59 Fun Facts About Telescopes

From which language do the roots of the word 'telescope' come, meaning 'far' and 'to look'?

Greek. Tele means 'far' and skopos 'watcher'; the name is said to have been coined in 1611 at Rome's Lincean Academy, for an instrument its new member Galileo was showing.

Galileo's telescope revealed four moons circling which planet in January 1610?

Jupiter. Galileo first took the points of light beside it for fixed stars, then saw that they had moved by the next night and concluded they were circling the planet.

Edwin Hubble showed in the 1920s that other galaxies exist after spotting a pulsing star in which one?

The Andromeda Galaxy. On photographs from the 100-inch telescope, Hubble found a star whose steady pulsing gave away its distance, far too great for it to lie inside the Milky Way.

Which Middelburg spectacle-maker filed the earliest known telescope patent application in 1608?

Hans Lippershey. He never got his patent, yet the States General paid him handsomely to make several versions of the instrument built for both eyes.

The twin Keck telescopes stand near the summit of which Hawaiian volcano?

Mauna Kea. Each 10-metre mirror is made of 36 hexagonal segments, which computers nudge back into line twice a second as the telescope turns.

Galileo, then a professor at nearby Padua, presented his telescope to which city's senate in 1609 and had his salary doubled?

Venice. He had first heard of the spyglass there earlier that year and, by his own account, worked out how to build one on the night he got home.

Galileo's lens design, a convex objective with a concave eyepiece, is still used today in which viewing device?

Opera glasses. The pairing gives an upright image in a short tube, handy in a theatre, but its narrow field of view led astronomers to drop it for a design that shows the sky upside down.

Which astronomer described in 1611 a telescope with a convex objective and a convex eyepiece?

Johannes Kepler. He only described the design on paper, and it caught on some twenty years later, after the Jesuit Christoph Scheiner built such telescopes and found the view far wider.

Christiaan Huygens discovered which moon in 1655 with a telescope he built himself?

Titan. Huygens called it simply 'Luna Saturni', Saturn's moon, and the European probe that parachuted to its surface in 2005 was named Huygens after him.

What were the very long tubeless refractors of the late 17th century, their lenses mounted on tall poles, called?

Aerial telescopes. Christiaan Huygens set the lens on a high mast and aimed it from the ground with a taut string, since very long focal lengths cut the colour fringes of simple lenses.

Who built the first practical reflecting telescope in 1668?

Isaac Newton. He was convinced that any lens must smear starlight into colours, so he cast and polished a small metal mirror himself and built a telescope only about six inches long.

What tin-copper alloy was standard for telescope mirrors into the 19th century?

Speculum metal. It tarnished so quickly that the big telescopes kept a second mirror on hand, to swap in while the first was away being repolished.

Europe's Very Large Telescope stands on a mountaintop in which desert?

The Atacama. The Chilean desert's high, dry air also drew ALMA, an array of 66 radio dishes on a plateau 5,000 metres above sea level.

In the Cassegrain reflector, published in 1672, light leaves the tube through what?

A central hole in the main mirror. A small convex mirror bounces the light back down through it, packing a long focal length into a short tube, and the layout came to dominate large telescopes.

Jocelyn Bell found which new kind of object in 1967 as a 'bit of scruff' on her radio telescope's charts?

Pulsars. The pulses came so regularly, every one and a third seconds, that the first one was nicknamed 'little green men'; the Nobel Prize that followed went to others, not to her.

What does an achromatic lens combine to bring red and blue light to the same focus?

Two kinds of glass. A convex lens of ordinary crown glass spreads the colours apart, and a concave lens of leaded 'flint' glass bends them back together.

In which 1997 film does an astronomer pick up an alien signal at New Mexico's Very Large Array?

Contact. The array's 27 working dishes are moved along railway tracks, so they can be spread along arms up to 21 km long to zoom in on fine detail or packed into a patch about a kilometre across.

Which planet was discovered in 1781 by a musician using a homemade telescope?

Uranus. William Herschel first reported it as a comet, and it took about two years for astronomers to agree he had found a new planet, the first ever discovered with a telescope.

What did William Herschel do in his giant reflectors so that no second mirror was needed?

Tilted the main mirror. Herschel stood in a cage at the mouth of the tube and looked down at the image directly, a real gain when metal mirrors wasted so much of the light.

Who built the 72-inch 'Leviathan of Parsonstown', the world's largest telescope for some seventy years from 1845?

Lord Rosse. Through it the Irish earl found that some 'nebulae' are spirals, long before anyone knew they were galaxies far beyond our own.

Which French physicist began coating glass telescope mirrors with silver in 1857, independently of a German rival?

Léon Foucault. The man behind the famous pendulum showed that a silver film on glass reflected far more light than a metal mirror and could simply be stripped off and renewed when it tarnished.

The University of Chicago built Yerkes Observatory, with its record 40-inch refracting telescope, in which neighbouring state?

Wisconsin. Astronomer George Ellery Hale talked Chicago streetcar tycoon Charles Yerkes into paying for the world's largest refractor, and its lens went to Williams Bay in 1897.

Why do telescope lenses top out near one metre?

They sag under their own weight. A lens can be gripped only around its rim, while a mirror can be supported across its whole back, which is why the giants of the past century are all reflectors.

The 100-inch Hooker telescope, the world's largest from 1917 to 1949, is on which California mountain?

Mount Wilson. Los Angeles merchant John D. Hooker put up the seed money for the mirror, and with the finished telescope Edwin Hubble found that the universe is expanding.

The 200-inch Hale Telescope at Palomar has a primary mirror made of which glass?

Pyrex. General Electric first tried and failed to make the disc from fused quartz, so the project turned to Corning's low-expansion glass, sold under a name better known from kitchenware.

Which country built the six-metre telescope that took the 'world's largest' title from California's Hale Telescope in the 1970s?

The Soviet Union. Its BTA, short for 'Big Telescope Alt-azimuth', stands in the Caucasus, and the computer-steered mount in its name became the standard for the giants that followed.

As William Herschel called down from his telescope, which relative sat at a window recording his observations?

His sister Caroline. When William pulled a string she opened the window and wrote down what he shouted, did the calculations by day, and found several comets in sky sweeps of her own.

Which low-cost telescope design on a simple wooden mount is named after a San Francisco monk who built them from salvage?

The Dobsonian. John Dobson made big reflectors from ship portholes and cardboard tubes, lost his place in the monastery over the hobby, and spent decades showing the sky to passers-by.

Which Bell Labs engineer first detected radio waves from space in 1932?

Karl Jansky. Sent to hunt the static that spoiled radio telephone calls, he found a faint hiss that returned four minutes earlier each day, keeping time with the stars and not the Sun.

Where did engineer Grote Reber build the first dish radio telescope, at his own expense, in 1937?

In his back yard. Reber, of Wheaton, Illinois, used the 31-foot dish to make the first survey of the radio sky, working at night because sparks from passing car engines drowned the signal by day.

What is combining signals from several dishes into a virtual high-resolution telescope called?

Aperture synthesis. Martin Ryle spread a few small dishes over several kilometres and let the Earth's own rotation sweep them round, mimicking one enormous telescope; it won him a share of the 1974 Nobel Prize.

The Arecibo radio telescope stood on which island until its 2020 collapse?

Puerto Rico. The 305-metre dish, the world's largest for over fifty years, lay in a natural sinkhole until December 2020, when the instrument platform hung above it broke loose and crashed into it.

The climactic fight of which James Bond film was staged at the Arecibo Telescope?

GoldenEye. The film passes the dish off as a villain's hidden antenna that rises from a drained lake in Cuba, and Bond's last fight plays out on the platform slung high above it.

Which country took the 'largest single-dish telescope' record from Arecibo in 2016 with its 500-metre FAST?

China. FAST's dish fills a natural hollow in the hills of Guizhou province, and its surface of nearly 4,500 panels flexes in real time to stay focused on a target.

The Event Horizon Telescope's first black hole image, in 2019, showed which galaxy's core, three years before the Milky Way's?

Messier 87. Eight radio observatories around the globe were linked into one Earth-sized telescope to see it: a glowing ring around a black hole 6.5 billion times the mass of the Sun.

Melipal, one of the Very Large Telescope's four units, takes its Mapuche name from which star pattern?

The Southern Cross. The other three units are named for the Sun, the Moon and the evening star, though ESO first announced that last name, Yepun, as Sirius.

The 10.4-metre Gran Telescopio Canarias, as of 2025 the largest single-aperture optical telescope, is on which island?

La Palma. It stands on the rim of the Caldera de Taburiente, more than 2,000 metres up, under skies so good for astronomy that the site hosts one of the Northern Hemisphere's largest gatherings of telescopes.

About how wide is the main mirror designed for ESO's Extremely Large Telescope?

About 39 metres. No single piece of glass could span that, so the mirror is a mosaic of 798 hexagonal segments, each roughly a metre and a half across.

Why must X-ray and gamma-ray telescopes be placed on satellites or high-altitude balloons?

The atmosphere blocks those rays. The air that shields life on the ground kept X-ray astronomy waiting for rockets, and a 1962 flight caught the first X-rays from beyond the Solar System.

Which physicist bet that Cygnus X-1, an X-ray source found by a 1964 rocket flight, held no black hole?

Stephen Hawking. He made the wager with fellow physicist Kip Thorne and lost it, as years of observations showed that Cygnus X-1 does hold a black hole.

NASA's Chandra X-ray Observatory, launched in 1999, is named after which Nobel-winning astrophysicist?

Subrahmanyan Chandrasekhar. The name was chosen in a public contest in 1998: he was known simply as Chandra, a word that also means 'moon' or 'luminous' in Sanskrit.

About how wide is the Hubble Space Telescope's main mirror?

2.4 metres. That is slightly smaller than the 100-inch mirror Edwin Hubble himself used in the 1920s, so the space telescope's edge comes from where it flies, not from its size.

What was wrong with Hubble's main mirror when it launched in 1990?

It was the wrong shape. A lens set 1.3 millimetres out of place in the test rig left the mirror's edge slightly too flat, blurring every image until astronauts fitted corrective optics in 1993.

Hubble's 1995 photograph 'Pillars of Creation' shows towering columns of gas and dust in which nebula?

The Eagle Nebula. The pillars are several light-years tall, and they are slowly being boiled away by the fierce ultraviolet light of the young, massive stars that formed beside them.

The James Webb Space Telescope observes mainly in which part of the spectrum?

Infrared. The light of the earliest galaxies has been stretched into those wavelengths on its way here, so Webb can study an era that visible-light telescopes cannot see.

What did NASA's Kepler space telescope monitor in order to find exoplanets?

The brightness of about 150,000 stars. A planet crossing in front of its star dims it by a tiny, regular amount, and from those repeating dips Kepler found thousands of planets.

The James Webb Space Telescope finally launched in 2021 on which holiday?

Christmas Day. Folded up to fit inside its rocket, the telescope spent the following weeks unfurling its sunshield and mirrors on the way to its station, which it reached in January 2022.

The Webb telescope's 6.5-metre primary mirror has 18 hexagonal segments of which metal?

Gold-plated beryllium. Beryllium is very strong for its weight and holds its shape in the deep cold of space, while the thin film of gold makes each segment a better reflector.

Roughly how far from Earth is the Sun–Earth L2 point where the James Webb Space Telescope operates?

About 1.5 million km. That is roughly four times as far away as the Moon, well beyond the reach of astronauts, so unlike Hubble the telescope can never be repaired by a visiting crew.

James Webb, after whom the space telescope is named, held what job from 1961 to 1968?

NASA administrator. Webb, a lawyer by training, ran the agency through the build-up to Apollo and insisted it balance crewed flights with science, which is why his name went on the telescope in 2002.

Clyde Tombaugh found which distant world in 1930 on photographs taken with a telescope at Arizona's Lowell Observatory?

Pluto. The name came from Venetia Burney, an 11-year-old girl in Oxford, who suggested the Roman god of the underworld to her grandfather when the news broke.

Britain's newly finished Lovell Telescope at Jodrell Bank won fame by tracking the rocket that launched which satellite?

Sputnik 1. Anyone with a household radio could hear the satellite's beeps, but the giant dish, still deep in money troubles, followed its carrier rocket by radar with meteor equipment rushed into place.

Which Space Shuttle carried the Hubble Space Telescope into orbit in April 1990?

Discovery. The telescope was ready by 1985, but the Challenger accident grounded the shuttle fleet, and the finished Hubble sat in a clean room for years waiting for its ride.

Whose 1946 paper on an 'extraterrestrial observatory' began the history of the Hubble telescope?

Lyman Spitzer. The Princeton astrophysicist made the idea the cause of his career, spending decades winning over sceptical astronomers before the telescope finally flew in 1990.

Which company polished the Hubble Space Telescope's main mirror?

Perkin-Elmer. NASA made it subcontract a backup mirror to Kodak in case its new polishing methods failed; the spare never flew and is now on display at the National Air and Space Museum.

What was the second shuttle on the pad for during Hubble's 2009 repair?

Crew rescue. NASA had cancelled the flight as too risky after the Columbia accident, and revived it only with Endeavour standing ready to fetch Atlantis's astronauts.

In which Maryland city is the Space Telescope Science Institute, which selects Hubble's targets?

Baltimore. Astronomers wanted an independent institute, not NASA itself, to decide what Hubble looks at, and in 1981 it was sited on the Johns Hopkins University campus.

Which rocket launched the James Webb Space Telescope from French Guiana?

Ariane 5. The launch was so precise that Webb needed less fuel to correct its course, leaving enough propellant to keep working well beyond its planned ten years.

The Webb telescope's sunshield is roughly the size of what?

Tennis court. Too wide for any rocket, the shield launched folded up and unfurled in space, where its five hair-thin layers keep the telescope about 300 °C colder than its sunlit side.