow at the Japan Society for the Promotion of Science in Tokyo to dig into Koyama’s history and all three soon realized it was a story that needed to be told. In additional to Koyama’s vital scientific contributions, her life and career are proof that non-European men, not to mention women, were active in the field of astronomy at a time when recorded history was oblivious to their existence. The more they learned about Koyama’s story, the more amazing she became. Not only did she obtain a high school education when that was far from the expected path for a girl in Japan at the time, but she transitioned into her full-time job without an advance degree.

Today we would classify Koyama as an amateur astronomer, but she seems to have straddled the gap between amateur and professional, never being academically trained in solar physics but making fundamental contributions to the field all the same. Outside of her prescribed work, Koyama was dedicated to education and outreach. She organized events, classes, and seminars to share her love of astronomy and her knowledge of the Sun with everyone who asked. Even after she retired, she continued to visit the museum and interact with museum-goers. Koyama’s work helped to highlight amateur astronomy and citizen science in Japan. There’s no way to know how many young girls she may have inspired in her own country, but it’s clear young girls in all countries need to hear her story. Knipp, Liu, and Hayakawa hope to help that happen by spreading the word to the broader astronomical community.

If you’re like me and you love data and old drawing and old drawings that actually consist of data, check out Koyama’s full archive here. The page will load in Japanese, but hit ‘translate’ and then you can search by either sunspot number or sunspot group. Once you’ve chosen the drop down menus up top (shown in Japanese) will switch to roman numerals once you click and you can then select year and month. Finally, click the orange button on the left column of the resulting table to view the images and swoon your geeky heart out.

Believe it or not, astronomers are still recording sunspots by hand. At the Mount Wilson Observatory atop the San Gabriel Mountains, just outside Pasadena, California, the 150-Foot Solar Tower has been in continuous operation since 1912. You can check in here on any give day to see the latest sunspot drawing. 

Want to learn to sketch sunspots yourself? Sky & Telescope has you covered. Once you have enough practice, you can even submit your drawings to the Solar Section of the Association of Lunar and Planetary Observers and maybe even be the Hisako Koyama of the 21st century.