Mauna Kea Observatories
Published on Aug 5, 2007 at 1:33 pm.
7 Comments.
Filed under astronomy, observatories, telescopes, wonders.
Situated atop Mauna Kea in Hawaii are 13 telescopes funded by 11 countries: 9 optical telescopes, 2 submillimeter telescopes, 1 submillimeter array, and 1 radio telescope. All together, this comprises the Mauna Kea Observatories (or the Mauna Kea Observatory as the whole installation is sometimes called).
The optical telescopes range in size from a 0.6 meter diameter telescope used by the University of Hawaii up to twin 10 meter telescopes: Keck I and Keck II. Several of the telescopes, such as the 3.8 meter United Kingdom Infrared Telescope, the 8.3 meter Subaru Telescope, and the submillimeter 15 meter James Clerk Maxwell Telescope are operated by foreign science organizations. Many of the telescopes, such as the 3.6 meter Canada-France-Hawaii Telescope and the 8.1 meter Gemini North Telescope are multinational. Most of the telescopes are also multi-institutional. Many are among the largest telescopes in the world, and many are fitted with cutting edge technology.
So, why are there so many world class telescopes built on Mauna Kea by nations all over the world? Well, quite simply, Mauna Kea is a fantastic place to build an observatory. Located at less than 20° N latitude, Mauna Kea is farther south than most other northern hemisphere observatories, permitting the telescopes there to observe more of the sky. But, more importantly is the geography of the site. Located in the middle of the Pacific Ocean, there is little landmass around to mess with atmospheric circulation, so sky conditions are reliable and predictable, and very stable, permitting clear viewing with minimal distortion. Even better, at an altitude of about 13,800 feet (4200 meters), 2.6 miles above the ocean, the summit of Mauna Kea is higher than about 40% of the Earth’s atmosphere. The less air that you look through, the less that you have to contend with distortion and attenuation of light from celestial objects. Even better, a tropical inversion layer keeps the moisture laden air near the surface from rising to the level of the summit except on rare occasions. This means that the top of the mountain is nearly always clear and dry, even if it is raining down near the foot of the mountain (which it often does). A further benefit to this atmospheric condition is that pollutants from the urban areas in Hawaii also seldom rise to the top of the mountain. Most people, and most cities, are within a short distance to the coast, so there are also few city lights to bother the observing at the top of the mountain.
Mauna Kea (Hawaiian for White Mountain) is a dormant volcano. It is classified as a post shield volcano. Perhaps 200,000 years ago, its eruptions changed from the lava flows characteristic of nearby Mauna Loa (a classic shield volcano) to a somewhat more explosive type of eruption, filling the summit caldera and building numerous cinder cones atop the mountain. As a dormant volcano, there are long periods of time between eruptions on Mauna Kea. The last eruption was about 4000 years ago. Though geologists feel that it is likely that Mauna Kea could erupt again, but such an eruption is not likely any time soon. Ironically, the astronomical work atop Mauna Kea requires such precision that the telescopes can act as super-sensitive monitors for any seismic activity below the mountain that might precede any eruption.
The extreme altitude of the observatory makes visiting it difficult. Astronomers working at the observatory often suffer hypoxia if they are not used to working at such altitudes. A bit over halfway up the mountain is a visitor’s facility, the Onizuka Center for International Astronomy (named for Ellison Onizuka, who was killed in the Space Shuttle Challenger accident). Astronomers stop at the Onizuka Center to acclimatize to the altitude before proceeding on to the summit. The Onizuka Center also has a visitor’s center, with public displays, for anyone wishing to learn more about the observatory. There are even guided tours of the summit. Visitors, though, are encouraged to make sure that they can handle the altitude before going to the top of the mountain to avoid serious, or even life threatening, health issues.
The Keck Observatory is the perhaps the showpiece of the Mauna Kea Observatory. There are two identical Keck telescopes, Keck I (which became operational in 1993) and Keck II (which became operational in 1996). The Keck telescopes were among the first telescopes to use an array of mirrors to form a reflecting surface rather than a single mirror. Each mirror of the Keck telescopes is composed of 36 hexagonal segments. Computers monitor the position of the segments and use actuators to adjust the position of each segment 120 times per minute to compensate for distortions in the reflecting surface due to temperature or gravity. This procedure, known as active optics, gives the reflecting surface a proper shape to within 4 nanometers. The Keck telescopes are also equipped with adaptive optics to provide nearly unparalleled images. With adaptive optics, the light from the primary reflector is focussed onto a small 6 inch thin mirror whose shape can be adjusted 670 times per second to compensate for atmospheric distortion. This increases the telescopes operational resolution by a factor of ten or more. The two Keck telescopes can also be used together as an optical interferometer to yield a resolution (in one direction) equivalent to a single reflector 85 meters across.
But, Keck is not the only showpiece at Mauna Kea. The Gemini North Telescope is part of a pair of identical telescopes (the other is located in Chile near Cerro Tololo Inter-American Observatory) that can observe the entire sky. The Gemini telescopes are operated by a seven nation consortium, and at 8.1 meters in diameter are the seventh largest telescopes on Earth (counting the Keck telescopes as one, and likewise counting ESO’s Very Large Telescope as one). Even larger is the Subaru Telescope, operated by the National Astronomical Observatory of Japan. Subaru employs state of the art technology and is in its own right a world class observatory.
Mauna Kea Observatory is also home to three sub-millimeter instruments. Sub-millimeter wavelengths are sort of between infrared light and radio waves. Infrared astronomers like to claim sub-millimeter wavelengths as very far infrared, and radio astronomers often claim sub-millimeter wavelengths as ultra short microwaves. Either way, it doesn’t make much difference what you call it! The telescopes look a lot like satellite dishes to me, so I generally think of sub-millimeter astronomy as microwave astronomy. Sub-millimeter wavelengths have trouble making it past water vapor in Earth’s atmosphere, so sub-millimeter telescopes need to be atop tall mountains in order to be above most of the water vapor. Mauna Kea is an idea site for sub-millimeter telescopes, since its altitude is above 40% of Earth’s atmosphere, but above 90% of the water vapor in the atmosphere. Two of Mauna Kea’s sub-millimeter telescopes are single reflector instruments, and one is an array (sort of like a miniature version of the VLA).
So, if you ever get to the Big Island of Hawaii, it would be worth your while to at least visit he Onizuka Center if not the summit of Mauna Kea to see this world class observatory.
-Astroprof
Observatory Images Credit: Wikimedia
Mauna Kea Image Credit: USGS
Mirror Comparison Diagram: University of Hawaii
A Ler…-- Rastos de Luz on August 6, 2007 at 12:38 pm: 1
[…] Mauna Kea Observatories, The European Southern Observatory e Mt Palomar Observatory no Astroprof’s Page Phoenix wrapup no The Planetary Society Blog […]
Kelly on August 8, 2007 at 5:44 pm: 2
Astroprof, I know this has nothing to do with your post, but I know you are the right one to ask about this email that’s circulating. Can you tell us anything about it? Your past posts about such emails have been very enlightening.
______________________________
*27th Aug the Whole World is waiting for………….*
Planet Mars will be the brightest in the night sky starting August.
It will look as large as the full moon to the naked eye. This will culminate on Aug. 27 when Mars comes within 34.65M miles of earth. Be sure to watch the sky on Aug. 27 12:30 am midnight. It will look like the earth has 2 moons. The next time Mars may come this much closer in 2287.
Share this with your friends as NO ONE ALIVE TODAY will ever see it again.
Astroprof on August 9, 2007 at 12:15 am: 3
This is the subject of my next entry. It is an urban myth that has been circulating for the last four years.
Astroprof’s Page » Hotel Mauna Kea on January 4, 2008 at 2:11 pm: 4
[…] Some of you may remember my posting about the Mauna Kea Observatories this past summer. If not, you can read it here. […]
Telescopes on March 18, 2008 at 5:55 pm: 5
I’ve always wanted to visit one of those huge observatorys.
Telescopes on March 18, 2008 at 5:56 pm: 6
I’ve always wanted to visit one of those huge observatorys.
Westerberg on May 13, 2009 at 12:30 am: 7
If I understand correctly… this tour picks you up at 4 to 5pm and you stay all night on the summit… then return around 9 or 10am the next morning? That would be VERY cool! Would you have an opportunity to set up your own photography equipment during this tour to get star trails shots?