Keck Observatory: The Most Scientifically Productive Telescopes

Keck Observatory
Keck I and Keck II Telescopes at the Mauna Kea Observatories at Sunset on the Big Island of Hawaii.

 Getty Images / Julie Thurston Photography

The W.M. Keck Observatory and its two ten-meter-wide telescopes sit high atop the Mauna Kea volcanic mountain in Hawai'i. These twin telescopes, which are sensitive to optical and infrared light, are among the world's largest and most productive instruments. Each night, they enable astronomers to peer at objects as close as worlds of our own solar system and as far away as some of the earliest galaxies in the cosmos.

Fast Facts: Keck Observatory

  • Keck Observatory has two ten-meter mirrors, each made up of 36 hexagonal-shaped elements that work together as a single mirror. Each mirror weighs 300 tons and is supported by 270 tons of steel. 
  • The volume of each telescope dome is more than 700,000 cubic feet. The domes are chilled throughout the day and kept at or below freezing temperatures to prevent distortion of the mirrors by heat.
  • Keck Observatory was the first major facility to use adaptive optics and laser guide stars. It now uses nearly a dozen instruments to image and study the sky. Future instruments include a planet finder and a cosmic mapper.

Keck Telescopes Technology

The W.M. Keck Observatory uses cutting-edge instruments to observe the universe, including some that help it dissect the light from distant objects. These spectrographs, along with infrared cameras, keep Keck at the forefront of astronomy research. In recent years, the observatory has also installed adaptive optics systems that help its mirrors compensate for the movement of the atmosphere that can blur the view. Those systems use lasers to create "guide stars" high in the sky.

Keck Observatory laser guide star.
A laser guide star being propagated from the Keck II telescope. This is used to help "clarify" the view for the telescope using adaptive optics. Keck Observatory

The adaptive optics lasers help measure the atmospheric motions and then correct that turbulence using a deformable mirror that changes shape 2,000 times per second. The Keck II telescope became the first large telescope worldwide to develop and install an AO system in 1988 and was the first to deploy lasers in 2004. The systems have provided a huge improvement in image clarity. Today, many other telescopes use adaptive optics to improve their views, too.

Keck Mirror.
The Keck 1 mirror. It is 10 meters across and made of 36 segments.  W. M. Keck Observatory

Keck Discoveries and Observations

More than 25 percent of observations made by US astronomers are done at the Keck Observatory and many of them approach and even surpass the view from the Hubble Space Telescope (which does its observing from high above Earth's atmosphere).

Keck Observatory allows viewers to study objects in visible light and then beyond, into the infrared. That wide range of observation "space" is what makes Keck so scientifically productive. It opens up a realm of interesting objects to astronomers that can't be observed in visible light.

Among them are starbirth regions similar to the familiar Orion Nebula and hot young stars. Not only do the newborn stars glow in visible light, but they heat up the clouds of material that formed their "nests." Keck can peer into the stellar nursery to see the processes of starbirth. Its telescopes allowed observations of one such star, called Gaia 17bpi, a member of a class of hot young stars called "FU Orionis" types. The study helped astronomers gather more information about these newborn stars still hidden in their birth clouds. This one has a disk of material that "falls into" the star in fits and starts. That causes the star to brighten every once in a while, even as it is growing. 

Outbursting star.
An artist's concept of an outbursting young star like the one studied at Keck. It is still buried in its cloud of gas and dust, which is spinning with it. Occasionally material is funneled onto the star via its magnetic fields. That temporarily brightens the star. IPAC

At the other end of the universe, the Keck telescopes have been used to observe an extremely distant cloud of gas that existed shortly after the birth of the universe, some 13.8 billion years ago. This distant clump of gas isn't visible to the naked eye, but astronomers could find it using specialized instruments on the telescope to observe a very distant quasar. Its light was shining through the cloud, and from the data, astronomers discovered that the cloud was made of pristine hydrogen. That means it existed at a time when other stars had not yet "polluted" space with their heavier elements. It's a look at conditions back when the universe was only 1.5 billion years old. 

Keck Observatory
This simulation of galaxies and gas in the early universe helps astronomers using Keck to study distant gas clouds that existed in the very early and distant universe. TNG Collaboration 

Another question that Keck-using astronomers want to answer is "how did the first galaxies form?" Since those infant galaxies are very far away from us and are part of the distant universe, observing them is difficult. First, they are very dim. Second, their light has been "stretched" by the expansion of the universe and, to us, appears in the infrared. Yet, understanding them can help us see how our own Milky Way formed. Keck can observe those distant early galaxies with its infrared-sensitive instruments. Among other things, they can study the light being emitted by hot young stars in those galaxies (emitted in the ultraviolet), which is re-emitted by clouds of gas surrounding the youthful galaxy. This gives astronomers some insight into conditions in those distant stellar cities at a time when they were mere infants, just starting to grow. 

Keck Observatory History

The history of the observatory stretches back to the early 1970s. That's when astronomers began looking at building a new generation of large ground-based telescopes with the largest mirrors they could create. However, glass mirrors can be quite heavy and ponderous to move. What the scientists and engineers wanted were light-weight ones. Astronomers involved at the University of California and Lawrence Berkeley Labs were working on new approaches to building flexible mirrors. They came up with a way to do it by creating segmented mirrors that could be angled and "tuned" to create one larger mirror. The first mirror, called Keck I, began observing the skies in May 1993. Keck II opened in October 1996. These reflecting telescopes have been in use ever since.

Since their "first light" observations, both telescopes have been part of the latest generation of telescopes that use advanced technology for astronomical studies. Currently, the observatory is used not only for astronomical observations, but also to support spaceflight missions to planets such as Mercury, and the upcoming James Webb Space Telescope. Its outreach is unmatched by any other current large telescope on the planet.

The W.M. Keck Observatory is managed by the California Association for Research in Astronomy (CARA), which includes cooperation with Caltech and the University of California. NASA is also part of the partnership. The W.M. Keck Foundation provided funding for its construction.


  • Image Gallery: Keck.
  • "News & Events from the IfA.” Measurement and Uncertainty,
  • “Up Above the World So High.” W. M. Keck Observatory,