The drive to map the sky is as old as civilization itself. The Great Pyramids in Egypt point straight at specific stars. The ancient stone configuration Stonehenge in Britain is arranged to track the progress of the sun toward its northernmost point in the sky. The first astronomical observatories date back as early as the third century in the Middle East; at that time, astronomy was mixed up with astrology, and sky-watchers used cosmic measurements to predict the future. Since Islamic law forbids such superstition, many of the earliest astronomers were executed for heresy.
But during the Renaissance period in Europe, astronomy's ties to astrology were broken and it became a real science. In the late 16th century, Hans Lippershey, an eyeglass-maker in Holland, applied for the first telescope patent, claiming invention of a device that made distant objects on Earth appear closer. Soon after, Galileo Galilei in Italy turned his own telescope to the sky for the first time and saw incredible sights, like craters on the moon and four bodies orbiting Jupiter. His discoveries tended to fly in the face of religious dogma, though, and he had to retract much of what he said. Still, the telescope went on to completely change our understanding of the world beyond our planet.
What Galileo viewed through his "far looker" was a blurry mess compared to what we can see today. Not long after Galileo saw the moon up close, inventors like Johannes Kepler, Isaac Newton and N. Cassegrain made a succession of major innovations in telescope design. Since then, developments in our understanding of astrophysics, along with technological advancements in optics, engineering and rocket science have led to amazingly clear, distant views of our galaxy and far, far beyond. Current telescopes can even see matter disappear into a black hole.
And the telescope race is just heating up.
In this article, we'll look at 10 of the most amazing telescopes of our time, including several that are still on the drawing board and promise to reveal images of the Big Bang itself. Many of these new telescopes are funded partially by private donors. We'll begin with some of the greatest ground-based telescope systems in use today. Because they have to be able to see through the Earth's atmosphere, these telescopes are truly massive.
Technically speaking, the South African Large Telescope, or SALT, is the biggest telescope in the Southern Hemisphere. But when it comes to telescopes, how big is "big?"
10. Southern African Large Telescope
In an optical telescope, performance depends primarily on two characteristics: the ability to collect light bouncing off objects and the ability to focus that light to produce a clear image of those objects. The ability to collect light is directly related to aperture size, or the area available to capture light. In the huge telescopes of modern astronomy, one or more mirrors serve to collect light. The size of the mirror is the single most important determinant in how far a telescope can see, since the farther away an object is, the fainter the light bouncing off it.
It's mirror size that makes the Southern African Large Telescope (SALT), located just outside Sutherland, South Africa, stand out among the most amazing telescopes in the world. With an 11.1-meter (36.6-ft) aperture, SALT can see distant galaxies and quasars that are one billion times fainter than what can be seen with the human eye [source: GTC]. No one can manufacture a single mirror of that size, which is about the height of a three-story building, so SALT uses a collection of hexagonal mirrors pieced together into one perfectly smooth mirror. A single imperfection would distort the image it captures.
If we could see a candle flame on the moon with the naked eye, we'd have the optical acuity of SALT. However, while SALT comes in first with its 11-meter aperture, part of the telescope design blocks the edges of the mirror. Its actual aperture is more like 9.2 meters (30.18 ft) [source: GTC]. The Keck telescope system in Hawaii has a larger actual aperture, which makes it the second largest telescope system in the world.
9. Keck Observatory
At an altitude of 14,000 ft (4,267.2 meters), at the top of Hawaii's Mauna Kea peak, two massive telescopes scan the universe for answers to some big questions -- how old is the universe, and how quickly is it expanding? Each 300-ton, 8-story tall telescope has an actual aperture of 10 meters (33 ft) and can collect both visible and infrared light.
The massive mirrors that collect and focus light are, like SALT's mirror, an array of smaller mirrors arranged on a perfectly formed curve. The telescopes have inner cooling systems to protect against the flexing that can come with heat exposure. But one of the greatest parts of the system is a tiny mirror that's actually supposed to flex. Even on Mauna Kea, Keck has to deal with the distortion caused by Earth's gaseous atmosphere, which is the greatest enemy to ground-based telescopes. A 6-inch (15-cm) mirror in each telescope deforms its shape 670 times per second to make up for the effects of Earth's atmosphere on incoming light [source: SALT].
The result is a pair of telescopes that can see the past. Keck can pick up light that has been traveling for billions of years. By the time this faint light hits Keck's mirrors, the event that caused it is long gone. Keck is helping astronomers determine the age of the universe and its expansion rate as well as allowing them to watch the birth of stars in other galaxies.
If Keck can see back in time, imagine what the biggest telescope in the world, the Great Canary Telescope, can pick up with its chart-topping aperture.
8. Great Canary Telescope
The Great Canary Telescope (GCT), situated on a mountain on La Palma in the Great Canary Islands, cost $180 million to build. It claims the title of the biggest telescope in the world, with a light-collecting area 10.4 meters (34.3 ft) across.
The telescope gathers both visible and infrared light with a mirror made up of 36 smaller mirrors. The entire 10.4-meter aperture is used at all times, making it one of the greatest cosmic observers in the world. Like Keck, the GCT uses adaptive optics to correct for the distortion caused when light passes through Earth's atmosphere. In the Great Canary device, there are several deforming mirrors, and each changes shape more than one thousand times per second [source: GTC].
With its optical systems, the Great Canary Telescope can capture distant galaxies, black holes, and planets that orbit other stars besides the sun. It can capture light so old that it shows the birth of galaxies in the earliest days of the universe.
As large as a single telescope's aperture can get, none can compare to the power of several massive telescopes working together. While the light-collecting ability of one 8.2-meter (26.9-ft) telescope might fall short of the incredible Great Canary, the capacity of several of those telescopes working in tandem leaves the GTC in the dust. That's where the Very Large Telescope comes in.
7. Very Large Telescope
Imagine a car on the moon with its headlights on. If you could look up at the moon and see each of the headlights as a distinct point of light, you'd have the observational power of the Very Large Telescope (VLT).
The VLT is actually an array of telescopes. In an array, several telescopes work together as a single unit, effectively creating one massive device. Radio telescopes -- which pick up radio waves instead of light waves -- are often used in arrays, like the Very Large Array in New Mexico, which was featured in the movie "Contact," and the Very Large Baseline Array, which stretches across the United States, from Puerto Rico to Hawaii.
The VLT is an array of optical telescopes. It consists of four 8.2-meter (26.9-ft) telescopes, each of which is a large telescope in its own right. One of those telescopes, which can operate individually, too, can pick up light 4 billion times fainter than what we can see with our eyes -- that's four times fainter than what SALT can see. There are also four smaller telescopes that act as backups to boost the system.
The VLT can join up to three of the huge telescopes into a single unit, using underground mirrors to combine light from the individual telescopes into a unified beam. The result is a telescope system that can see objects at 25 times the resolution of each telescope on its own. The ultimate goal is to be able to join together all four large telescopes into an array with the light-collecting power of a single 50-meter (165-ft) telescope.
Another take on the array approach is the type of bimirror system used in the Large Binocular Telescope, possibly the most powerful telescope in the world.
6. Large Binocular Telescope
A massive, two-part telescope called the Large Binocular Telescope (LBT) has already achieved first light -- the first image collected by a new telescope -- on a mountain in Arizona. The binocular system uses two mirrors, each one with an aperture of 8.4 meters (27.56 ft). Unlike the duo or trio of 8.2-meter (26.9-ft) mirrors at work in the Very Large Telescope, LBT has both mirrors mounted on the same telescope. It's not an array -- it's a single, massive unit with two huge, light-collecting mirrors. The system collects as much light as a telescope with a single 11.8-meter (38.8-ft) aperture [source: Popular Mechanics].
While it's already operational, LBT is still getting up to speed. Billed by many as the most powerful telescope in the world because of its effective aperture, the system uses an innovative honeycomb structure for its huge mirrors instead of a solid surface [source: Popular Mechanics]. The mirrors have a smooth front and an open honeycomb matrix in back, making them much lighter than other mirrors and less prone to gravitational distortion.
When it's fully operational (projected by 2010) astronomers expect LBT to see planets circling stars well outside our own galaxy with 10 times the resolution of Hubble Space Telescope, aiding in the discovery of planets. They also believe it will capture the first clear images of the types of space dust and gas pockets that can develop into new galaxies.
All of the superlative ground-based telescopes have high-tech adaptive optics systems to correct for the effect of Earth's atmosphere. There is really only one way to improve such systems: avoid the atmosphere entirely. Space-based telescopes are a prime example of combining technologies to achieve amazing results.
Take Hubble, for instance...
5. Hubble Space Telescope
French inventor N. Cassegrain might be stunned to know his 1672 reflecting-telescope design, which was criticized by Newton at the time, is orbiting Earth in a satellite telescope called Hubble [source: Cartage].
No matter how big ground-based telescopes get, they will always face the issue of distortion caused by Earth's atmosphere. A smaller telescope deposited in space, beyond Earth's atmosphere, can avoid the issue entirely. The Hubble Space Telescope combines astronomy with rocket science and operates in Earth's orbit.
With an aperture of 2.4 meters (94.5 inches), Hubble is much smaller than state-of-the-art ground telescopes, but its resolution is comparable or better, since the light it collects has travelled only through the relative vacuum of space [source: Hubblesite.org]. Hubble captures faint light coming in from billions of light years from Earth, which means it can see events that occurred billions of years ago. Hubble helped scientists confirm that dark matter exists and narrow down the age of the universe to 13 or 14 billion years [source: Hubblesite.org].
Hubble captures incredible images of the universe, but it's not the best space telescope out there. The Chandra X-ray Observatory tops Hubble in revealing the hidden world.
4. Chandra X-ray Observatory
X-ray telescopes rely on higher-energy phenomena than light telescopes. Chandra records images of the universe by analyzing energy fluctuations on the level of X-rays, using a barrel-shaped series of mirrors that make up a total aperture of 2.7 meters (9 ft) [source: Harvard]. Because the images are based on much higher-frequency waves of energy, they're clearer than Hubble's, and Chandra is a more sensitive instrument -- 25 times more sensitive than any other X-ray telescope [source: Harvard]. It also orbits Earth 200 times farther out than Hubble, so it's able to see deeper into space, peering out about 10 billion light years from Earth.
Chandra X-ray observatory has recorded crystal clear images of supernova remnants, quasars, exploding stars, black holes, nebulae and dark matter, among other phenomena. Scientists believe that Chandra will make startling contributions to our understanding of the origins of life.
Chandra is certainly not the last word in space telescopes. The Next Generation Space Telescope is already in development. It will orbit the sun, not the Earth, and it could be launched by 2013 [source: FirstScience]. And like the space telescopes, ground-based devices are looking at a next generation, too.
The current state-of-the-art instruments are in the 8-to-10-meter (26.25-to-32.81-ft) aperture class. The next wave of telescopes will squash that. The race is on to build the biggest telescope ever, and the final three telescopes on our list are top contenders.
3. Giant Magellan Telescope
Much like the Large Binocular Telescope, the Giant Magellan Telescopes uses several mirrors in the same device. But instead of two 8.4-meter (27.56-ft) mirrors, Magellan has seven.
It's a $500 million project funded by several universities in the United States and Australia, along with two U.S. research institutes. Its seven mirrors, arranged with six segments surrounding a single central mirror, combine to create a telescope with an approximate 24-meter (80-foot) primary mirror. Based in Las Campanas, Chile, the telescope has an adaptive optics system that can cancel out atmospheric distortion to the point of producing images with 10 times Hubble's resolution [source: Wired]. Projected for completion by 2016, astronomers expect Magellan to contribute to our understanding of the origins of life (one of the main themes in modern astronomy) by picking up light that began its journey billions of years ago.
While a 24-meter (78.74-ft) aperture dwarfs the current largest Great Canary Telescope, the next telescope on the list takes it up another notch. And it has the price tag to prove it.
2. Thirty Meter Telescope
The name says it all. The Thirty Meter Telescope's massive primary mirror has 492 segments, all perfectly aligned to form a 30-meter (98-foot) light-collecting surface. Each segment will be continuously computer-adjusted to maintain the correct alignment to prevent any image distortion. Its adaptive optics correct not only for atmospheric distortion but also for ground winds that can alter observational accuracy.
The telescope will cost about $780 million and is funded in part by Intel co-founder Gordon Moore [source: RedOrbit]. It's expected to have 12 times the resolution of Hubble Space Telescope. With a $200 million Moore Foundation grant, the Thirty Meter Telescope is the closest of the next-generation devices to full funding. The telescope could be under construction as early as 2009 and ready for first light by 2016.
The Thirty Meter Telescope will be eight times more powerful than any current ground-based system [source: Discovery News]. But of the three next-generation ground-based telescopes on the list, none is as ambitious as our final entry. Europe is aiming to create a telescope that wipes out the competition.
1. European Extremely Large Telescope
At a cost of $1.17 billion, the European Extremely Large Telescope (ELT) is aiming high. The Chile-based project, funded by a consortium of European Union countries, is building a telescope with a 42-meter (138-ft) mirror. The original design called for a 100-meter (330-ft) mirror but was downsized for practical reasons.
Still, 42 meters is nothing to sneeze at. This new class of telescope -- the 30-to-50-meter class -- is only possible because engineers have come up with new ways to build mirrors. The number of segments they can piece together into a perfect surface has grown from the dozens to the hundreds, meaning the possibilities of what these new telescopes can see is nearly endless.
As for the ELT, astronomers are predicting the discovery of new planets and entire planetary systems, as well as revealing the events that gave birth to the universe. As early as 2018, the 21-story-tall telescope should add dramatically to our knowledge across the field of astrophysics, providing insight into dark matter and dark energy, the space-time continuum and the inner workings of super-massive black holes.
With both private and public sources pumping hundreds of millions of dollars into telescopes, our ability to see into the farthest corners of the universe -- and into the farthest corners of time -- appears to be limited only by how quickly we can build bigger instruments. No one knows just what we'll see when the next-generation ground- and space-based telescopes start delivering their images.
For more information on telescopes, including upcoming projects and details on how these and other telescopes work, look at the links on the next page.
Lots More Information
- Milky Way Pictures
- Black Hole Pictures
- Spaced Out: Hole in the Universe Quiz
- Mars Pictures
- Physical Cosmology Puzzles
More Great Links
- First Science.com: The Great Telescope Race - August 10, 2004
- Popular Mechanics.com: The World's Most Powerful Telescope - May 2006
- redOrbit: New Technologies Fuel Powerful Telescope Race - April 24, 2008
- The Chandra Mission. Harvard-Smithsonian Center for Astrophysics. http://chandra.harvard.edu/about/axaf_mission.html
- E-ELT. ESO.org. http://www.eso.org/public/astronomy/projects/e-elt.html
- Giant Magellan Telescope: Technical Overview. GMTO.org http://www.gmto.org/tech_overview
- The Great Telescope Race. First Science.com. August 10, 2004. http://www.firstscience.com/home/articles/technology/the-great-telescope-race_1522.html
- History of Telescope. Cartage.org. http://www.cartage.org.lb/en/themes/sciences/Astronomy/Equipementdevices/Telescope/Historyoftelescope/mainpage.htm
- How Hubble Space Telescope Works. HowStuffWorks.com. http://www.howstuffworks.com/hubble.htm
- New Technologies Fuel Powerful Telescope Race. redOrbit. April 24, 2008. http://www.redorbit.com/news/space/1356023/new_technologies_fuel_powerful_telescope_race/index.html?source=r_space
- An Overview of the Very Large Array (VLA). National Radio Astronomy Observatory. http://www.vla.nrao.edu/genpub/overview/
- Paranal Observatory. ESO.org. http://www.eso.org/public/astronomy/teles-instr/paranal.html
- The Race to Build the Biggest, Baddest Telescope Continues. WiredScience. April 21, 2008. http://blog.wired.com/wiredscience/2008/04/the-race-to-bui.html
- Southern African Large Telescope http://www.salt.ac.za/
- What is the GTC? Gran Telescopio CANARIAS. http://www.gtc.iac.es/en/pages/gtc/gtc.php
- W.M. Keck Observatory. https://www.keckobservatory.org/about.php
- The World's Biggest Telescope. Popular Science.com. December 2007. http://www.popsci.com/military-aviation-space/article/2007-12/worlds-biggest-telescope
- World's Biggest Telescope in the Works. Discovery.com. Dec. 20, 2007. /news/2007/12/20/gift-telescope.html
- World's largest optical telescope to see first light. New Scientist.com. July 13, 2007. http://space.newscientist.com/article/dn12266-worlds-largest-optical-telescope-to-see-first-light.html
- The World's Most Powerful Telescope. Popular Mechanics.com. May 2006. http://www.popularmechanics.com/science/air_space/2703416.html