Keck Observatory: Twin Telescopes on Mauna Kea
The Keck Observatory sits atop Mauna Kea on the Big Island of Hawaii.
Credit: NASA/JPL

The twin telescopes at the W.M. Keck Observatory are the largest optical and infrared telescopes in the world, according to the website for the telescopes. The observatory is located atop Mauna Kea, a dormant volcano in Hawaii.

The 10-meter telescopes are used regularly by professional astronomers. The mirrors for each telescope are actually not a single piece, but 36 parts that work together similarly to a single mirror. 

“In the middle of the Pacific Ocean, Hawaii Island is surrounded by thousands of miles of thermally stable seas,” the Keck Observatory wrote on its website. 

“The 13,796-foot Mauna Kea summit has no nearby mountain ranges to roil the upper atmosphere. Few city lights pollute Hawaiian night skies, and for most of the year, the atmosphere above Mauna Kea is clear, calm and dry.”

The primary mirror assembly of the 10-meter Keck II telescope is made of 36 parts that can adapt to atmospheric conditions.
The primary mirror assembly of the 10-meter Keck II telescope is made of 36 parts that can adapt to atmospheric conditions.
Credit: Andrew Cooper/W. M. Keck Observatory



Funding for the telescopes comes from a philanthropic organization known as the W.M. Keck Foundation. The entity was created in 1954 by William Myron Keck, who founded the Superior Oil Company, according to the foundation’s website. 

“Mr. Keck envisioned a philanthropic institution that would provide far-reaching benefits for humanity,” the foundation stated. “By taking a bold, creative approach to grantmaking, he created a legacy that the foundation proudly upholds today.”

The foundation’s mandate includes funding science, and in 1985 it granted $70 million ($155 million in 2014 dollars) to construct the first telescope, Keck I. During construction, $68 million came through for the second telescope, Keck II. The telescopes began their science work in 1993 and 1996 respectively, according to the telescope website. [Related: Keck Observatory: Cosmic Photos From Hawaii's Mauna Kea]

The telescopes’ arsenal of instruments includes several for optical wavelengths and others for infrared. The optical instruments include (but are not limited to) DEIMOS or the Deep Extragalactic Imaging Multi-Object Spectrograph, which can pick up spectral information from 1,200 objects simultaneously, and HIRES (High Resolution Echelle Spectrometer) that can examine the colors of starlight.

Examples of infrared instruments include the laser adaptive optics system, and NIRSPEC (The Near Infrared Spectrometer). Some of NIRSPEC’s scientific investigations include looking at radio galaxies that are very far from Earth (which means they are older as per the Big Bang Theory, which says the universe arose from a singularity and is expanding ever since.) NIRSPEC can also be used to learn more about brown dwarfs, which are objects that are considered “failed stars” — immense gas giants that are not quite large enough to start nuclear fusion.

Beaming up sharp images

According to the telescope website, the Keck II telescope is the first in the world to use an adaptive optics system. This type of a system is intended to change the shape of the mirror to account for changes in the atmosphere. 

The atmosphere can blur the appearance of distant stars, making it difficult for astronomers to make accurate measurements unless they rise above the air. (This is one reason that scientists enjoy using telescopes such as the Hubble Space Telescope or the Spitzer Space Telescope.)

Because the atmosphere changes so quickly, Keck has to change form rapidly as well. The telescope can alter its mirror 2,000 times each second, making images 10 times clearer than they would be without the system.

The telescope relies on a laser to make the measurements on how to change, which is an improvement over the old method: using a bright star, which isn’t easy to achieve as this is only possible in about 1 percent of the sky.

“Astronomers developed laser guide star adaptive optics using a special-purpose laser to excite sodium atoms that sit in an atmospheric layer 90 kilometers above Earth,” Keck stated. “Exciting the atoms in the sodium layers creates an artificial ‘star’ for measuring atmospheric distortions and allows adaptive optics to produce sharp images of celestial objects positioned nearly anywhere in the sky.”

Notable discoveries

Keck’s twin telescopes have made a host of discoveries since construction finished. Among them was assisting another observatory with watching the first exoplanet “transit” across its parent star in 1999. 

This occurred after Keck did measurements of star HD 209458 and noted that the star appeared to wobble, as though there was a planet altering its movements. The science team then asked others using the privately funded Fairborn Observatory in Arizona to watch for a transit across the star’s face, which occurred.

Another discovery was figuring out how stars move in the Andromeda Galaxy, a prominent galaxy that is 2.5 million light-years from Earth, making it a very close neighbour. This was important because it helped astronomers understand just how immense this galaxy is. The diameter ended up being three times bigger than thought before, at 220,000 light-years.

Keck also participated in a research project involving several telescopes, which looked at supernovas (star explosions) across the universe. The aim was to use them to calculate how fast the universe is expanding. Results showed that the universe is actually accelerating as it grows, perhaps pushed along by “dark energy” — a little-understood concept that may (along with dark matter) make up most of the universe. [Related: 10 Amazing Space Discoveries by the Keck Observatory]

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