W. M. Keck Observatory

W. M. Keck Observatory

The Keck observatory domes atop Mauna Kea
Alternative names	Keck telescope
Part of	Mauna Kea Observatories
Location(s)	Hawaii
Coordinates	19.82636°N 155.47501°W / 19.82636; -155.47501
Organization	California Association for Research in Astronomy dba W. M. Keck Observatory
Altitude	4,145 m (13,600 ft)
Wavelength	Optical, near-infrared
Built	Keck I 1993, Keck II 1996
First light	24 November 1993, 23 October 1996
Telescope style	Reflector
Number of telescopes	2
Diameter	10 m (33 ft) each
Angular resolution	0.04 to 0.4 arcseconds for individual telescopes, depending on target and instruments used
Collecting area	76 m2 (820 sq ft) each
Focal length	17.5 m (f/1.75)
Mounting	Alt/az
Enclosure	Spherical
Website	www.keckobservatory.org
Location of W. M. Keck Observatory
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The W. M. Keck Observatory is a two-telescope astronomical observatory at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. The primary mirrors of each of the two telescopes are 10 meters (32.8 ft (394 in)) in diameter, making them the second largest optical telescopes in the world, slightly behind the Gran Telescopio Canarias; however the Gran Canary telescope uses many smaller hexagonal mirrors to produce one large mirror, the hexagonal shape means that the scaling of the mirror is different, and while the diameter may be greater the area of the mirror is slightly less that the Keck. GTC wiki article contradicts it with 10.4 effective mirror size. And GTC website also has 10.4m size.|date=August 2013}}, thus making the Keck telescopes the largest observable telescope in the world. The telescopes can operate together to form a single astronomical interferometer.

Overview

In 1985, Howard B. Keck of the W. M. Keck Foundation gave $70 million to fund the design and construction of the Keck I Telescope. The key advance that allowed the construction of the Keck's large telescopes was the ability to operate smaller mirror segments as a single, contiguous mirror. In the case of the Keck each of the primary mirrors is composed of 36 hexagonal segments that work together as a single unit. The mirrors were made from Zerodur glass-ceramic by the German company Schott AG. On the telescope, each segment is kept stable by a system of active optics, which uses extremely rigid support structures in combination with adjustable warping harnesses. During observation, a computer-controlled system of sensors and actuators adjusts the position of each segment, relative to its neighbors, to an accuracy of four nanometers. This twice-per-second adjustment counters the effect of gravity as the telescope moves, in addition to other environmental effects that can affect the mirror shape.

Each Keck telescope sits on an altazimuth mount. During the design stage, computer analysis determined that this mounting style provides the greatest strength and stiffness for the least amount of steel, which totals about 270 tons per telescope. The weight of each telescope is about 300 tons.

The telescopes are equipped with a suite of instruments, both cameras and spectrometers that allow observations across much of the visible and near infrared spectrum.

Management

The Keck Observatory is managed by the California Association for Research in Astronomy, a non-profit 501(c)(3) organization whose board of directors includes representatives from Caltech and the University of California. Construction of the telescopes was made possible through private grants totaling more than $140 million provided by the W. M. Keck Foundation. The National Aeronautics and Space Administration (NASA) joined the partnership in October 1996, at the time Keck II commenced observations. The Keck I telescope began observations in May 1993.

Telescope time is allocated by the partner institutions. Caltech, the University of Hawaii System, and the University of California accept proposals from their own researchers. NASA accepts proposals from researchers based in the United States, while the National Optical Astronomy Observatory (NOAO) accept proposals from researchers around the world.

Instruments

The Keck II Telescope showing the segmented primary mirror

MOSFIRE

MOSFIRE is a third generation instrument for the W. M. Keck Observatory. MOSFIRE was delivered to the W. M. Keck Observatory on February 8, 2012 and “first light” on the Keck 1 telescope was obtained on April 4, 2012. A Multi-Object Spectrograph For Infra-Red Exploration and wide-field camera for the near-infrared (0.97 to 2.41 μm), MOSFIRE’s special feature is the cryogenic Configurable Slit Unit (CSU) that is reconfigurable under remote control in less than 6 minutes without any thermal cycling. Bars move in from each side to form up to 46 short slits. When the bars are removed MOSFIRE becomes a wide-field imager. The instrument was developed by teams from the University of California, Los Angeles (UCLA), the California Institute of Technology (Caltech) and the University of California, Santa Cruz, (UCSC). The Co- Principal Investigators are Ian S. McLean (UCLA) and Charles C. Steidel (Caltech), and the project was managed by WMKO Instrument Program Manager, Sean Adkins. MOSFIRE was funded in part by the Telescope System Instrumentation Program (TSIP), which is operated by AURA and funded by the National Science Foundation, and by a private donation to WMKO by Gordon and Betty Moore.

DEIMOS

The Deep Extragalactic Imaging Multi-Object Spectrograph is capable of gathering spectra from 130 galaxies or more in a single exposure. In “Mega Mask” mode, DEIMOS can take spectra of more than 1,200 objects at once, using a special narrow-band filter.

HIRES

The largest and most mechanically complex of the Keck’s main instruments, the High Resolution Echelle Spectrometer breaks up incoming starlight into its component colors to measure the precise intensity of each of thousands of color channels. Its spectral capabilities have resulted in many breakthrough discoveries, such as the detection of planets outside our solar system and direct evidence for a model of the Big Bang theory. This instrument has detected more extrasolar planets than any other in the world. The radial velocity precision is up to one meter per second (1.0 m/s). The instrument detection limit at 1 AU is 0.2 M_J.

LRIS

The Low Resolution Imaging Spectrograph is a faint-light instrument capable of taking spectra and images of the most distant known objects in the universe. The instrument is equipped with a red arm and a blue arm to explore stellar populations of distant galaxies, active galactic nuclei, galactic clusters, and quasars.

NIRC

The Near Infrared Camera for the Keck I telescope is so sensitive it could detect the equivalent of a single candle flame on the Moon. This sensitivity makes it ideal for ultra-deep studies of galactic formation and evolution, the search for proto-galaxies and images of quasar environments. It has provided ground-breaking studies of the Galactic center, and is also used to study protoplanetary disks, and high-mass star-forming regions.

NIRC-2

The second generation Near Infrared Camera works with the Keck Adaptive Optics system to produce the highest-resolution ground-based images and spectroscopy in the 1–5 micrometers (µm) range. Typical programs include mapping surface features on Solar System bodies, searching for planets around other stars, and analyzing the morphology of remote galaxies.

NIRSPEC

The Near Infrared Spectrometer studies very high redshift radio galaxies, the motions and types of stars located near the Galactic Center, the nature of brown dwarfs, the nuclear regions of dusty starburst galaxies, active galactic nuclei, interstellar chemistry, stellar physics, and Solar System science.

OSIRIS

The OH-Suppressing Infrared Imaging Spectrograph is a near-infrared spectrograph for use with the Keck II adaptive optics system. OSIRIS takes spectra in a small field of view to provide a series of images at different wavelengths. The instrument allows astronomers to ignore wavelengths where the Earth’s atmosphere shines brightly due to emission from OH (hydroxyl) molecules, thus allowing the detection of objects 10 times fainter than previously available. In January, 2012 OSIRIS was moved to the Keck I telescope.

Both Keck telescopes are equipped with laser guide star adaptive optics, which compensates for the blurring due to atmospheric turbulence. The first AO system operational on a large telescope, the equipment has been constantly upgraded to expand the capability. In addition, the Keck I and Keck II telescopes can work together as the Keck Interferometer. The 85-metre (279 ft) separation between the two telescopes gives them the effective angular resolution in one direction of an 85-metre (279 ft) mirror. Along this axis, the Keck Interferometer has a spatial resolution of 5 milliarcseconds (mas) at 2.2 µm, and 24 mas at 10 µm. In its most sensitive configuration, the interferometer would reach K=21 and N=10 mag in 1000 seconds of integration (SNR = 10 per baseline). The interferometer has several back-end instruments, allowing for a variety of observation types. The lack of additional outrigger telescopes makes the Keck Interferometer unsuitable for interferometric imaging, so work has concentrated on nulling interferometry and angular diameter measurements instead. In September 2005, the Keck Interferometer demonstrated nulling interferometry for the first time, with a modest null depth of 100 times.

The summit of Mauna Kea is considered one of the world's most important astronomical viewing sites. The twin Keck telescopes are among the largest optical/near-infrared instruments currently in use around the world.

The night sky and Keck laser for adaptive optics

W. M. Keck Observatory at sunset

See also

• Mauna Kea Observatories
• Very Large Telescope
• Gemini Observatory
• List of largest optical reflecting telescopes
• List of largest optical telescopes historically
• List of astronomical interferometers at visible and infrared wavelengths

External links

• W. M. Keck Observatory (official site)
• The Mauna Kea Observatory (official site)
• Keck Observatory Archive (KOA)
• Lawrence Berkeley Lab, Revolution in telescope design
• Indigenous Controversy
• Photos of Keck telescopes and other Mauna Kea observatories from "A Gentle Rain of Starlight: The Story of Astronomy on Mauna Kea" by Michael J. West. ISBN 0-931548-99-3.