The Explorers of Mauna Kea
A remarkable mountain in Hawaii

November, 2001 Observer's Notebook

by John Rummel

Large astronomical observatories are stereotypical "big science." Other large budget science projects can be difficult to comprehend for the average citizen. Try to visualize the human genome or imagine using a huge particle accelerator. Not many people know exactly what they are or how they're likely to benefit. Show a picture of a big telescope though, and everybody knows what it's for.

Of the 30 largest telescopes in the world ("large" here being defined as 3 meters or bigger), seven of them are located on a single mountain top in Hawaii. No other location is even close unless you count the entire coastal mountain range in Chili, which boasts 5 out of the top 30, but these are at widely separated locations, not all clustered on one summit like Hawaii's Mauna Kea.

One of the W. M. Keck Observatory telescopes (foreground) with the NASA Infrared Telescope Facility and the Canada-France-Hawaii telescopes in the background.
UH 2.2 meter telescope (left) and Gemini North Telescope.

What's so special about this mountain, actually a dormant volcano, in Hawaii? The answer goes to the heart of observational astronomy. To observe the sky, you need three things: 1) large telescopes, 2) clear skies, and 3) altitude. Numbers one and two are essential. A large telescope built in a location where skies are cloudy most of the time will be of little use. Or a tiny telescope under the clearest skies in the world will be of negligible value to scientists. Number three is optional, but very useful for professional astronomers. The higher your telescope is above sea level, the less atmosphere between you and the objects you're looking at. This is crucial in some wavelengths of light due to the amount of water vapor in our air near sea level.

Mountain tops are also usually located far away from large cities, making the problem of light pollution less significant.

Mauna Kea's unique qualities as a platform for telescopes was first noted in the early 1960's by University of Arizona astronomer Gerard Kuiper. Kuiper knew the mountains in Arizona were excellent observing platforms, but wanted something even higher and more remote for a new observatory. He first visited Mt. Haleakala on the island of Maui. Haleakala was the site of a newly dedicated solar observatory for the University of Hawaii, and Kuiper saw that, at 10,000 feet elevation, it was an excellent site, but noticed that the clouds and moisture tended to creep in and fog over the summit many nights, ruining the viewing. Looking around, he noted that the peak of Mauna Kea on the neighboring island of Hawaii was in the clear. Kuiper inquired about the larger mountain on Hawaii and was soon conducting tests there as well.

Mauna Kea was not considered seriously as an observing site before because of its remoteness and the fact that there was no paved road to the summit. This all changed over the next few years as Kuiper's proposal for an observatory there was accepted and funded by NASA. The superb qualities of Mauna Kea soon became legendary within the astronomy community and other scientists and organizations began to apply for building permits from the state of Hawaii too.

At nearly 14,000 feet above sea level, Mauna Kea is the largest mountain in the Pacific basin, and if measured from the sea floor, it is the tallest mountain on Earth (nearly 32,000 feet high). Its ideal conditions for astronomy are attested to by the fact that it is now home to 13 observatory facilities. This incredible growth has been tempered by the fact that the scientists have to be sensitive to the cultural and ethnic heritage of the mountain, and its importance to native Hawaiians.

Visit the official Mauna Kea Observatory site here.

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