Theory Astronomers' Largest Tools and Sites

Professional astronomers, today, are operating either from the ground -through the various wavelengths available there- or from space, using dedicated space telescopes

Ground Telescopes Ground Radio Telescopes

Space Telescopes

Ground Telescopes

the Keck I and II telescopes at the summit of the Mauna Kea, Hawai

Refractors, after they had been improved by Chester Hall, a Englishman who deviced by 1733 a refractor which solved the question of the achromatism, a default plaguing any telecope glass lens, affixing a concave lens to a convex one, a limit was reached however as large lenses' weight brought to troubles. The Yerkes refractor, in the USA, at 1.02 meter by 1897 was the last large refractor. The Mount Wilson reflector, by 1917, at 2.5 meter of aperture, in the USA, heralded the era of large ground reflectors. Most of the ground telescopes the professional astronomers are using today are of the reflecting type and of the Ritchey-Chrétien type. The instruments, on the other hand, are remotely operated. No more nights in the dark and the cold in the prime focus cage of the giant reflectors, as the astronomers now work in a comfortable command room which is located just near their instrument. Astronomers nowadays can do almost all of their research on their laptops as they command the telescopes from computer screens. Some telescopes can also be operated remotely from laptops. Astronomers, on the other hand, mostly do not observe celestial objects with the eye but through varied sensors instead, optical or other

• the Mauna Kea site. It's on this summit of the Big Island, in Hawaii, USA, that the world's largest astronomical observatory is located. 13 telescopes are working near the summit of the Mauna Kea, at an altitude of 13,796 ft (4,205 m). The observatories, at the summit, are working in the optical, infrared, submillimeter and radio wavelengths. Of them, the famed Keck Observatory features the twin Keck telescopes. Both instruments are eight-story tall as they weigh 300 tons, with a 10-meter multi-celled mirror each. In the near and the mid-infrared, the Keck telescopes are using adaptive optics which compensate for the atmospheric distortions, and interferometery too, which combines the light from the both telescopes. The Keck I and II are operated by the Caltech (the famed 'California Institute of Technology', Calif.). The other institutions and countries operating at the Mauna Kea site are the University of Hawaii, the NASA, Canada, France, the United Kingdom, and Japan. The James Clerk Maxwell Telescope (JCMT) is the largest submillimeter telescope in the world, as the 8.2-meter, optical-infrared Subaru is operated by Japan. The Keck I and II are the world's largest telescopes. The 8.0-meter (26-ft) Gemini North Observatory is also located at the Mauna Kea site. a good start about the Mauna Kea observatories is at http://www.ifa.hawaii.edu/mko/maunakea.htm, via the University of Hawaii, Institute for Astronomy. The U.S. National Science Fundation (NSF) also is beginning to use since 2020, the 4-meter Daniel K. Inouye Solar Telescope on the neighbouring island of Maui, within the Haleakala Observatory
• the European Southern Observatory (ESO). With its two sites, at La Silla and Paranal, in Chile, the European Southern Observatory (ESO) is an intergovernmental European research organization, with 11 countries participating (Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Italy, Netherlands, Portugal, Spain, Sweden, Switzerland, United Kingdom). Its headquarters are in Garching, near Munich, Germany. The Paranal site, with the four 8.2-meter units and four auxiliary 1.8-meter mirrors which can be operated through interferometry into the Very Large Telescope Interferometer (VLTI), is the main site of the organization. The ensemble had been built in 1988. The four telescopes, working individually, are working in the visible and the infrared. They are named, in this case, the Very Large Telescope (VLT). The main mirrors of the VLT are engineered to withstand earthquakes, with clamps around the edges able to lift the entire mirror at a moment's notice, off its shape-maintaining actuators and secure it to the telescope's structure as the entire scope will swing. The ESO is considering to increase the power of the VLTI further as it projects to add it with telescopes which would be built on the surrounding summits and linked to the VLTI through an optical fiber. The resulting interferometer would thus have a virtual diameter of some miles! The K-band Multi-Object Spectrograph (KMOS) by late 2012 has been attached to the Very Large Telescope Unit Telescope 1. The ESO Paranal Observatory was added in late 2009 with the 18 British universities-funded VISTA, for 'Visible and Infrared Survey Telescope for Astronomy', a infrared telescope, the largest of its kind and used to study the nature and distribution of stars and galaxies or the underlying structure of the Universe. It will investigate too the dark matter and dark energy. The VLT Survey Telescope has been added to ESO by 2011 as it is the largest telescope worldwide working in the visible. The Next-Generation Transit Survey (NGTS) at the site since early 2014 is a wide-field observing system made up of an array of twelve telescopes, each with an aperture of 20 centimetres, and designed to operate in a robotic mode. The Paranal site is located 82 miles (130 km) south of Antofagasta, Chile, in the Atacama Desert, on the 8,600-ft (2,600-m) Cerro Paranal summit. The Cerro Paranal site is treated with 350 nights per year with fine observation conditions. The La Silla site is harboring middle-sized instruments mainly, of the order of 2 meters in diameter. It's located at the southern extremity of the Atacama Desert, 100 miles (160 km) North of La Serena, Chile. for more see at the European Southern Observatory

->A New, Spanish 10-Meter Telescope!
The 'Gran Telescopio de Canarias' or 'GTC', with a diameter of 10,4 ( ft) and with its mirror made of 36 hexagonal segments, opened lately in the island of La Palma in Canarias, a possession of Spain. The telescope is managed by Grantecan, a Spanish public agency as its official inauguration is to take place by next July 2009

• the Instruments of the National Optical Astronomy Observatory (NOAO). The National Optical Astronomy Observatory (NOAO) is the acting managing institution for the AURA (the 'Association of Universities for Research in Astronomy'), a consortium of 32 universities and educational and other non-profit institutions, operating world-class astronomical observatories. The NOAO is funded by the National Science Fundation (NSF), the US federal agency responsible for the progress of science and the funding source for 20 percent of all federally supported, colleges and universities searches in the United States. The NOAO is headquartered in Tucson, Arizona. The NOAO is responsible for the Kitt Peak National Observatory, this observatory located in the Sonora Desert, on the Kitt Peak Mountain, 55 miles (90 km) southwest of Tucson. It holds more than 20 telescopes, of them the Mayall 4-meter. The Kitt Peak Mountain is home too to the National Solar Observatory (NSO), with the famed McMath-Pierce Solar Telescope (the NSO manages too another facility at the Sacramento Peak). The NOAO, further, is managing the Cerro Tololo Inter-American Observatory, located in northern Chile. A 4-meter telescope, among others, is found there. The NOAO, at last, is the U.S. astronomical community representative to the joint, multinational International Gemini Project. This project comprises two twin 8.1-meter telescopes, one at the Mauna Kea, the other near the Cerro Tololo. Such both locations introduce to studies of the northern and the southern hemispheres sky. The telescopes are integrated with modern networking technologies. Their headquarters are found in Hilo, Hawaii and La Serena, Chile. for more see the NOAO site
• the Lick Observatory is a multi-campus research unit of the University of California. It is located atop the 4,200-ft (1,400-m) Mount Hamilton, which is found in the Diablo Range, east of San Jose, California. Due to an effective counter-light-pollution program, the Lick Observatory, although located near urban centers, is still able to perform an important astronomical work. The Adaptive Optics/Laser Guide Star Program is another aspect of how the Lick Observatory works. This program allows the Shane 3-meter reflector to compensate for the effects of atmospheric turbulences through a deformable mirror. The Lick Observatory is home, too, to the ancient, 36-inch Lick Refractor. for more see at University of California Observatories/Lick Observatory
• the Palomar Observatory, on the 5,600-ft (1,800-m) Palomar Moutain, 100 miles (160 km) southeast of Pasadena, Calif. had its history beginning in 1930 when a new site was searched by George E. Hale, an American astronomer, in the name of the Caltech (the 'California Institute of Technology') for a 200-inch (5-meter) telescope, which was funded by the Rockfeller Foundation. The telescope eventually became operational in 1949, as its name had been changed meanwhile to the 'Hale Telescope'. The 200-inch telescope was the world's largest telescope between 1948 and 1993. This telescope was instrumental to the development of the Big Bang theory. The 200-inch Hale Telescope of the Mount Palomar is still an astronomical workhorse today, which is used at the Palomar observatory along with other famed telescopes, like the 18-inch and 48-inch Schmidt Camera telescopes. for more see at the Palomar Observatory site
• the Big Bear Solar Observatory (BBSO) is managed by the New Jersey Institute of Technology for a univesity consortium. It is located 100 miles East of Pasadena, California, in the middle of Big Bear Lake, at an elevation of 6,700 ft (2,200 m). It's the main location in the world for the observation of the Sun. for more see at the BBSO, Big Bear Solar Observatory

->Next Generation Ground Telescopes
Astronomers, worldwide, are aiming to build the next generation ground telescopes, in the order of the 100 ft (30 meters) of diameter, which will allow to push further to the beginnings of the Universe, by about 13 billion years. An example of that is the joined project by the University of California, the Caltech and the Association of Canadian Universities for Research in Astronomy, in Hawaii where the Mauna Kea summit has been chosen in 2009 instead of the Cerro Amazones for the 'Thirty Meters Telescope' (TMT), Chile like the site for their telescope. Europe, or Russia, too have such projects with the European ESO 39.3-meter, advanced active and adpatative optics European Extremely Large Telescope, or E-ELT to be operational by 2024 from atop Cerro Amazones, in the Atacama Desert, Chileas the first stone of which was been laid down by May 2017

Ground Radio Telescopes

antennas of the VLA, Socorro, New Mexico. picture NRAO

Radio astronomy is the branch of astronomy which works in the radio range as it studies the radio waves emanating from the celestial objects, from the black holes at the center of the galaxies to the Sun or the interstellar gas clouds. Radio astronomy started in the 1930s only. Scientists first detected radio waves coming from an astronomical object -- our Milky Way -- in 1932. Following this discovery, radio astronomy developed into its own specialized science field and astronomers around the world beginnning to look into space for something other than visible light, with something other than just optical telescopes. Radio astronomy is working in the wavelengths of about 10 meters (30 MHz) and 1 millimeter (300 GHz). Radio astronomy was born at frequencies below 100 megahertz and developed from there. It helped pave the way for modern astronomy as one of the most important contributions in radio astronomy was by a young graduate student at New Hall (since renamed Murray Edwards College) of the University of Cambridge, U.K. Jocelyn Bell, who discovered the first hints of radio pulsars in 1967. Radio-telescopes, just like their optical counterparts, may work on the principle of interferometry, combining their strength to yield high-resolution virtual receivers. Such radio facilities, on the other hand, may be networked, worlwide, producing higher resolution still

• the National Radio Astronomy Observatory (NRAO) facilities. The NRAO is an institution of the National Science Foundation (NSF), this US federal agency responsible for the scientific research in the USA. The NRAO is operated under coooperative agreement by Associated Universities, Inc., a group of the northeastern universities, founded in 1946. The NRAO is managing 5 major radio astronomy facilities: the Karl G. Jansky Very Large Array (VLA), an ensemble of 27 82-foot (25-m) antenna gathered into a Y-shaped configuration 50 miles West of Socorro, New Mexico. In its widest configuration the Y shape may attain 26 miles (42 km) in length. The Very Long Baseline Array (VLBA), on the other hand, is a worldwide system of 10 82-foot (25-m) radio-telescope antennas, mostly spreaded in the continental USA (with one at the Mauna Kea, Hawaii). Antennas are found, for example,in Kitt Peak, Arizona, Owens Valley, California, or Hancock, New Hampshire. The NRAO, at last, is managing the Green Bank Telescope (GBT), the world's largest fully steerable radio-telescope, located in Green Bank, Pocahontas County, West Virginia. This antenna is 100-meter wide. for more, see at the National Radio Astronomy Observatory site
• the Atacama Large Millimeter Array (ALMA) is an international, ESO (European Southern Observatory)-USA-Canada project, inaugurated in March 2013, with 66 39-foot (12-m) antennas located in Llano de Chajnantor, Chile, in the Atacama Desert. It can be configured in different ways, with dimensions ranging from 500 ft (150 m) to 10 miles (16 km). The Expanded Very Large Array (EVLA) Project, at last, is building upon the net of antennas of the VLBA, expecting to add 8 more antennas to the network. The ALMA correlator, a computer system, has over 134 million processors and performs up to 17 quadrillion operations per second, a speed comparable to the fastest general-purpose supercomputer in operation today. The correlator continually combines and compares faint celestial signals received by the antennas in the ALMA array, which are separated by up to 16 kilometres, enabling the antennas to work together as a single, enormous telescope. The ALMA works in the millimeter and sub-millimeter radio waves, or the cold objects in the Universe
• also in the Atacama Desert, the submillimeter largest world telescope should become operational beginning by 2012, as a joint Europe, Japan, USA and Chili project

Space Telescopes

the Hubble Space Telescope as seen in orbit. picture NASA

NASA currently has three major space telescopes, or NASA 'Great Observatories,' orbiting in space: the Hubble Space Telescope, the Chandra X-Ray Observatory, and the Spitzer Space Telescope. Those space telescopes allow for the observation of the Universe at various wavelengths. Another NASA space observatory was the Compton Gamma Ray Observatory, which was working in the gamma rays. It has already been de-orbited. In anticipation of the Hubble launch, NASA set up the Great Observatories program to fly a total of four space telescopes designed to cover a range of wavelengths: Hubble, Spitzer, the Chandra X-ray Observatory and the Compton Gamma Ray Observatory. All NASA space telescope were the most productive science facilities ever built as all were all top recommendations of a U.S. National Academy of Sciences' 'Decadal Survey for Astronomy and Astrophysics.' NASA's Marshall Space Flight Center played a significant role in NASA’s Great Observatories, especially in managing the development of the Hubble Space Telescope and in managing the development, flight and current operations of Chandra

• the Hubble Space Telescope. Advocated by astrophysicist Lyman Spitzer about 1970 -- the Hubble space telescope technically is of the Ritchey-Chrétien type -- the Hubble Space Telescope began to be built in 1981 in Baltimore, Maryland. The telescope was eventually released into orbit on April 24th 1990 by the Space Shuttle STS-31 mission, with shuttle Discovery for a 10 to 15 year-mission, and turning the first of NASA's Great Observatories to reach orbit. The telescope's diameter is of 94 inches (240 centimeters) as it is orbiting on a circular low-Earth orbit of about 350 miles altitude at a speed of 17,500 mph. After that a grave optical defect was discovered in the telescope's primary mirror, and that COSTAR, a complex packaging of mirror pairs to rectify that was installed in 1993, the Hubble Space Telescope is still able to work. Not only was Hubble, when launched, returning blurry images, a flaw called spherical aberration, but it was also having trouble locking onto guide stars guides It's working in the visible and the infrared. The Hubble was designed with on-orbit servicing missions in mind as a way of extending the telescope’s lifespan. Three servicing mission by the Space Shuttle, in 1997, 1999, and 2002, provided Hubble with new instruments, replacement parts, and maintenance. The Hubble Space Telescope is a joint ESA (European Space Agency)/NASA (Goddard Space Flight Center, GSFC) project. The Space Telescope Science Institute (STScI) conducts Hubble science operations from Baltimore, as the institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., Washington, D.C. Hubble is orbiting in a Low Earth Orbit (LEO), at about 375 miles (600 km) above the surface of the Earth. Such an altitude allows the telescope to escape the distorting effects of the Earth's atmosphere as it permits however for servicing missions. Hubble is completing an orbit every 97 minutes. Along 25 years, the Hubble had made more the 1 million observations, observing 38,000 celestial targets, representing more than 100 To of data as 4,000 astronomers from all over the world have used the telescope and yielding more than 11,000 scientific papers, making it one of the most productive scientific instruments ever built. The Hubble can now reach to 500 to 600 million years after the Big Bang, as it is observing primarily in the visible light and ultraviolet wavelengths, with some infrared vision too, using a Cassegrain-type telescope with 2 photographic chambers at the focus -one with a high resolution and another for weak objects, 2 spectrographs -remark idem- and 1 ultrarapid photometer and observing the Universe 24 hours a day, 365 days a year. The Hubble Space Telescope performs one orbit about the Earth in 96 minutes, as it has a total mass of 11.3 tons, a length of 44ft and a diameter of 14 ft. After a cancellation in 2003, a NASA decision by 2006 allowed to a last repair mission in 2008 which eventually launched by May 2009. It switched the Wide Field and Planetary Camera 2 out for a more advanced camera, the Wide Field Camera 3, which would capture starry images at a far greater resolution and allowed to its best performance during some 5 or 7 years. The Hubble also was fitted with with the Cosmic Origins spectrograph, allowing in the ultraviolet light. Since, the Hubble Space Telescope made over 1.4 million observations. The Hubble Space Telescope is a joint mission between NASA and the European Space Agency (ESA) as the telescope is operated from the Goddard Space Flight Center in Greenbelt, Maryland. see more at the Hubble's site
• the Chandra X-Ray Observatory was deployed in space in July 1999, by the Space Shuttle STS-93 mission. It's was the most sophisticated X-ray observatory built to that date. Chandra is working in the X-rays as it studies the high-energy regions of our Universe. It's Chandra which is providing with those now famed pictures of supernovae remnants or of gas clouds in galaxies clusters. The telescope was named the Chandra X-ray Observatory in honor of the late Indian-American Nobel laureate, astrophysicist Subrahmanyan Chandrasekhar. The Chandra X-Ray Observatory is on a highly elliptical orbit. It's getting distant from the Earth up to 86,500 miles (139,000 km) away allowing for long observations unobscured by Earth's shadow. Originally called the Advanced X-ray Astrophysics Facility (AXAF), the telescope was first proposed to NASA in 1976. 'Chandra' means 'Moon' or 'luminous' in Sanskrit. see more at the Chandra site
• the Spitzer Space Telescope. The Space Infrared Space Infrared Telescope Facility (SIRTF), is studying the Universe in the infrared. Water vapor prevents a large section of the infrared spectrum from reaching ground-based observatories. The telescope was renamed the "Spitzer Space Telescope" in honor to Dr. Lyman Spitzer Jr. who worked at Princeton University for 50 years and was the first to propose, in 1946, to put telescopes into orbit. The Spitzer Space Telescope is coming like a complement to the Hubble Space Telescope, which works in the visible light, and the Chandra X-ray Observatory, which works is the X-rays. The Spitzer Space Telescope launched in August 2003. To avoid the warmth of the Earth, it's trailing behind it, on the orbit. The distance to the Earth will lengthen by 0.1 AU a year. The telescope is operated by the JPL for NASA. see more at the Spitzer Space Telescope site
• the Solar and Heliospheric Observatory (SOHO) is not, so to speak, a space telescope. It's better a space mission. Its contribution to the daily study of the solar activity however allows to award it its place on this page. SOHO is a cooperative ESA (European Space Agency)/NASA mission which was launched in December 1995. Soho is orbiting at the Lagrangian point L1, between the Earth and the Sun. It provided from there an uninterrupted series of data about the solar activity as seen in various wavelengths. Such data are of importance as the "solar weather" may affect the satellites in orbit around the Earth. Since June 2003, the aging satellite has had its high gain antenna parked, as the craft is rotated now each half-orbit to keep it Earth-directed. This brings to some "blackout" periods about every 3 months. NASA Heliophysics System Observatory, on the other is a concept comprised of numerous instruments on multiple observatories, like SOHO, Japanese Hinode mission as managed by NASA Marshall center, or the recentest SDO, allowing for more detailed views of our star, along with Earth-based observatories
• NASA's SOFIA observatory is a heavily modified Boeing 747 Special Performance jetliner that flies at altitudes between 39,000 to 45,000 feet (12 to 14 km) and serves like a observatory in the infrared. A 20-person crew is controlling the largest airborne telescope to date, at 106" in diameter. SOFIA is a joint project of NASA and the German Aerospace Center (DLR). NASA's Armstrong Flight Research Center manages the program, and the observatory is based at the center's Science and Aircraft Integration Facility in Palmdale, Calif. NASA Ames Research Center at Moffett Field, Calif., manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Md., and the German SOFIA Institute (DSI) at the University of Stuttgart (NASA paved the way for airborne astronomy in 1965 by flying a modified Convair 990 aircraft to study a solar eclipse from inside the path of totality. In 1968, astronomers used 12-inch telescopes in the cabins of Learjet aircraft to study objects like Venus using infrared light. That then led to the development of NASA's Kuiper Airborne Observatory, or KAO, a converted C-141 cargo aircraft that carried a 36-inch reflecting telescope operating from 1975 to 1995. Since then, those roles passed to the SOFIA)

->The JWSP, the Successor to Hubble!
Scheduled to launch now in 2018, the 'James Webb Space Telescope' (JWSP) is the next generation space telescope which will allow astronomers to get further towards the Dark Ages of the Universe. It will be observing in the far visible to the mid-infrared part of the spectrum with a mirror twice the one of Hubble and made of the combination of 18 mirrors. Northrop Grumman Space Technology is the prime contractor to develop the JWST as Goddard Space Flight Center is managing the project and the Space Telescope Science Institute will be responsible for the telescope science and mission operations -as it is too now for the Hubble. ESA and the Canadian Space Agency too are part of the project. By June 2012, two former spy satellite telescopes were given to NASA by the National Reconnaissance Office (NRO), the U.S. spy satellite agency and should be repurposed by NASA for astronomical research. Main mirror of both telescopesis at 8 feet wide as they could be part in a next future of the solutions of replacement for the aging Hubble Space Telescope

Some shorter-lived space missions regularly launch to the terrestrial orbit for dedicated missions, like the Galex mission which is studying the galaxies in the ultraviolet, or the Swift craft which is dedicated to the gamma-rays bursts. Such missions are launched by NASA or by other space agencies. for more about such missions, see our page "Missions"