Ever wonder what it’s like to be part of an astronomy department at a major university — what instruments the scientists use, and what research they’re doing? Peter V. Mason of the Cahill Center for Astronomy and Astrophysics at the California Institute of Technology in Pasadena offers Astronomy readers this glimpse into the studies going on at Caltech. This is the first in a series of blogs he will write for us. In this entry, Peter introduces us to some of the field observatories Caltech researchers use.
Mount Wilson 100-inch Telescope
The earliest major instrument in the Caltech array, the 100-inch telescope at Mt. Wilson is in the San Gabriel Range above Pasadena. This inspiration of George Ellery Hale was finished in 1917. The telescope was funded by the Carnegie Institute of Washington and operated by a Carnegie-Caltech consortium until 1986, when control went to the nonprofit Mount Wilson Institute. Caltech researchers and other professional astronomers still use the 100-inch telescope, which recently received adaptive optics. The observatory is open to public visits daily from 10 a.m. to 4 p.m., April through November, and also is home to a 60-inch telescope that is available to qualified amateurs. Those interested can contact the staff at www.mtwilson.edu/60in.php.
Palomar Mountain Hale Telescope
Caltech’s next venture into large telescopes was the 200-inch Hale Telescope on Palomar Mountain, about 100 miles (160 kilometers) southeast of Pasadena, at 5,500 feet (1,675m). Hale inspired this telescope as well. For 45 years (1948–1993), the 200-inch was the largest optical telescope in the world, until the completion of the 10-meter Keck Telescope in Hawaii. The Palomar Observatory is the site of four active telescopes; besides the 200-inch, a 60-inch, a 48-inch, and a 24-inch telescope are in use. All of these are available to professional astronomers only. The observatory is open daily for visitors, and guided tours operate on weekends.
The two Keck 10-meter telescopes atop Mauna Kea. Photo courtesy W. M. Keck Observatory
The peak of Mauna Kea on the island of Hawaii surely holds the grandest collection of large telescopes in the world. At about 13,700 feet (4,250m), it is the highest major astronomical site in the world, although the Chajnantor Observatory in the Andes (16,700 feet [5,080m]) is higher. On Mauna Kea, there are eight optical telescopes larger than 2.2 meters, topped by the two Caltech 10-meter Keck telescopes. The site also features three submillimeter telescopes: the 15-meter James Clark Maxwell telescope; the 10.4-meter Caltech Submillimeter Observatory; and the Submillimeter Array of eight telescopes, each 6 meters in diameter. There is also a receiver for the Very Long Baseline Array, with a dish 26 meters in diameter.
The Keck 10-meter telescopes have 36 segmented mirrors that scientists can actively align. Because of the large size of the primary mirror, the mount is of the simpler and stronger alt-azimuth configuration rather than the classical right-ascension-declination type. The use of computer-controlled pointing makes this feasible. An impressive accomplishment is the linking of the two telescopes as a single optical interferometer, the first combining very large telescopes in an array. The Keck 1 Telescope was the largest in the world from 1993 until 2009, when the 10.4-meter Gran Telescopio Canarias began operation.
The public may drive to these observatories, but they are advised to stop at the visitor center at 9,200 feet (2,800m) to acclimate themselves. Activity (including operating a telescope) is very demanding at high elevations, and visitors should avoid stressful activities.
The Combined Array for Research in Millimeter-wave-Astronomy (CARMA). Photo Courtesy CARMA
The Combined Array for Research in Millimeter-wave Astronomy (CARMA) consists of six 10.4-meter, nine 6.1-meter, and eight 3.5-meter antennas that operate at millimeter wavelengths. The array sits at 7,200 feet (2,200m) at Cedar Flat in the mountains above the Caltech Owens Valley Radio Observatory. CARMA can observe radio emissions from the very early universe — primarily molecules, dust, and emissions from early galaxies, stars, and planetary systems around remote stars. Scientists also use it to observe planetary atmospheres, comets, and asteroids in our solar system. Because of its size, it achieves resolution below an arcsecond.
Thanks for the information, Peter! Stay tuned for more about the remote observatories Caltech astronomers employ as well as the research these scientists currently conduct with the various telescopes.