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AURA Gemini South Telescope in Chile
The TELESCOPE is 400 years old.
Hans Lippershey, also known as Jan or Hans Lippersheim, was a maker of eyeglasses, or spectacles, in the Netherlands, when he invented the "looker" in 1608.
Not all historians agree that Lippershey was the first to build a telescope, but one story tells of two children playing with lenses in his shop. They told him a weather vane on a church seemed larger when peered at through two lenses. He placed a tube between the lenses, and made what today we call a telescope.
Kijker. When Lippershey announced his invention on October 2, 1608, he called it a kijker, which means looker in Dutch.
Whether or not his looker was the first, Lippershey seems to have been the first person to describe a telescope in writing. That alone became important when the news reached Italian stargazer Galileo Galilei, who then built his own telescope and used it to revolutionize the study of extraterrestrial bodies.
Transformation. Lippershey's looker changed everything for astronomers who previously had lacked reliable tools to observe faraway stars or even the planets in our Solar System.
Before Lippershey and Galileo, magnification instruments had not been used to investigate objects beyond Earth. Since their time, far more powerful visible-light telescopes have been developed along with other types of telescopes capable of "seeing" invisible forms of radiation, such as infrared, ultraviolet, radio, X-ray, and gamma-ray.
Optical telescopes 400 years later, as represented by the Hubble Space Telescope, are 100 million times more sensitive than Galileo's telescope.
Even so, while today's visible-light telescopes are far more powerful and adaptable, the underlying blueprint has remained the same since 1608.
What is a telescope? A telescope is a device used by an astronomer to magnify images of distant objects. It makes faraway things seem nearby.
A telescope extends human vision by making distant things appear larger, sharper and brighter. Some telescopes can be used to record images of objects not seen by the human eye.
Telescopes have been improved by later inventions – the camera, computer, spectrograph, charge-coupled device, rocket, and satellite.
Telescopes as tools. Telescopes are the main tools used by amateur and professional astronomers to explore the Universe. The way a telescope works depends on what an astronomer wants to look for across deep space.
For most people, a telescope is an optical device, which lets an astronomer see objects in space that radiate or reflect visible light. However, much of what can be seen across the Universe is invisible to human eyes because we see only the visible light portion of the electromagnetic spectrum.
Seeing other wavelengths. While the first optical telescope was created 400 years ago, the other kinds of telescopes were invented in the 20th century.
Since the 1960s, telescopes sent up to orbit Earth have allowed astronomers to observe a wider portion of the electromagnetic spectrum.
Stars, black holes, pulsars, quasars, galaxies and other objects strewn across deep space emit lots of energy across the electromagnetic spectrum. Astronomers use radio, infrared, ultraviolet, X-ray and gamma-ray telescopes to look at those invisible emissions to gain a better understanding of the Universe.
MORE ABOUT THE ELECTROMAGNETIC SPECTRUM »»
Types of Astronomy
Each kind of astronomy needs its own telescope to tune in a different wavelength of energy along the electromagnetic spectrum. Many celestial phenomena can be seen at more than one wavelength.
- Optical astronomy began with Lippershey's "looker" in 1608. Optical telescopes can be used on Earth and in space.
- In 1989, the European Space Agency (ESA) sent the The Hipparcos Space Astrometry Mission to orbit. Hipparcos was assigned to measure precisely the position and motion of 120,000 stars. It also was to record the properties of 400,000 more stars in a project known as Tycho. It mapped until 1983 and a catalog of its work was published in 1997.
- In 1990, NASA launched the Hubble Space Telescope (HST), as the first in NASA's series of Great Observatories in Space. Hubble is an example of a huge optical telescope mounted in an orbiting satellite through which astronomers look out across the Universe without the distortion of light by the Earth's atmosphere. Hubble not only observes in visible light, but also in infrared and ultraviolet.
Someday, there may be a large optical telescope on the far side of the Moon where's Earth's light pollution would not interfere.
MORE ABOUT THE HUBBLE SPACE TELESCOPE »»
HUBBLE SEES STARS LIKE GRAINS OF SAND ON A BEACH »»
THE WORLD'S LARGEST OPTICAL TELESCOPES »»
- Radio astronomy had to wait until the 1930s because, before then, astronomers could observe only the visible wavelengths. Then, two Americans opened a window on radio waves traveling across the Universe.
- In 1931, Karl Jansky was looking for the cause of static on his radio when he figured out how to tune in radio waves coming from somewhere in the sky. He founded radio-astronomy when he detected radio waves coming from the center of our Milky Way galaxy.
- In 1937, Grote Reber invented the radiotelescope when he built a 31-ft. dish antenna in his backyard and used it to pinpoint the first radio sources beyond Earth. He mapped the spread of natural radio signals across the Milky Way.
Radiotelescopes also can be used on Earth or in space. Radiotelescopes were used to discover strong natural radio signals from Jupiter and to measure the temperatures of all the planets in our Solar System. A radiotelescope is composed of a radio receiver and an antenna. Because the natural radio signals received from some objects faraway across deep space are extremely faint when they arrive at Earth, raditelescopes are large. They require the most sensitive radio receivers. The first large, fully-steerable radiotelescope was turned on in 1957 at Jodrell Bank, England. The world's largest fully-steerable radiotelescope is the 328-ft. (100m) antenna at Germany's Max Planck Institute for Radio Astronomy. The largest single radiotelescope in the world is the 1,000-ft fixed antenna at the Arecibo Observatory in Puerto Rico. The Very Large Array of 27 antennas sprawls across New Mexico. Radio signals received from deep space by the VLA are combined electronically to create a virtual antenna 22 miles across.
MORE ABOUT THE VERY LARGE ARRAY »»
NATIONAL RADIOASTRONOMY OBSERVATORY IMAGES »»
- Infrared astronomy dates from 1800 when English astronomer William Herschel, in a fortunate accident, found infrared radiation in sunlight. He was using a prism to split sunlight into the spectrum of colors and placing a thermometer in each color. He noticed a thermometer just outside the red end of the spectrum, where there seemed to be no light, registered the highest temperature. Herschel called the invisible light infrared, which meant beneath red.
- In the 1920s, American astronomers Seth Nicholson and Edison Pettit observed celestial objects in infrared.
- In 1931, Kodak made photographic film sensitive to infrared light.
- In the 1940's, Philo Farnsworth invented the infrared telescope during World War 2.
- In the 1950s, new technology fostered modern infrared astronomy.
- From the 1980's, infrared telescopes have been sent to orbit above Earth.
Infrared telescopes are affected by Earth's atmosphere. They have to be at high altitudes, above water vapor in the atmosphere, or else out in space. Frequently they are on mountaintops. The large Spitzer Infrared Telescope Facility, formerly known as the Space Infrared Telescope Facility (SIRTF), was launched in 2003. It became NASA's fourth Great Observatory in Space. The Hubble Space Telescope also sees infrared light.
MORE ABOUT THE SPITZER INFRARED TELESCOPE »»
COLLECTION OF SPITZER INFRARED IMAGES »»
INFRARED ASTRONOMY TUTORIAL »»
- Ultraviolet astronomy followed the discovery of ultraviolet light in 1801 by doctor and pharmacist Johann Wilhelm Ritter in Silesia, now part of Poland. His discovery came just one year after William Herschel had discovered infrared light. When Ritter heard of Herschel's discovery of invisible light in the spectrum beyond visible red light, he decided to look for invisible light beyond the violet end of the visible light spectrum. Sure enough, something beyond the blue end of the visible spectrum changed the color of his silver chloride chemical to black. Ritter called the ultraviolet, above violet, radiation he had found chemical rays.
- In 1966, ultraviolet astronomy pioneer George Carruthers of the U.S. Naval Research Laboratory sent his ultraviolet camera aloft on sounding rockets.
- In 1970, Carruthers detected molecular hydrogen in deep space during a flight of his instrument.
- In 1972, Carruthers' Far Electrograph Ultraviolet Camera flew to the Moon aboard Apollo 16. Previously unseen features of Earth's far outer atmosphere, as well as stars, nebulas and galaxies, turned up in the camera's ultraviolet images from the lunar surface.
- From the 1980s, a series of satellite observatories have been sent to Earth orbit – the International Ultraviolet Explorer (IUE), Extreme Ultraviolet Explorer (EUVE), and Hubble Space Telescope (HST).
- In 1990, astronomers aboard space shuttle Columbia used the ultraviolet and X-ray telescopes of the ASTRO space shuttle observatory to study quasars, pulsars, black holes, galaxies, and high-energy stars.
- In 1999, NASA launched the Far Ultraviolet Spectroscopic Explorer (FUSE) as part of its Origins program.
Ultraviolet is a form of light with higher energy than visible light, but without as much energy as X-rays. Some of the hottest and most energetic stars can be seen in ultraviolet light. However, ultraviolet light arriving at Earth is mostly blocked by our planet's atmosphere and so can be studied well only from space.
In fact, ultraviolet telescopes have to work at altitudes even higher than infrared telescopes. In the stratosphere 12-24 miles above the surface, Earth's ozone layer blocks most ultraviolet (UV) light. Because the atmosphere absorbs UV, life on the surface of our planet is protected from its damaging effects. However, the ozone layer shield means some of the hottest and most energetic stars across the Universe can only be studied through space telescopes.
HOPKINS ULTRAVIOLET TELESCOPE (HUT) ASTRO »»
HUBBLE ULTRAVIOLET VIEWS OF NEARBY GALAXIES »»
- X-ray astronomy followed the discovery of X-rays by German physicist Wilhelm Roentgen in 1895. His mysterious "X-radiation" was able to pass right through many materials that absorb visible light. Natural X-rays from across deep space are very high energy so it's fortunate Earth's atmosphere shields us. However, that means X-ray telescopes must be above the atmosphere to see distant objects emitting X-rays.
- In 1949, a set of small Geiger counters sent aloft on a captured German V-2 rocket, by a research team led by Herbert Friedman of the U.S. Naval Research Laboratory, detected weak X-rays coming from the hot outer layers of the Sun's atmosphere, the solar corona.
- In 1962, Riccardo Giacconi at American Science and Engineering in Cambridge, Massachusetts, and a team of scientists sent up an improved detector on an Aerobee rocket. It saw Scorpius X-1, the first known source of X-rays outside our Solar System.
- In 1963, Giacconi and his team made the first imaging X-ray telescope and sent it aloft on a small sounding rocket. The telescope recorded crude images of hot spots in the upper atmosphere of the Sun. Interestingly, the body of Giacconi's telescope was about the same length and diameter as the optical telescope built by Galileo in 1610.
- In 1970, NASA's first X-ray telescope was the satellite Uhuru — Swahili for freedom — launched from the African nation of Kenya. Also known as the Small Astronomical Satellite 1 (SAS-1), it was the first earth-orbiting mission dedicated entirely to celestial X-ray astronomy. It worked until 1973.
- In 1977, NASA launched the first of a series of very large scientific payloads called High Energy Astronomy Observatories(HEAO). The first, HEAO-1 surveyed the X-ray sky almost three times. It worked until 1979.
- In 1983, the European Space Agency's X-ray Observatory (EXOSAT) began observing X-ray binary stars, variable stars, white dwarf stars, clusters of galaxies, and supernovas. It discovered oscillations in X-ray pulsars. The satellite worked until 1986.
- In 1978, NASA orbited the the first fully imaging X-ray telescope. It was the second of NASA's High Energy Astrophysical Observatories (HEAO-2). Renamed Einstein after launch, the satellite worked until 1981.
- In 1990, astronomers aboard space shuttle Columbia used the the Broad Band X-ray Telescope (BBXRT), part of the ASTRO space shuttle observatory.
- In 1990, NASA orbited the ROentgen SATellite (ROSAT), an X-ray observatory, designed and operated by Germany and Great Britain. The satellite was turned off in 1999.
- In 1991, Japan launched a satellite named Yohkoh, or "sunbeam," to study X-rays and gamma rays from the Sun. The spacecraft was built in Japan with telescopes from the U.S. and Great Britain. It worked until 2001.
- In 1995, NASA launched the Rossi X-ray Timing Explorer (RXTE) satellite.
- In 1999, the large Chandra X-ray Observatory was launched to become NASA's third Great Observatory in Space.
- In 1999, the European Space Agency (ESA) launched the X-ray Multimirror Mission (XMM) space.
- In 2002, ESA launched the International Gamma-Ray Astrophysics Laboratory (INTEGRAL).
Those pioneering X-ray astronomers in the 1960s were surprised when their Geiger counters sent aloft on high-altitude rockets revealed high-energy X-rays streaming away from many objects across the Universe. Today, only four decades after Giacconi's 1963 instrument, X-ray telescopes that can focus X-rays, as represented by the Chandra X-ray Observatory, are 100 million times more sensitive.
More than 100,000 X-ray sources have been detected across the Universe. The most distant object seen in X-rays is 13 billion lightyears from Earth.
MORE ABOUT THE CHANDRA X-RAY OBSERVATORY »»
IMAGINE THE UNIVERSE IN X-RAYS »»
CHANDRA X-RAY OBSERVATORY PHOTO ALBUM »»
MILESTONES IN X-RAY ASTRONOMY »»
- Gamma-ray astronomy had to await the time when it became possible to get detectors above most of Earth's atmosphere. Scientific research from 1948 to 1958 led astronomers to believe that processes occurring in objects across the Universe – supernova explosions, cosmic ray interactions with interstellar gas, and interactions of energetic electrons with magnetic fields – could result in the emission of gamma rays. Then, it was only in the 1960s that they were able to detect gamma rays. Gamma-rays from deep space are mostly absorbed by Earth's atmosphere, so detectors had to be carried up near space on balloons or to space aboard satellites. Telescopes that see gamma rays reveal how violent the Universe can be. They bring new views of pulsars, black holes and binary stars. In fact, black holes and other dense stars radiate more energy in gamma rays than in visible light. Recent gamma ray observations have uncovered frequent explosions of stars in our own Milky Way galaxy.
- In 1961, the first gamma-ray telescope, Explorer XI, was lauched.
- In 1972, the first spacecraft dedicated to gamma rays was SAS-2, the second Small Astronomy Satellite.
- In 1975, the European Space Agency launched the gamma-ray satellite, COS-B.
- In 1991, the large Compton Gamma Ray Observatory was launched aboard shuttle Atlantis to become NASA's second Great Observatory in Space. At 17 tons, CGRO was the heaviest astrophysical payload ever flown at the time. The observatory satellite was de-orbited in 2000.
Gamma rays are the highest energy, shortest wavelength radiation on the electromagnetic spectrum. Gamma-rays have more than 10,000 times more energy than visible light. Fortunately, Earth's atmosphere protects life on the surface from gamma rays. Gamma-ray bursts lasting from a fraction of a second to many minutes have been detected coming from space. It's not clear what causes them, but they seem to originate in sources very far away.
MORE ABOUT THE COMPTON GAMMA RAY OBSERVATORY »»
COMPTON GAMMA RAY OBSERVATORY IMAGE GALLERY »»
THE VARIETY OF TELESCOPES »»
The Next Generation
There are scores of large telescopes already based on Earth. However, even-larger telescopes on Earth are planned and under construction at such disparate locations as Arizona, British Columbia, California, Canary Islands, Chile, China, Greece, Hawaii, Ireland, South Africa and Wisconsin.
PLANNED TELESCOPES ON EARTH »»There's a lot to see at all wavelengths and, so far, much of it remains to be explored. Telescopes positioned on the surface of Earth are unable to observe many portions of the spectrum because much of the energy coming to us from across the Universe is blocked by our planet's outer atmosphere or else absorbed by moisture in the atmosphere before it can reach the ground. To overcome that problem, telescopes are based in space.
- Very Large Telescope. The European Southern Observatory's Very Large Telescope (VLT) at the Paranal Observatory at Atacama, Chile, currently is the world's largest and most advanced optical telescope.
The VLT is composed of four 8.2-meter (323 in.) reflecting telescopes accompanied by several smaller, moving 1.8-meter (71 in.) auxiliary telescopes. Light waves received from deep space by all of these telescopes atop Paranal mountain are combined in the VLT's interferometer (VLTI) to create far greater resolution than any one alone could achieve. With its extraordinary optical resolution and vast surface area, the VLT produces extremely sharp images. It can record light from the farthest and faintest objects across the Universe.
Paranal Observatory is atop 8,645-ft. Cerro Paranal (Paranal Hill) in the Atacama Desert in northern Chile, arguably the driest area on Earth. The mountain is 75 miles south of the town of Antofagasta and just seven miles from the Pacific Coast. The Paranal mountain was chosen for its excellent atmospheric conditions and its remoteness ensuring that observations undisturbed by dust and light from roads and mines, and other human activities.
The four large telescopes are named Antu, Kueyen, Melipal and Yepun after sky object names in the Mapuche (Mapudungun) language of indigenous people who live in the the Bio-Bio river valley 300 miles south of Santiago de Chile. Antu (telescope UT1) is the Sun, Kueyen (UT2) is the Moon, Melipal (UT3) is the Southern Cross, and Yepun (UT4) is the evening star Venus.
THE VERY LARGE TELESCOPE »»
PARANAL OBSERVATORY »»
TOP 20 IMAGES FROM THE VLT
Dozens of telescopes also have been launched to space in recent decades. Many more are planned with names such as Agile, ARISE, COBRAS, Constellation X, Darwin, EXIST, ExNPS, GAIA, Generation-X, Herschel, HSIM, IRIS, Kepler, LISA, MAXIM, Pathfinder, Planck, RadioAstron, SAMBA, SIM, Spectrum, StarLight, Swift, SXG, TPF and Webb.
PLANNED TELESCOPES IN SPACE »»
The expanse of wavelengths across the full electromagnetic spectrum is considerably wider than the narrow rainbow of colors seen by the human eye. Astronomers need telescopes that can receive the entire range of frequencies so they can observe the Universe of objects radiating energy across the extent of the spectrum.
For instance, much of the Universe consists of gas and dust that is far too cold to radiate in visible light or at shorter wavelengths such as X-rays. However, even at temperatures far below the most frigid spot on Earth, the gas and dust in deep space can release energy at far-infrared and submillimeter wavelengths. Sometimes stars and other bodies are hot enough to shine at optical wavelengths that we might be able to see, but they are hidden from our view behind enormous clouds of dust that absorb the visible light. Fortunately, the dust clouds re-radiate the absorbed energy at the far-infrared and submillimeter wavelengths.High energy astrophysics is a young discipline, whose history is only a few decades old, and requires space-borne instruments to observe the X-ray and gamma-ray sky.
- The Gamma-ray Large Area Space Telescope. NASA launched GLAST to be a window on the universe through which scientists will study gamma rays, the highest-energy form of light.
GLAST will search out super-massive black holes, merging neutron stars, hot gas streaming at the speed of light, and other high-energy objects across the Universe. It will explore the high-energy elements of the Universe in search of answers to many questions about deep space objects.
Astronomers will use GLAST to study how black holes can accelerate jets of gas outward at high speeds. Physicists will use the telescope to study subatomic particles at energies far greater than those seen in particle accelerators on Earth. Cosmologists will use it to study the birth and early evolution of the Universe.
GLAST's mission is to explore the most extreme environments in the Universe, where nature harnesses energies far beyond anything possible on Earth, search for signs of new laws of physics and what composes the mysterious Dark Matter, explain how black holes accelerate immense jets of material to nearly light speed, help crack the mysteries of the stupendously powerful explosions known as gamma-ray bursts, and answer long-standing questions across a broad range of topics, including solar flares, pulsars and the origin of cosmic rays.
GLAST was launched June 11, 2008, from Cape Canaveral Air Force Station in Florida. Working with NASA are the U.S. Department of Energy and institutions in France, Germany, Japan, Italy and Sweden.
Earth's night sky that we see in visible light may appear placid, peaceful and even unchanging. However, the Universe, when seen in gamma-rays, is a place of chaotic violence. Gamma-ray bursts are brief but tremendously intense explosions faraway in deep space. There is nothing more powerful in the Universe.
No one is sure what causes gamma-ray bursts. Such powerful energy might result from the collision of two neutron stars. It might happen when when an extreme supernova would result from the final death explosion of an extremely massive star.
Whatever they are, gamma-ray bursts occur in galaxies very far away. The distances away from us is so great it astronomers describe it as cosmological, or beyond ordinary comprehension. Astronomers use gamma-ray telescopes to see those outbursts.
NASA GLAST »» Stanford GLAST »»
- Herschel Space Observatory. Scheduled for launch at the end of 2008, the European Space Agency's Herschel telescope will be positioned in space to study the Universe in light from the far-infrared and submillimeter portions of the electromagnetic spectrum. During its three years service in orbit, the Herschel should reveal the oldest and most distant stars and galaxies. It also will be able to look closer to home at planets, moons and other bodies in our own Solar System.
Ten countries are participating in Herschel, which is the fourth Cornerstone mission in the ESA's Horizon 2000 program. Originally known as the Far InfraRed and Submillimetre Telescope (FIRST), the spacecraft was renamed for Great Britain's William Herschel, who discovered in 1800 that the spectrum extends beyond visible light into infrared.
Herschel has the largest mirror ever built for a space telescope. When launched, with a primary mirror 3.5 meters in diameter, Herschel will become the largest infrared telescope ever sent to space. Its three instruments are known as HIFI, SPIRE, and PACS.
Herschel will collect long-wavelength radiation from some of the coldest and most distant objects in the Universe. In addition, Herschel will be the only space observatory to cover a spectral range from the far infrared to sub-millimetre. It will observe at some wavelengths that never have been explored.
After a four-month journey from Earth, Herschel will spend at least three years in orbit around the second Lagrange point of the Sun-Earth system known as L2.
Its mission is to study the formation of galaxies in the early Universe and their subsequent evolution, investigate the creation of stars and their interaction with the interstellar medium, observe the chemical composition of the atmospheres and surfaces of comets, planets and satellites, and xamine the molecular chemistry of the Universe.
ESA Herschel 1 »» ESA Herschel 2 »»
- James Webb Space Telescope. NASA is building the JWST, formerly known as the Next Generation Space Telescope (NGST), for launch in 2013.
Named for the space agency's second administrator, the Webb Space Telescope will be aboard a satellite in an orbit 940,000 miles out in space at the second Lagrange Point, or L2. There, the spacecraft will be balanced between the gravity of the Sun and the gravity of Earth, so a Sun shield on only one side of the satellite will be sufficient to protect the telescope from the light and heat of Sun and Earth.
JWST's instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range.
While the Webb may be seen as replacing the Hubble Space Telescope, it actually will observe a somewhat different region of the electromagnetic spectrum – from the far visible to the mid-infrared. The wavelength coverage differs from that of the Hubble, which sees a range from the ultraviolet to the near-infrared. The Webb will carry a near-infrared camera, a multi-object spectrometer, and a mid-infrared spectrometer camera.
JWST will have a large mirror, 6.5 meters (21.3 ft.) in diameter and a sunshield the size of a tennis court. Both the mirror and sunshade won't fit onto the rocket fully open, so both will fold up to be opened once JWST is in space.
JWST will find the first galaxies that formed in the early Universe, possibly connecting the Big Bang to our own Milky Way Galaxy. The telescope will peer through dusty clouds to see stars forming planetary systems, connecting the Milky Way to our own Solar System.
NASA JWST »» About James Webb »»
FUTURE HIGH-ENERGY ASTROPHYSICS OBSERVATORIES »»
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