Akashi City Astronomical Science Museum

Akashi Municipal Planetarium: Where Time and the Cosmos Converge

Standing proudly on the Japan Standard Time Meridian at exactly 135 degrees east longitude, the Akashi Municipal Planetarium (明石市立天文科学館) is far more than a science museum — it is a living monument to humanity's relationship with time and the universe. Located atop a gentle hill in Akashi City, Hyogo Prefecture, this iconic building with its soaring clock tower has served as the symbolic heart of "The Town of Time" since its opening on June 10, 1960 — a date chosen to coincide with Japan's annual "Time Day" (時の記念日).

As the oldest astronomical science museum still in operation in Japan and a nationally Registered Tangible Cultural Property, the Akashi Municipal Planetarium invites visitors from around the world to explore the mysteries of time, the stars, and the meridian line that defines Japan's standard time.

Historical Background: A Century of Meridian Heritage

The story of Akashi's connection to time begins in 1884, when the International Meridian Conference in Washington, D.C. established the Greenwich meridian as the global prime meridian. Two years later, in 1886, Japan adopted the 135th meridian east as its standard time meridian, placing Akashi squarely at the center of Japan's timekeeping identity.

In 1910, local school principals in Akashi recognized the significance of the meridian passing through their city and erected the first meridian marker. This visionary act launched Akashi's enduring identity as "The Town of Time." In 1928, the city conducted precise astronomical observations to determine the exact position of the 135th meridian, and in 1930, the famous dragonfly-shaped meridian marker was installed on Hitomaru Hill.

After World War II, renewed interest in commemorating the meridian led to the construction of a dedicated science museum. On June 10, 1960 — Time Day — the Akashi Municipal Planetarium opened its doors to the public. The museum was designed as a composite structure featuring a four-story exhibition hall with a circular planetarium dome measuring 23 meters in diameter, and a 54-meter-tall clock tower built directly on the meridian line, serving both as an observation platform and a monumental marker of the Japan Standard Time Meridian.

Cultural Property Designation: Why This Building Matters

On September 10, 2010, marking its 50th anniversary, the Akashi Municipal Planetarium was registered as a national Registered Tangible Cultural Property (国登録有形文化財) by the Japanese government. The designation recognizes several exceptional qualities of this mid-20th-century modernist structure.

The building is a reinforced concrete structure comprising a four-story exhibition wing — including a circular planetarium hall 23 meters in diameter — and a high tower reaching 54 meters. The tower features a distinctive double-shell construction, with an inner tower and an outer tower designed to protect the optical telescope at the summit from wind-induced vibrations. The upper floors house an observation deck and an astronomical observation room, while the tower's large clock displays Japan Standard Time to the surrounding city.

The structure is valued not only as a fine example of postwar public architecture but also for its unique role as a functional meridian marker and civic landmark. Its selection as one of Japan's "100 Best Public Buildings" by the Ministry of Construction in 1998 further underscores its architectural and cultural significance.

Highlights and Attractions

Japan's Longest-Operating Planetarium

The crown jewel of the museum is its planetarium, equipped with a Carl Zeiss Jena UPP23/3 projector manufactured in the former East Germany. Installed at the museum's opening in 1960, this remarkable instrument has been in continuous operation for over six decades, achieving the longest operational record of any planetarium in Japan and ranking among the top five worldwide. Featuring several hundred lenses, nearly 200 gears, and 90 lamps, the projector can display approximately 9,000 fixed stars along with the sun, moon, five planets, the Milky Way, comets, and variable stars. Each show is narrated live by museum curators, continuing a tradition of personal, expert-led commentary that has been maintained since the museum's founding.

The Clock Tower and Observation Decks

The museum's 54-meter clock tower is crowned by a large clock face approximately 6.2 meters in diameter, inscribed with the letters "JSTM" — Japan Standard Time Meridian. The current clock is the third generation, installed in 1997 after the second-generation clock stopped at 5:46 a.m. during the Great Hanshin Earthquake of 1995. The 13th and 14th floors serve as observation decks offering 360-degree panoramic views of the Akashi Strait, Awaji Island, and the Akashi Kaikyo Bridge.

Exhibition Galleries

The museum's exhibition spaces are organized into four thematic zones: "Meridian Town Akashi," the "Astronomy Gallery," the "Observation Archives," and the "Time Gallery." Visitors can explore displays on the history of timekeeping, models of the solar system and galaxy, meteorite specimens, spacecraft replicas, and interactive exhibits about black holes and the structure of the universe. A water clock (漏刻) — inspired by the ancient timekeeping device used by Emperor Tenji in 671 AD — is installed along the meridian line at the museum entrance.

Astronomical Observation Room

On the 16th floor, the museum's astronomical observation room houses a 40-centimeter aperture telescope. Public stargazing events are held approximately once a month, giving visitors the opportunity to observe celestial bodies through professional-grade equipment.

Surviving the Great Hanshin Earthquake

On January 17, 1995, the Great Hanshin-Awaji Earthquake struck the Kobe-Akashi region with devastating force. The museum suffered severe damage — the inner tower fractured internally, the telescope toppled, and the clock tower stopped at the moment of the earthquake, 5:46 a.m. However, the planetarium projector survived entirely unscathed, becoming a powerful symbol of resilience and recovery.

Three years of extensive reconstruction followed, including the complete rebuilding of the inner tower structure. The museum reopened on March 15, 1998, and the undamaged planetarium projector resumed its faithful service — a source of deep emotional significance for the people of Akashi.

Visitor Information

The Akashi Municipal Planetarium is open from 9:30 a.m. to 5:00 p.m. (last admission at 4:30 p.m.). General admission is 700 yen for adults, which includes access to planetarium shows. Admission is free for high school students and younger. The museum is closed on Mondays and the second Tuesday of each month (if these fall on a national holiday, the museum opens and closes the following day instead), as well as during the year-end period. Discounts are available with JAF membership cards and certain other programs.

Please note that the museum is currently undergoing renovation work and is fully closed from October 1, 2025 through summer 2026 (scheduled). Visitors are advised to check the official website for the latest reopening information before planning a visit.

The museum is conveniently located about a 3-minute walk from Hitomaru-mae Station on the Sanyo Electric Railway, or approximately 15 minutes on foot from JR Akashi Station. A parking lot with approximately 90 spaces is available on the east side of the building (200 yen for 2 hours).

Surrounding Attractions

The area around the museum offers several worthwhile destinations. Kakimoto Shrine (柿本神社), dedicated to the celebrated poet Kakinomoto no Hitomaro, sits adjacent to the museum on Hitomaru Hill. Nearby Gesshoji Temple (月照寺), founded by the great Buddhist monk Kukai (Kobo Daishi) in 811 AD, provides a tranquil atmosphere steeped in history.

A short walk to the west brings visitors to Akashi Park and the ruins of Akashi Castle, where two original corner turrets from the Edo period still stand. The lively Uontana Shopping Street (魚の棚商店街) near JR Akashi Station is a must-visit for food lovers, offering fresh seafood and the local specialty akashiyaki — delicate egg-based octopus dumplings served in warm dashi broth.

For visitors with more time, the Akashi Kaikyo Bridge — one of the world's longest suspension bridges — connects Akashi to Awaji Island and can be admired from the museum's observation deck or visited up close at the nearby Maiko Marine Promenade.