If you’ve ever looked at a stunning photo of deep space or read about a new planet, there’s a good chance the data came from a mountain in Hawaii. You might wonder, how many telescopes on Mauna Kea are making these discoveries possible? The answer is more complex than a single number, as it involves both active facilities and those that have been decommissioned. This guide will give you a clear count and explain why this mountain is so special to astronomers worldwide.
Mauna Kea is a dormant volcano on the Big Island of Hawaii. Its peak rises an incredible 13,803 feet above sea level. But that’s just the start. Measured from its base on the ocean floor, it’s over 33,000 feet tall, making it the tallest mountain on Earth. This height is key. It places the telescopes above 40% of Earth’s atmosphere and 90% of its water vapor. The air is dry, calm, and exceptionally clear. For astronomers, it’s the best site for ground-based observation on the planet. The view of the night sky is simply unrivalled.
How Many Telescopes On Mauna Kea
As of 2024, there are 12 active operational telescopes on the summit of Mauna Kea. However, the full historical count is higher. In total, 13 major telescope facilities have been constructed there. One of these, the Caltech Submillimeter Observatory (CSO), has concluded operations and is in the process of being decommissioned and removed. So, when people ask how many are there, they usually mean the active ones: twelve.
It’s important to think of these as observatories, not just single telescopes. Each facility is a complex structure housing advanced instruments. They are managed by consortia from different countries and institutions. This global collaboration highlights Mauna Kea’s international importance in science.
The Complete List of Active Mauna Kea Telescopes
Here is a rundown of all twelve currently functioning telescopes, listed roughly in order of their size or aperture.
- Keck Observatory (Twin Telescopes): The two Keck telescopes are the largest optical/infrared telescopes on the summit. Each has a primary mirror 10 meters (33 feet) in diameter. They can work together as an interferometer, achieving incredible resolution.
- Gemini North Telescope: Part of the international Gemini Observatory, this telescope has an 8.1-meter mirror. Its twin, Gemini South, is in Chile, allowing astronomers to see the entire sky.
- Subaru Telescope: Operated by Japan, Subaru is a massive 8.2-meter optical-infrared telescope. It’s famous for its wide-field imaging, capable of capturing huge areas of the sky in great detail.
- NASA Infrared Telescope Facility (IRTF): A 3.2-meter telescope dedicated entirely to infrared astronomy. It is a vital tool for studying our solar system, including planets and asteroids.
- Canada-France-Hawaii Telescope (CFHT): This 3.6-meter telescope is a pioneer on the mountain, beginning operations in 1979. It continues to do cutting-edge wide-field imaging and spectroscopy.
- James Clerk Maxwell Telescope (JCMT): The largest single-dish telescope in the world designed specifically to observe submillimeter wavelengths. It studies cold gas and dust in the universe.
- Submillimeter Array (SMA): An interferometer consisting of eight movable antennas, each 6 meters in diameter. It works in concert with JCMT to provide detailed submillimeter images.
- University of Hawaii 2.2-meter Telescope: One of the older telescopes on the summit, this workhorse instrument has been used for a vast array of astronomical research since 1970.
- W. M. Keck Observatory Outrigger Telescopes (Dormant): These were planned as smaller telescopes to complement the Keck interferometer, but the project was canceled. The domes exist but are not used for active observation.
- Very Long Baseline Array (VLBA) Antenna: This is a 25-meter radio dish that is part of a continent-wide network of identical antennas. Together, they create a radio telescope thousands of miles in size.
- One Earth Messenger Telescope (UCLA): A smaller, modern telescope used for laser guide star experiments and supporting adaptive optics systems.
The History and Context of Telescope Construction
The first telescope to arrive on Mauna Kea was a modest 0.6-meter instrument installed by the University of Hawaii in 1968. The exceptional viewing conditions were immediately obvious. This led to a wave of construction through the 1970s, 80s, and 90s. Each new telescope was more advanced and larger than the last, culminating with the twin Keck telescopes in the 1990s and the Subaru telescope in 1999.
This growth, however, was not without controversy. Mauna Kea, or Maunakea, is considered the most sacred mountain in Native Hawaiian culture. It is viewed as the realm of the gods, a place of worship, and a connection to ancestors. The construction of numerous large, industrial facilities on the summit has been a source of deep conflict for decades.
Understanding the Decommissioning Process
In response to these concerns, the Hawaiian community and the state government established new management frameworks. A key policy now is a “decommissioning plan.” For every new telescope proposal, an older one must be removed. The goal is to reduce the total footprint of astronomy on the mountain.
- The Caltech Submillimeter Observatory (CSO) is the first major telescope to undergo full decommissioning. Its dome has been removed and the site is being restored.
- The Very Long Baseline Array (VLBA) antenna is also scheduled for removal in the coming years.
- The future Thirty Meter Telescope (TMT) project, if built, would require several existing smaller telescopes to be decommissioned.
This means the number of active telescopes will likely fluctuate in the coming decade, but the trend is toward fewer, more powerful instruments.
What Makes Mauna Kea So Special for Astronomy?
Several unique factors combine to make Mauna Kea the premier observing site on Earth. It’s not just one thing, but a perfect storm of ideal conditions.
- Altitude: At nearly 14,000 feet, the summit is above much of the Earth’s dense, turbulent atmosphere. This reduces “twinkling” and provides sharper images.
- Dry Air: High altitude means very low humidity. Water vapor absorbs infrared and submillimeter light, so a dry site is crucial for those types of astronomy.
- Dark Skies: The remote location in the middle of the Pacific Ocean means minimal light pollution. The night sky is among the darkest on Earth.
- Stable Air: The smooth ocean air flows steadily up the mountain, creating stable atmospheric conditions above the summit, which is essential for clear viewing.
- Latitude: Hawaii’s location at 20 degrees north latitude allows astronomers to see almost all of the northern sky and much of the southern sky.
The Science Coming From the Summit
The telescopes on Mauna Kea have contributed to nearly every major astronomical discovery in the last 50 years. They are not just taking pretty pictures; they’re answering fundamental questions about the universe.
Key discoveries include:
– Confirming the accelerating expansion of the universe (which led to a Nobel Prize).
– Directly imaging planets orbiting other stars for the first time.
– Studying the supermassive black hole at the center of our Milky Way galaxy.
– Mapping the distribution of galaxies and the large-scale structure of the cosmos.
– Analyzing the atmospheres of planets in our own solar system, like Jupiter and Saturn.
The work done here literally changes our textbooks. It pushes the boundaries of what we know about space, time, and our place in the cosmos. The data from these telescopes is used by thousands of scientists around the globe.
The Future of Astronomy on Mauna Kea
The landscape for astronomy on Mauna Kea is evolving. The focus is shifting from building new structures to upgrading existing ones and being better stewards of the land. The conflict over the proposed Thirty Meter Telescope (TMT) has been a major turning point.
If completed, the TMT would be one of the world’s largest and most advanced telescopes. However, its construction has been halted for years due to sustained peaceful protests by Native Hawaiian protectors (kiaʻi) who view the project as a desecration. The future of the TMT on Mauna Kea remains uncertain, and the project is considering an alternative site in the Canary Islands.
Regardless of the TMT’s outcome, the existing telescopes on Mauna Kea will continue to operate for decades to come. They are constantly being fitted with new cameras and spectrographs, keeping them at the forfront of technology. The mission now is to balance world-class science with meaningful respect for Hawaiian culture and the environment.
Visiting Mauna Kea’s Summit
Many visitors to the Big Island hope to see the telescopes. It’s an amazing experience, but it requires planning and caution.
- Acclimatize: The altitude is serious. Spend at least 30 minutes at the Onizuka Center for International Astronomy Visitor Information Station (at 9,200 feet) to adjust. Do not proceed if you are pregnant, have heart or respiratory problems, or have scuba dived within the last 24 hours.
- Vehicle: You need a 4-wheel drive vehicle to drive the steep, unpaved summit road. Rental car companies often prohibit this.
- Guided Tours: The safest and easiest option is to book a commercial tour. They provide transportation, parkas, and guidance.
- Respect: Remember you are on sacred land. Stay on marked roads and paths. Do not disturb any rocks or natural features. The telescopes are working research facilities; public access inside is very limited and usually not allowed.
The best time to visit is for sunset, but be prepared for extremely cold and windy conditions. Temperatures are often below freezing.
FAQ Section
How many observatories are on Mauna Kea?
There are 12 active observatory facilities on the summit. Historically, 13 have been built, with one being decommissioned.
What is the largest telescope on Mauna Kea?
The twin Keck telescopes are the largest optical/infrared telescopes, each with a 10-meter mirror. The James Clerk Maxwell Telescope is the largest single-dish submillimeter telescope.
Can you go inside the telescopes on Mauna Kea?
General public access inside the working telescopes is extremely rare. The visitor station at 9,200 feet offers excellent educational programs and nighttime stargazing.
Why is there controversy about telescopes on Mauna Kea?
Mauna Kea is the most sacred site in Native Hawaiian culture. The construction and presence of large industrial facilities on the summit is seen by many as a profound disrespect and desecration of a holy place.
Are they building any new telescopes on Mauna Kea?
The proposed Thirty Meter Telescope (TMT) is planned, but its construction has been delayed for years due to legal challenges and protests. The current management plan requires decommissioning older telescopes before new ones are built.
How tall is Mauna Kea?
It is 13,803 feet (4,207 meters) above sea level. From its base on the ocean floor, it is over 33,000 feet tall, making it taller than Mount Everest.
In conclusion, the question of how many telescopes on Mauna Kea there are has a precise answer—twelve active ones—but it opens a door to a much larger story. It’s a story of human curiosity and our quest to understand the universe, set against the backdrop of a sacred mountain and a living culture. The future of this unique place will depend on finding a balance that honors both the stars above and the land below. The lessons learned here will shape how we pursue science in other sensitive environments, both on Earth and beyond.