Mauna Kea Astronomy and the Keck Telescopes

Mauna Kea Astronomy and the Keck Telescopes

[Illustration: Overview of observatories atop Mauna Kea]

 

Wouldn’t it be great to be able to look back in time, and see all the way back to the beginning of the universe?  That’s exactly what the Keck Telescopes allow scientists to do every day atop Mauna Kea’s summit on Hawai‘i Island, where researchers use the massive but precise instruments to explore the early universe through astronomical studies. 

 

Mauna Kea, kuahiwi ku ha‘o i ka mālie.

Mauna Kea, standing alone in the calm.

                                                (Pukui: 2147-234)

 

Amidst a moonscape of blackened craters and lava cinder cones, the Keck telescopes are just two of the many gleaming white and silver domes atop Mauna Kea.  The summit of Mauna Kea supports 13 major observatories operated by 11 countries. 

These telescopes comprise the world’s largest cluster of astronomical observatories.  With precision and power unmatched anywhere on the planet, the international observatories atop Mauna Kea have come a long way from the first telescopes invented by Galileo nearly 400 years ago.

 

Mauna Kea’s Summit—Ideal Observatory Location

The summit of Mauna Kea is considered the best site on Earth for astronomy.  Above 40% of Earth’s atmosphere, Mauna Kea’s summit is completely surrounded by thermally stable ocean and generally free from the turbulence and light that interfere with telescopes at lower altitudes. 

At Mauna Kea’s 13,796-foot (4,205-m) summit there is 38% less oxygen than at sea level, and it is well above the tropical inversion cloud layer that effectively isolates the peak from moist sea-level air.

The University of Hawai‘i leases the summit land of Mauna Kea from the State of Hawai‘i.  The telescope facilities on the summit constitute the Mauna Kea Science Reserve Complex. 

Observing Assistants operate the telescopes for astronomers, cosmologists, astrophysicists and other researchers who gather scientific data from the instruments.  Research teams usually work for one to four nights according to pre-approved time allocations.

 

The Keck Telescopes

The most prominent telescopes atop Mauna Kea are the twin Keck Telescopes, which became operable in 1992 and 1996.  The Keck Telescopes are the largest optical-infrared telescopes in the world.  The domes cost $70 million each, and were funded by the W.M. Keck Foundation. 

The founding partners of the Keck telescopes are the University of California and the California Institute of Technology.  Astronomers from those institutions as well as from the University of Hawai‘i (and others) have used the Keck telescopes to make many important discoveries. 

In 1996, the National Aeronautics and Space Administration (NASA) became part of the Keck partnership, particularly the interferometer project (see below).

Each Keck dome is 111 feet (33.8 m) tall and contains more than 700,000 cubic feet (18,833 cu. m) of volume.  Despite their huge size, the Keck telescopes are finely engineered precision instruments.  For example, the main moveable 300-ton (272-mton) component of each dome is so perfectly balanced it may be moved with one hand. 

The Hubble Space Telescope is above Earth’s atmosphere, and so it may receive sharper images than the Keck Telescopes.  However the Hubble’s mirror (at 2.4 meters) is only 1/25th the size of the Keck mirrors, and thus is not able to gather as much light as the Keck Telescopes.  The result is that the Keck Telescopes can see objects much farther away.

The segmented mirror of each Keck Telescope is a perfect parabolic reflecting surface 32.8 feet (10 meters) in diameter.  Each mirror is made up of 36 smaller hexagonal (6-sided) mirrors, each 6 feet (1.8 m) across.  These smaller mirrors are individually controlled by computers, so that all of the mirrors work in concert as if they are one giant mirror—quite an engineering feat. 

The surfaces of the Keck mirrors are polished so incredibly smooth that if they were expanded to the size of Earth, any deformities would still only measure about 3 feet (.9 m) high.  To counteract gravity’s on the mirrors, computer-controlled precision pistons and sensors adjust the mirror segments individually (twice every second), to an accuracy of 4 nanometers, which is about 1/1000th the diameter of a human hair. 

The interiors of the Keck domes are chilled to near freezing in the daytime, so that when they are opened in the nighttime they are already at ambient outdoor temperature.

 

Keck Adaptive-Optics Interferometry Project

The Keck II uses a new adaptive optics system in which deformable mirrors may change shape 670 times per second to cancel out atmospheric distortion.  This produces images ten times sharper than previous images. 

The new adaptive optics system has also resulted in new discoveries, including the clearest pictures ever of Neptune.  Also recently discovered were orbits of stars around what is thought to be a Black Hole at the center of our Milky Way Galaxy.

Using an instrument called an interferometer, engineers and scientists succeeded in combining the light-gathering powers of the two 10-meter (32.8-ft) Keck telescopes in March of 2001. 

The interferometer manipulates light waves so that their peaks match, creating a much higher peak (similar to what occurs with ocean waves).  This is called constructive interference, and it creates a much stronger signal, allowing scientists to produce images with a much greater level of detail. 

The Keck project is being completed by the Jet Propulsion Laboratory and the California Association for Research in Astronomy, and is financed by NASA.  A series of small outrigger telescopes as well as a series of underground tunnels combine the light from the two giant Kecks, forming the world’s largest optical interferometer.

Researchers will continue to fine-tune the interferometer, producing a single high-resolution image equal in sharpness to what would normally require a mirror about 279 feet (85 km) across. 

By combining the power of the twin Keck telescopes, researchers hope to study Earth-like planets orbiting nearby stars.  Another major goal of Keck’s adaptive-optics/interferometry project is learning about the formation of solar systems by analyzing dust clouds surrounding nearby stars.

On May 19 and 20, 2003, using adaptive optics and the interferometer, researchers were able to use the twin Keck telescopes to take measurements of a black hole in a galaxy named NGC 4151 about 40 million light years from Earth, and about the same size as the Milky Way.  The black hole in NGC 4151 is about ten times as large as the black hole at the center of the Milky Way Galaxy.

The combined Kecks, with a precision ten times as sensitive as a single Keck, were also used to study a star 450 light years distant from Earth.  The dual Keck telescopes were also used in 2003 to obtain the best view to date of the universe’s most primordial objects, including an ancient galaxy where stars began forming when the universe was only about 2 billion years old. 

The view of this ancient star cluster, known as the Lynx Arc, is by coincidence greatly enhanced by a process called gravitational lensing

 

Keck Discoveries

A variety of scientific instruments designed for the Keck I and Keck II telescopes perform different tasks for researchers investigating distant galaxies.  Particularly in the infrared portion of the light spectrum, the Kecks have explored the farthest limits of space ever reached by the eyes of humans. 

In 2002, the Keck broke its own record for sighting the most distant objects ever seen when it viewed a galaxy estimated to be 15.5 billion light years away. 

An international team of astronomers with the University of Hawai‘i was able to view the distant galaxy by using a galaxy cluster about six billion light years away to magnify the light in a process known as gravitational lensing.  One light year is the distance light travels in one year, which is about 5.9 trillion miles (9.5 trillion kilometers). 

Cosmologists and astronomers utilize the Keck telescopes and other observatories atop Mauna Kea to investigate Earth’s moon, our solar system’s planets, the Milky Way Galaxy, and far beyond. 

The Keck telescopes are also used to find new planets, and by 2002 almost 100 had been found.  Before the Keck I opened in 1992 no planets outside our own solar system had been discovered.  By 2002, the Keck telescopes had been used to find nearly 100 planets around at least 70 distant stars, some as far as 250 light years away. 

In April of 2002, two separate Keck astronomy research teams reported the strongest evidence to date of planetary orbits in a solar system around a relatively nearby star, Beta Pictoris, which is only about 63 light-years away from Earth and visible with the naked eye. 

In October or 2002 the linked telescopes were able to view swirling particles around a young star said to be more similar to our own solar system than any previous objects viewed.

The Keck telescopes and other Mauna Kea observatories are used to conduct research on the evolution of galaxies, planetary and star-forming nebulae, supernova remnants, star clusters, double stars, quasars, and intergalactic gases as well as red, white and brown dwarfs.  Red dwarfs are the lowest mass stars, while brown dwarfs are bigger than planets yet smaller than stars, and lack the internal energy (core nuclear reactions) of stars.

One of the most interesting recent astronomical observations seen with a telescope from atop Mauna Kea Volcano was another volcano, called Surt, which was observed actively erupting on Io, one of Jupiter’s four large moons.  Io is the solar system’s most volcanically active body. 

Imke de Pater, a Professor of Astronomy at the University of California at Berkeley, along with post-doctoral researcher Franck Marchis, used an infrared camera along with the Keck II telescope to capture images of the eruption of Surt Volcano on February 22, 2001.

The lava erupting from Surt Volcano was estimated to be about 2000° F (1,100° C), which is slightly hotter than the lava erupting from Hawai‘i Island’s Kīlauea Volcano. 

The Surt eruption covered an area of about 30 miles (48 km) across, totaling about 735 square miles (1,900 sq. km) in all.  On Earth, larger eruptions have occurred, such as an ancient eruption in India that covered an estimated 200,000 square miles (518,000 sq. km), but the eruption of Surt is the largest ever actually seen by humans.  Information about the Surt eruption was published in the November 2002 issue of Icarus, a planetary journal.

Io’s volcanoes were monitored by the Galileo spacecraft (a project of NASA), which orbited Jupiter from 1995 to 2003.

 

Other Telescopes Atop Mauna Kea:

·                    Gemini Northern 8-meter optical/infrared telescope (1999).

·                    James Clerk Maxwell 15-meter submillimeter telescope (1986).

·                    Caltech 10.4-meter submillimeter telescope (1986).

·                    Canada-France-Hawai‘i 3.6-meter optical/infrared telescope (1979).

·                    NASA IRTF 3-meter infrared telescope (1979).

·                    United Kingdom 3.8-meter infrared telescope (1979).

·                    University of Hawai‘i 2.2-meter optical/infrared telescope (1970).

·                    University of Hawai‘i .6-meter optical telescope #1, and #2 (1968, 1969).

·                    Subaru 8.3-meter optical/infrared Japan National telescope (1999).

·                    Very Long Baseline Array Antenna 25-meter radio telescope (1992).

·                    Smithsonian Submillimeter Array 8 6-meter (2003).

 

Jupiter’s Moons

In June of 2002, astronomer David Jewitt and graduate student Scott Shepard of the University Institute of Astronomy announced that they had used digital imaging technology and the Canada-France-Hawai‘i telescope to discover 11 new moons around the planet Jupiter, the largest planet in our solar system. 

At that time Jupiter already had 28 known moons, 11 of which were found in January of 2001 by the same two researchers.  The new discoveries raised to 39 Jupiter’s total number of known moons, most of which are only about 2 miles (3.2 km) in diameter.  The researchers’ results were confirmed using the University of Hawai‘i 2.2-meter telescope.

More discoveries occurred in late 2002 and into 2003, raising Jupiter’s known moons to more than 47.  The discoveries utilized the University of Hawai‘i 2.2-meter telescope as well as the Canada-France-Hawai‘i 3.6-meter telescope and the Subaru 8.3-meter telescope, which have digital cameras that are among the largest in the world. 

In February of 2003, the Harvard-Smithsonian Center for Astrophysics utilized the Canada-France-Hawai‘i telescope and a telescope in Chile to discover three new moons around Neptune. 

In 2003 an instrument, called “Megaprime,” the world’s largest telescope-mounted camera, was developed for the Canada-France-Hawai‘i telescope to provide an emerging technology called high-resolution wide-field imaging.

Megaprime utilizes the “Megacam,” the newly-crowned largest digital camera in the world, which is capable of viewing about one degree by one degree of sky (the full moon is about one fourth of one degree), and can take pictures with 350 million pixels (a pixel is the smallest element of an image). 

The Megacam is more than 100 times as powerful as high-quality digital cameras available commercially.  The high-resolution, wide-field imaging technology makes it highly likely that numerous new moons will soon be discovered around the solar system’s planets, continuing the work begun by Galileo when he discovered Jupiter’s four large moons—Io, Europa, Ganymede, and Callisto—in 1610.

 

Submillimeter Research

Dedicated in November of 2003, the Smithsonian Submillimeter Array is the first imaging telescope of its kind, built to allow astronomers to study submillimeter waves.  The submillimeter region of the electromagnetic spectrum is concerned with wavelengths that have more energy than microwaves (commonly used in home ovens) but less energy than infrared light. 

Only recently has the technology been available to produce the precisely shaped antennas and the extremely sensitive receivers required for submillimeter research. 

The submillimeter waves emanating from distant objects are received by an array of satellite dishes, and linked by interferometry, allowing scientists to study: distant galaxies more than 13 billion light years away; planets and comets within the Milky Way; stars in the Milky Way that are still in their formative stages; and other astronomical objects. 

The Submillimeter Array was built by Taiwan’s Institute of Astronomy and Astrophysics in partnership with the University of Hawai‘i’s Institute for Astronomy (which provided the space on Mauna Kea for the facility), and the Smithsonian Institution’s Astrophysical Observatory, based in Cambridge, Massachusetts, which funded 6 of the dishes. 

Two of the dishes were funded by the Academia Sinica Institute of Astronomy and Astrophysics of Taiwan, which has a 15% interest in the overall project.

A specialized array of eight movable 6-meter antennas allow various configurations as optical fibers carry the radiation from each antenna to a central focus, where the signal is correlated and combine to produce images with a quality of resolution comparable to the world’s best optical telescopes. 

The facility’s many antennae working together at their widest separation can produce an image with details comparable to that produced by a single telescope with a diameter of 1,600 feet (488 m).  A forklift can move the antennae to different configurations as needed. 

The new array also produces images of objects up to 30 times smaller than can be viewed using Mauna Kea’s other submillimeter telescopes (the James Clerk Maxwell 15-meter submillimeter telescope, and the Caltech 10.4-meter submillimeter telescope. 

The Submillimeter Array will be linked to the James Clerk Maxwell Telescope as well as the Caltech Submillimeter Observatory.

 

Infrared Megapixel Camera

In 2003, an innovative new technology was used to create a 16-megapixel infrared camera mounted on the University of Hawai‘i 2.2-meter optical/infrared telescope, increasing sky coverage by a factor of 16. 

These new cameras make the University of Hawai‘i 2.2-meter optical/infrared telescope the most powerful infrared imaging telescope in the world. 

Eventually this new megapixel technology will also likely be employed on the Gemini Northern 8-meter optical/infrared telescope and Canada-France-Hawai‘i 3.6-meter optical/infrared telescope.

 

 

Very Long Baseline Array

The 25-meter (82-foot) radio telescope atop Mauna Kea is part of the Very Long Baseline Array (VLBA), which was used on September 8, 2002 to measure the speed of gravity, or more technically, the speed at which gravity propagates, thus finally quantifying one of the last of the unmeasured fundamental constants. 

The Very Long Baseline Array (VLBA) uses a new technology known as Very Long Baseline Interferometry (VLBI), which has finally made it possible to achieve the extremely high precision needed to measure the speed of gravity.  Also utilized in the gravity measurement was a 100-meter (328-foot) radio telescope in Effelsberg, Germany.

The gravity propagation speed measurement was made possible by a celestial alignment in which Jupiter came close to the path of radio waves being produced by a quasar named J0842+1835 (quasars are extremely distant and exceptionally bright objects thought to be nuclei of galaxies).

The researchers involved in the gravity study, including Ed Fomalont at the National Radio Astronomy Observatory in Charlottesville, Virginia and Sergei Kopeikin at the University of Missouri-Columbia, concluded that the speed at which gravity propagates is within 20% of the speed of light.  Einstein had theorized that it was equal to the speed of light, while Newton had considered the force of gravity to be instantaneous. 

The recent measurements of gravity’s propagation speed have strong implications for unified field theorists attempting to join particle physics with electromagnetic theory and Einstein’s general theory of relativity.

The 240-ton (218-mton) VLBA antenna on Mauna Kea is part of an array of antennae across the United States, along with one antenna on St. Croix in the Caribbean.  Digital tapes record the data at each antenna site, and then the information is analyzed at the array’s Socorro Operations Center in New Mexico.

[Photograph: Keck Telescope showing outriggers, snow]