Astronomical Heritage Finder


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Short Description (ICOMOS-IAU Case Study format):
Mauna Kea Observatory, Hawaii, USA


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Latitude 19° 49′ 30″ N, longitude 155° 28′ 25″ W. Elevation 4100m above mean sea level.


General description 
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Mauna Kea (‘White Mountain’) is a dormant volcano on the island of Hawaii, the largest and southernmost of the Hawaiian Islands. The highest point in the Pacific Basin, and the highest island-mountain in the world, Mauna Kea rises 9750 m from the ocean floor to an altitude of 4205 m above sea level, which places its summit above 40 percent of the Earth’s atmosphere. The broad volcanic landscape of the summit area is made up of cinder cones on a lava plateau.

Mauna Kea is unique as an astronomical observing site. The atmosphere above the mountain is extremely dry—which is important in measuring infrared and sub-millimetre radiation from celestial sources—and cloud-free, so that the proportion of clear nights is among the highest in the world. The smooth shape of the isolated mountain, along with its high altitude, produces astronomical image quality that is among the best of any location on Earth. The atmospheric pressure at the summit is approximately 600 mb.


Brief inventory 
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Telescopes: Keck I and II, Subaru, Gemini North, IRTF, UKIRT, CFHT, JCMT, CSO, SMA, UH 2.2m and 0.9m, VLBA.

Fig. 1: View of Mauna Kea observatory showing the Subaru, Keck I and II, and IRTF telescopes.
Photograph © Sasquatch at Wikimedia Commons, Creative Commons Licence


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The first large telescope on Mauna Kea, the 2.2m, demonstrated the remarkably stable and dry atmosphere above the observatory, and led to the development of a series of larger telescopes, many of which are owned and operated by international countries or partnerships. Mauna Kea was recently selected as the site for the Thirty Meter Telescope.


Cultural and symbolic dimension 
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The Mauna Kea Observatory forms part of a single set of sites in the world with exceptional conditions for observing the Universe. These sites, including their natural and cultural components, are exceptional ‘windows of science and knowledge’.



Present use 
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The observatory is the site of the telescopes listed above.

The Mauna Kea Visitor Center is open 365 days per year, and offers summit tours on weekends and evening stargazing. The annual visitor count exceeds 250,000. Astronomers and staff from the Mauna Kea Observatories are also engaged in extensive outreach activities across the island of Hawaii, and elsewhere in the Hawaiian Islands.


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The zone around the observatory is called the “Mauna Kea Science Reserve” and has strict controls on usage. A subset of this reserve is designated for astronomical usage. A pie-shaped sector of the zone around the observatory is preserved as the “Mauna Kea Ice Age Reserve”. A lighting ordinance for the island of Hawaii has been established to limit artificial light and its damaging effects on the observatories.

A large area around the science reserve is preservation land owned by the state of Hawaii. Few people live within 25 km of the summit.


State of conservation 
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The observatory has been in operation for 40 years. The buildings and telescopes are well maintained, consistent with the operation of a major research facility.

The lighting ordinance has been in place for 20 years, and has provided good protection for the night sky. However, there are many lights on the island that do not conform to the ordinance, either because they were installed prior to it, or have been installed in violation. Better enforcement is expected in the future. The present level of light pollution does not compromise research.

An ongoing eruption of nearby Kilauea volcano is producing copious amount of volcanic gases and haze. These gases are nearly always trapped at lower altitudes by a temperature inversion, and do not affect the astronomy.


Context and environment 
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The summit region is sacred to the native Hawaiians. The summit area is a spectacular natural landscape composed of multiple cinder cones, a high altitude lake, and glacial moraine field.


Archaeological / historical / heritage research 
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An ancient adze quarry is located to the south of a summit, with very hard rocks formed during the last ice age from lava being cooled by a glacier; the hard rocks were used as tools by pre-European-contact Hawaiians. Numerous archaeological monuments are located around the summit region.


Main threats or potential threats 
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The main threat is light pollution from the nearby urban areas. Population growth is occurring mostly on the western (dry/clear) side of the island, leading to increasing artificial light.


Management, interpretation and outreach 
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The Mauna Kea Science Reserve and Ice Age Reserve are owned by the State of Hawaii. A large area around these reserves is also owned by the State of Hawaii.

The summit area is managed by the Office of Mauna Kea Management of the University of Hawaii. Rangers patrol the summit area for conservation purposes and to assist visitors with problems. The larger conservation area surrounding the summit is managed by the Department of Land and Natural Resources of the State of Hawaii.

Each of the telescopes has a sublease from the University of Hawaii. The University of Hawaii has leased the Mauna Kea Science Reserve from the State of Hawaii. The lease expires in 2031.


Entity Data

Thematic essay: ‘Windows to the universe’: Starlight, dark-sky areas and observatory sites

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