DATE2025.02.12 #News

Big Data Science in the Beautiful Night Sky of Kiso

～An observatory where research, education, and society meet〜

At first glance, the star-filled universe seems eternal and unchanging, but closer inspection reveals that it is actually evolving from moment to moment, even on the scale of seconds. Did you know that Kiso Observatory, operated by the University of Tokyo in Nagano Prefecture, monitors this ever-changing universe every night using state-of-the-art equipment? The ceremony celebrating the 50th anniversary of Kiso Observatory was held on December 8, 2024, at the Cultural Hall of Kiso Cultural Park in Kiso County, Nagano Prefecture, with many distinguished guests in attendance. The symposium, which was open to the public, began with a lecture on the Kiso Schmidt Telescope by Mamoru Doi, Director of the National Astronomical Observatory of Japan (and former Director of the Institute of Astronomy), followed by a panel discussion titled "Infinite Possibilities in Nagano Prefecture’s Night Sky." The discussion actively explored regional revitalization initiatives leveraging the area’s star-filled skies. During the ceremony, Dean Okoshi of the Graduate School of Science presented a letter of appreciation to Governor Abe of Nagano Prefecture and others who have significantly contributed to the observatory. The event was held in a warm and celebratory atmosphere from start to finish. Kiso Observatory was established in 1974 and has since fostered many astronomers and made significant astronomical contributions. As the only domestic observatory operated by the University of Tokyo, it has been dedicated to research and education, and in recent years has also focused on social engagement and regional collaboration. Now, half a century since its founding, its mission has become more vital than ever.

The 50th Anniversary Ceremony of Kiso Observatory

The centerpiece of the observatory, a specialized Schmidt-type telescope with a 1.05-meter aperture, can capture a wide area of the sky in a single image, making it ideal for discovering previously unknown celestial objects. As a telescope with crucial functions for Japanese astronomy—which was still in its early stages following World War II—it was constructed as one of the main facilities of the University of Tokyo's Tokyo Astronomical Observatory at the time. Since Japan had little experience in constructing large domestic telescopes, the project required extensive trial and error by numerous astronomers and engineers. The construction of this telescope was undertaken by Nippon Kogaku (now known as Nikon), making it the largest "camera" the company had ever built. Although this type of telescope is widely used in modern astronomical projects, large Schmidt telescopes exceeding 1 meter in aperture remain rare worldwide for general-purpose astronomical research. The fact that one of them is located in Japan not only holds historical and cultural significance but also underscores Japan's continued advantage in cutting-edge astronomical research today.

The Kiso Schmidt Telescope under construction

The observatory was built in a mountainous area with no existing infrastructure, requiring the construction of roads and the installation of electricity and water lines from scratch. Additionally, because the forestry industry was thriving at the time, the value of the surrounding forests was high, making it difficult to secure and maintain a large site. Even cutting down a single tree that obstructed operations required extensive negotiations with the local community. During Japan’s bubble economy, when skiing was booming, ski resorts were brightly lit even at night, necessitating discussions with the local community to minimize light pollution. Over the past 50 years, observation technology has evolved from analog photographic plates to digital CCD cameras, and more recently to advanced CMOS cameras. Consequently, the quality and quantity of astronomical data have increased dramatically. The observatory’s ability to adapt flexibly to these technological advancements and establish itself as a center for the transmission of astronomical observation techniques and culture is largely due to the visionary aspirations of its founders, the dedication of successive generations of observatory staff who upheld these ideals, and the steadfast support of the local Kiso community and the people of Nagano Prefecture.

Telescope tour at the Star Classroom

The observatory has been advancing research and education as one of the central hubs of Japanese observational astronomy. It holds great significance for the Japanese astronomical community, as it has served as a training ground for students from the Department of Astronomy at the University of Tokyo’s School of Science, as well as for university students from across Japan. As a local facility that bridges the University of Tokyo’s School of Science with the surrounding community, the observatory actively engages in numerous social outreach and community collaboration projects throughout the year. These include telescope tours, astronomy courses, public lectures, and partnerships with local events. In particular, its accommodation facilities, which can host up to 40 people, are used to conduct outreach camps for high school students. The "Galaxy School," a four-day, three-night program for selected high school students from across Japan, has been a popular hands-on astronomy training program since its inception in 1998. It is now recognized as a pioneering initiative that has inspired similar programs nationwide. Meanwhile, the "Star Classroom" offers high school students from Nagano Prefecture a two-day, one-night immersive experience at the observatory, where they attempt to determine the age of the universe on their own. This program has come to symbolize the University of Tokyo’s commitment to giving back to the local community in Nagano Prefecture. Many graduates of these programs have pursued careers in science and engineering, with some becoming professional researchers in astronomy and physics. Situated at an altitude of 1,120 meters, the observatory is surrounded by towering mountains—such as Mount Ontake and the Central Alps—which shield it from urban light pollution. It is renowned as one of Japan’s premier observatories, offering an exceptionally clear and breathtaking starry sky. Once you witness this celestial spectacle, it is impossible not to be captivated by astronomy—and, more broadly, by the wonders of natural science. For science majors, the observatory embodies the profound value of having a local facility where they can connect directly with nature.

Tomo-e Gozen mounted on the Kiso Schmidt Telescope

In 2019, Kiso Observatory installed its latest instrument, Tomo-e Gozen, which enables us to capture high-speed movies of celestial objects within an ultra-wide field of view, spanning 9 degrees in diameter. With this system, the entire sky—containing more than 500 million stars—can be observed in about two hours, ensuring that even the slightest variations are recorded in detail. Observations using Tomo-e Gozen have revealed that even ordinary stars, which appear eternal and unchanging, frequently undergo rapid changes lasting less than a second, including flares, explosions, and other transient phenomena. As a result, Kiso Observatory is emerging as a key center for "time-domain astronomy," receiving observation requests from various astronomical projects worldwide for objects likely to exhibit such variations. Tomo-e Gozen is also the world's most advanced system for detecting near-Earth asteroids that may collide with Earth. Because it continuously records moving images, it can effectively track fast-moving objects across its field of view. Jin Beniyama, who earned his doctorate in 2024 based on research using Tomo-e Gozen and is currently continuing his studies in France, remarks, "I am frequently asked about Tomo-e Gozen’s achievements by researchers studying asteroids and solar system bodies around the world. I can truly feel the global attention it has garnered."

As Kiso Observatory celebrates its 50th anniversary, various new developments are anticipated in the coming years. Director Naoto Kobayashi (Associate Professor) states, "Kiso Observatory excels particularly in its ability to track fast-moving objects. We believe it is important to expand our targets beyond asteroids to include artificial objects such as space debris and to establish the observatory as a unique provider of a database of fast-moving objects, which would also be valuable for space operations." The observatory is also actively searching for new targets, including supernovae, gravitational waves, and other astronomical phenomena. A follow-up system for rare objects—such as gravitational wave sources and unknown radio signals, whose mere discovery would be groundbreaking—has been developed as one of the observatory's key projects and is currently in place, awaiting the appearance of these elusive objects. The universe continuously presents new discoveries, and as Nobel Prize-winning physicist Dr. Masatoshi Koshiba once said, "Opportunities come only to those who prepare for them carefully." Assistant Professor Yu Niino, who oversees the follow-up programs, echoes this sentiment, stating, "We strive to be a well-prepared observatory that patiently awaits opportunities and is the first to seize them."

Another major transformation over the past 50 years has been the shift to big data-driven observational astronomy. Kiso Observatory not only surveys a wide area of the sky but also operates with high-speed time resolution at the scale of seconds, making it one of the most prolific observatories in generating multi-dimensional data across space and time. The observatory has evolved into a "Big Data Observatory," where acquired data is transmitted, analyzed, and made publicly available on the same day. This is achieved by linking the observatory—located in the mountains—to the mdx data platform at the University of Tokyo's Kashiwa Campus, which serves as the central data server, via the SINET6 academic information network. Vice Director (Associate Professor) Shigeyuki Sako, who leads the development and operation of Tomo-e Gozen and has been a key advocate of this Big Data initiative, proudly states, "This advancement will enable Kiso Observatory to fully establish itself as a leading center for time-domain astronomy in Japan."

Imaginary image of a fast-spinning asteroid passing near the Earth ( from the press release on July 13, 2022 )

The significance of astronomical research and education at the observatory will remain a fundamental pillar, but as a local facility directly connected to society, the observatory should also be accessible and familiar to the general public—in other words, "an observatory cherished by the local community and society." This is what defines the observatory as a long-term infrastructure, distinct from short-lived projects that are built and later dismantled, and it will provide even greater academic contributions over the medium to long term. "We believe that all three elements are indispensable: cutting-edge research; higher education that supports and enables such research; and social engagement and regional collaboration that reinforce both research and education. By explicitly expanding our focus to include social contribution, we aim to create a new type of university facility—one that is both open and stable. I look forward to seeing what kind of synergies will emerge when these three realms interact," Director Kobayashi remarked. The light from the stars shines equally upon everyone, and perhaps astronomy is the field that embodies this universality most naturally.

(Responsibility: Associate Professor, Director of Kiso Observatory Naoto KOBAYASHI)

Link

Kiso Observatory, The University of Tokyo
Institute of Astronomy, Graduate School of Science, The University of Tokyo
The University of Tokyo, School of Science Fund (Departmental Fund) ^{in Japan}