Keck Observatory

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The domes of the two Keck telescopes
Keck-I and -II with open domes

The W. M. Keck Observatory is part of the Mauna Kea Observatory at the summit of the 4200 m high dormant volcano Mauna Kea on the island of Hawai'i .

It houses two identical mirror telescopes , each of which has a main mirror (composed of 36 smaller, hexagonal segments) with a diameter of 10 m and which were the largest optical telescopes in the world until July 2007. They were replaced by the Gran Telescopio Canarias , the mirror diameter of which is 10.4 m. The mirror carriers for these telescopes were made from Zerodur glass ceramic by Schott AG in Mainz . The Keck-I telescope was put into operation in 1993, the Keck-II telescope followed in 1996. The two telescopes can also be operated together as an optical interferometer . Keck I and Keck II have adaptive optics .

The establishment goes back to a donation of the WM Keck Foundation in the amount of 140 million US dollars . The observatory is operated jointly by the California Institute of Technology , the University of California and the US space agency NASA .


Construction work on Keck I began in 1985. The first light reached Keck I in 1990. It was put into scientific operation in 1993. Due to later donations, construction of the identical Keck II telescope started in 1991. The first light for Keck II was in 1996.


Primary mirror

The main mirrors of the two Keck telescopes are 10 m in diameter. The primary mirrors are parabolic in shape. They consist of 36 small hexagonal segments. Each of these segments has its own suspension and can be individually adjusted to within 4 nanometers. This at the time atypical but revolutionary form of honeycomb construction was chosen because the mirror is lighter and can be held better by the support structure. It can therefore also be adapted to the deformation caused by gravity.

A system to suppress air turbulence in the atmosphere was installed in 1999. A reference star or reference point (a point in the atmosphere generated by a laser) is aimed at in the vicinity of the observed object. A computer then calculates the adjustment of the individual segments twice per second. This creates an almost perfect picture.

Light path

With the Keck telescope, the incident light is reflected by a main mirror (primary mirror) onto a secondary mirror, which is smaller than the main mirror and is located in the center of the tube. This reflects the light either through a hole in the main mirror (this type of telescope is called a Cassegrain reflector) or via a further mirror (tertiary mirror) that is mounted on the main mirror and reflects the light to the side (Nasmyth reflector), where most of the instruments are located . The focal point of the main mirror is 17.5 m. The secondary and tertiary mirrors only reflect the light in order to keep the design of the telescope more compact. Lenses at the focal point guide the light rays parallel again. Behind them are either cameras or instruments with which the incident light is examined.


The Keck Observatory has a wealth of high-tech instruments. These examine light in the optical and near-infrared range. A large part of these instruments are spectrographs. They divide the light into its various components and then examine them.

  • MOSFIRE (Multi-Object Spectrograph For Infra-Red Exploration) : MOSFIRE is the latest spectrograph and observes many celestial bodies simultaneously in the infrared and near-infrared range. At the same time it is also a camera.
  • DEIMOS (Deep Extragalactic Imaging Multi-Object Spectrograph): This spectrograph can simultaneously examine the spectra of up to 1200 objects.
  • HIRES (High Resolution Echelle Spectograph): HIRES is the largest, most complex and most precise instrument of the Kecks. Many groundbreaking discoveries were made with him. It has discovered most of the exoplanets and evidence for the big bang theory so far.
  • NIRC-2 (Near Infra-Red Camera): NIRC is a camera that photographs celestial objects in the near infrared range. With NIRC one observes very distant galaxies.
  • NIRSPEC (Near Infra-Red Spectrograph): NIRSPEC observes brown dwarfs, galactic centers, red-shifted radio galaxies, the solar system, the structure of celestial objects and radiation-intensive regions in the near infrared range.
  • OSIRIS (OH- Suppressing Infra-Red imaging Spectrograph): OSIRIS observes objects in the near infrared range. It can ignore the part of the atmosphere that glows brighter due to OH molecules. So it can see even more objects in the sky.
  • LRIS (Low Resolution Imaging Spectograph): LRIS can still evaluate very weak light and look to the edge of the explored universe. It observes galaxies, galaxy clusters and quasars.
  • Keck interferometer: The telescope can also be used as an optical interferometer. The light from both telescopes is brought together and evaluated in a central room. If you use the telescopes in parallel, they no longer only have the resolution of a single mirror, but that of a mirror that extends from the edge of one mirror to the edge of the other (85 m by 10 m). This allows you to look further into the universe in greater detail.


The Keck telescopes observe objects in the visible and near infrared range. Due to their high resolution and interferometry, they can explore objects far inside the universe. The oldest and most distant galaxies known to date were discovered with the telescopes. The Kecks tracked down the first exosolar planets orbiting a star. More than half of all exoplanets were discovered with Keck. Using the telescopes, scientists have also used star movements to discover that there is a supermassive black hole in the center of the Milky Way. In addition, the planets of the solar system are observed and interesting observations are checked and further explored by other institutions.

See also


  • Peter Wizinowich et al: Performance of the WM Keck Observatory Natural Guide Star Adaptive Optic Facility: the first year at the telescope. Proc. SPIE Vol. 4007, pp. 2-13, Adaptive Optical Systems Technology, 2007, bibcode : 2000SPIE.4007 .... 2W , PDF.

Web links

Commons : Keck Observatory  - collection of images, videos and audio files

Individual evidence

  1. About the current Keck AO systems. At: Retrieved March 3, 2011.

Coordinates: 19 ° 49'35 "  N , 155 ° 28'29"  W.