In the spring of 1944, Tokyo residents experienced numerous aerial attacks from Allied bombers. Air raid sirens warned citizens to get indoors and preceded strategic blackouts across the city. However, for 28-year old Hisako Koyama, these blackouts were opportunities. She would gaze at the night sky, tracking all sorts of astronomical phenomena, using a futon over her head for protection.
Her latest endeavor required the light of day. By angling her telescope towards the sun, Koyama could project the star’s light onto a sheet of paper, allowing her to sketch the sun’s shifting surface. She spent weeks recreating this setup, tracking every change she saw. Unbeknownst to her, these drawings were the start of one of the most important records of solar activity in human history.
To understand exactly what Koyama saw on the sun’s surface, we first need to understand what’s happening inside the star. Every second, trillions of hydrogen atoms fuse into helium atoms in a process called nuclear fusion. This ongoing explosion maintains the sun’s internal temperature of roughly 15 million degrees Celsius, which is more than enough energy to transform gas into churning pools of plasma. Plasma consists of charged particles that produce powerful magnetic fields. But unlike the stable charged particles that maintain magnetic activity on Earth, this plasma is constantly in flux, alternately disrupting and amplifying the sun’s magnetic field.
This ongoing movement can produce temporary concentrations of magnetic activity which inhibit the movement of molecules and in turn reduce heat in that area. And since regions with less heat generate less light, places with the strongest magnetic fields appear as dark spots scattered across the sun’s surface. These so-called sunspots are always moving, both as a result of plasma swirling within the sphere, and the sun’s rotation. Accurately counting sunspots and tracking their movement can be a challenge, depending greatly on the perception and judgment of the viewer. This is precisely where Koyama’s contributions would be so valuable.
Despite having no formal training in astronomy, her observations and sketches were remarkably accurate. After sending her work to the Oriental Astronomical Association, she received a letter of commendation for her dedicated and detailed observations. With their support, she began to visit the Tokyo Museum of Science, where she could use a far superior telescope to continue her work. Koyama soon joined the museum’s staff as a professional observer, and over the next 40 years, she worked on a daily basis, producing over 10,000 drawings of the sun’s surface.
Researchers already knew magnetic currents in the sun followed an 11 year cycle that moved sunspots in a butterfly shaped path over the star’s surface. But using Koyama’s record, they could precisely follow specific sunspots and clusters through that journey. This kind of detail offered a real-time indication of the sun’s magnetic activity, allowing scientists to track all kinds of solar phenomena, including volatile solar flares. These flares typically emanate from the vicinity of sunspots, and can travel all the way to Earth’s atmosphere. Here, they can create geomagnetic storms capable of disrupting long range communication and causing blackouts. Solar flares also pose a major risk to satellites and manned space stations, making them essential to predict and plan for.
During an interview in 1964, Koyama lamented that her 17 years of observation had barely been enough to produce a single butterfly record of the solar cycle. But by the end of her career, she’d drawn three and a half cycles—one of the longest records ever made. Better still, the quality of her drawings was so consistent, researchers used them as a baseline to reconstruct the past 400 years of sunspot activity from various historical sources. This project extends Koyama’s legacy far beyond her own lifetime, and proves that science is not built solely on astounding discoveries, but also on careful observation of the world around us.
Using a safe method to observe the sun, such as projecting its image onto a piece of paper, try to sketch the sunspots you see. Compare your sketches over a week to see how the sunspots move and change. This will help you understand the process Hisako Koyama used and appreciate the detail and dedication required for her work.
Construct a simple pinhole projector to safely observe the sun. Use materials like a cardboard box, aluminum foil, and a piece of white paper. This activity will teach you about the principles of light projection and allow you to safely observe solar phenomena just like Koyama did.
Research how solar flares are formed and their impact on Earth. Create a presentation or a poster to share your findings with the class. This will help you understand the significance of Koyama’s work in tracking solar activity and predicting solar flares.
Using online tools or software, simulate the 11-year sunspot cycle. Track the movement and number of sunspots over time and create a graph to visualize the cycle. This activity will help you understand the cyclical nature of solar activity and the importance of long-term observation.
Imagine you are Hisako Koyama during one of her observation sessions. Write a diary entry describing your experience, the challenges you face, and the excitement of discovering new sunspots. This creative writing activity will help you empathize with Koyama and understand the personal dedication behind her scientific contributions.
Hisako – a Japanese given name for females – Hisako is a popular name for girls in Japan.
Koyama – a Japanese surname – Mr. Koyama is a renowned artist from Japan.
Woman – an adult female human – The woman walking down the street was carrying a large bag.
Records – written or recorded information – The historical records show that the building was constructed in 1892.
Solar Activity – the phenomena occurring on the Sun’s surface – Scientists closely monitor solar activity to study its effects on Earth’s environment.
Important – of great significance or value – It is important to take care of our environment for future generations.
Astronomical Phenomena – natural events occurring in outer space – The Northern Lights are an incredible astronomical phenomena.
Sun’s Light – the radiant energy emitted by the Sun – The sun’s light provides warmth and sustains life on Earth.
Sun’s Surface – the outer layer of the Sun – Powerful solar flares can occur on the sun’s surface.
Sunspots – dark spots that appear on the Sun’s surface – Astronomers use telescopes to observe and study sunspots.
