“During World War II, Tokyo often held drills to prepare citizens for airstrikes. But when the sirens blared and blackouts hit the city, a young Hisako Koyama would sneak back outside with her futon in one hand and a star chart in the other...”  [PBS NewsHour]

Japanese astronomer and “hidden figure” Hisako Koyama (1916-1997) drew the spots on the sun’s surface, every day for 40 years. Her archive of 10,000 sunspot sketches was a historic milestone in solar science. A woman with no formal scientific education, Hisako quietly flaunted 20th-century Japanese social conventions as she rose to international prominence.

What is a sunspot?

A sunspot looks like a dark spot on the surface of the sun. It’s a region where the sun is cooler than usual, due to the strength of its magnetic field. Sunspots are constantly moving and growing (the average sunspot is about the size of planet Earth!).

Image by The Royal Swedish Academy of Sciences/The Institute for Solar Physics

Why do sunspots matter?

When sunspots are more active, the result is a spike in the Earth’s geomagnetic storm activity, which can disrupt power grids and satellites.

Radar, radio, television, the internet, GPS, weather forecasts, and more… All our electronic methods of communication, research, and navigation hinge on our understanding of the sun.

Why was Hisako’s work important?

Hisako’s work helps us understand the solar cycle, an 11-year-long pattern in which sunspots form, move, and dissolve. Over her lifetime, she fully documented an astounding three and a half solar cycles!

Hisako Koyama observed the largest sunspot of the 20th century on April 5th, 1947. The collection above shows her drawings from the weeks surrounding that date. Images by the National Museum of Nature and Science in Tokyo.

Recently, scientists reconstructed the history of sunspots from the 1610s to the early 2000s, using data from a handful of the best solar observers throughout history – including Galileo, Staudacher, Schwabe, and Hisako Koyama.

Hisako Koyama subverts our expectations of what science looks like. She reminds us how seemingly small acts can have an immense impact over time... through the power of observation and perseverance.