The dish of Arecibo Observatory’s radio telescope lies heavily damaged following the collapse of the instrument platform on Dec. 1, 2020.
Credit: © estadespr, Shutterstock

The year 2020 claimed yet another victim, with the destruction of one of the most impressive telescopes ever built—the radio telescope at Arecibo Observatory. Already damaged beyond repair, the remaining cables that held the telescope’s instrument platform snapped on December 1, sending the platform crashing through the dish below. It was a spectacular and disappointing end to a telescope that has done so much to further our understanding of the universe.

The radio telescope was the primary instrument at the observatory, located in Puerto Rico, 50 miles (80 kilometers) west of San Juan. A radio telescope collects and measures radio waves given off by objects in space. At 1,000 feet (305 meters) in diameter, the Arecibo radio telescope was the world’s most powerful when it opened in 1963. It remained the largest dish (bowl-shaped reflector) in the world until 2016, when the dish of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) was completed in Guizhou Province, China.

The Arecibo dish was built into a natural basin-shaped valley. The dish focused radio waves onto receivers mounted on the large instrument platform suspended above. The waves came from such distant objects as pulsars (rapidly spinning stars whose waves arrive on Earth as regular pulses). Arecibo astronomers discovered the first binary pulsar (a pulsar in orbit around a companion star) in 1974. In the early 1990′s, astronomers at the observatory discovered planets beyond the solar system and ice at the poles of Mercury. Until the middle of 2020, astronomers were using the radio telescope for a variety of astronomical observations, including monitoring and assessing the threat level of near-Earth asteroids.

The Arecibo Observatory radio telescope as it appeared before its collapse in 2020. The instrument platform (top center) crashed through the dish on December 1.
Credit: © Than Tibbetts, Shutterstock

The impressive appearance of the massive dish surrounded by the lush, forested hills of Puerto Rico’s interior seemed particularly to capture the public imagination. The radio telescope appeared in the sci-fi motion picture Contact (1997) and the James Bond film GoldenEye (1995), for example.

The final collapse of the telescope began in August 2020, when an auxiliary cable that held the instrument platform broke. The falling cable tore several large gashes in the dish. In November, before engineers had a chance to repair the dish or replace the cable, a main support cable broke. The United States National Science Foundation (NSF) quickly determined that the telescope could no longer be saved without putting lives at risk. The NSF was considering plans to decommission the telescope—taking it permanently out of service—when the collapse occurred.

The future of the Arecibo Observatory appears doubtful. The U.S. Congress could direct funds to replace the telescope, but it may be more likely that the facility will be closed permanently.

In 1975, scientists engaged in the search for extraterrestrial intelligence used the dish from the Arecibo telescope to beam a powerful signal into space. This signal was designed by astronomer Frank Drake with the help of famous science popularizer Carl Sagan to give any intelligent being who discovers it information about Earth and humans. Encoded within the message was an image of the dish itself. Although it is unlikely that any alien civilizations will receive the message, it serves a lasting monument to the telescope’s legacy.

July 20, 2016

On Saturday, July 16, a South African meerkat made international news, but it wasn’t one of the cute and cuddly critters of TV’s “Meerkat Manor.” This meerkat—or, rather, MeerKAT—is a radio telescope complex under construction near Carnarvon, South Africa, south of where the TV series studied actual meerkats in the Kalahari Desert. On Saturday, images from the first 16 MeerKAT reflectors (dish antennas)—in operation for only a few hours and looking at only a tiny corner of the universe—revealed black holes some 200 million light-years away and hundreds of previously unknown galaxies. A radio telescope consists of a radio receiver with an antenna fixed on a wide bowl-shaped reflector that records radio waves coming from stars and other objects in outer space. A radio receiver amplifies the signals and sends them to a computer. The computer then analyzes the radio spectrum of the wave source to produce an image.

A MeerKAT dish antenna scans the night sky above the dry Karoo region of South Africa.
Credit: © SKA South Africa

The KAT in MeerKAT stands for Karoo Array Telescope, which refers to the complex’s location in South Africa’s remote Karoo semidesert region. MeerKAT, which will have 64 reflectors when completed late next year, is the first phase of Square Kilometer Array (SKA) South Africa that will eventually have 250 antennas. SKA South Africa will then pair with a SKA complex of 256 antennas being built in Western Australia. Together, they will explore and measure the universe at different radio frequencies. If the first few hours of the first 16 SKA reflectors are any indication—which glimpsed less than 1/100^th of 1 percent of the celestial sphere—imagine what 64, then 250, then 506 antennas mapping huge areas of the sky might find!

This portion of MeerKAT’s first radio image shows more than 200 astronomical radio sources (white dots). Previous mapping of this area showed just five sources, marked here by the violet circles.
Credit: © SKA South Africa

But wait, there’s more! This is only SKA Phase 1. SKA Phase 2—scheduled to be operating by the mid-2020’s—will eventually include thousands of radio telescope antennas throughout Africa and Australia. The SKA project will no doubt enhance our understanding of the universe and may possibly even change it. It will also test our current understanding of physics and expand our technological grasp. SKA has a number of key objectives, such as investigating the origins and structure of the universe and studying gravitational waves and astrobiological (the search for and study of life in the universe) possibilities. But the project’s statement purpose, “Exploration of the Unknown,” reflects the expectation that SKA will discover things we cannot yet conceive.

January 25, 2013

In a bold venture, a group of scientists is taking steps to make the first-ever image of an invisible black hole, one of the most mysterious objects in the universe. Their target is the black hole at the center of our own galaxy, the Milky Way. (Each of the billions of galaxies in the universe is thought to harbor a massive black hole at its center.) The group, led by Sheperd Doeleman of the Massachusetts Institute of Technology, plans to utiltize as many as 50 radio telescopes to do the job. The scientists will essentially turn the network of telescopes into one giant telescope the size of the Earth itself. They are calling this network the Event Horizon Telescope. Radio telescopes have been chosen for the job because, unlike other types of telescopes, they can “see through” the cloud of dust and gas that surrounds a black hole. The data from the telescopes will be fed into a computer, which will be used to create the image.

Black holes are regions of space whose gravitational force is so strong that nothing can escape from them–not even light. They are believed to be the remains of stars that died in massive explosions called supernovae. The black area around a black hole is known as the event horizon. Astronomers use the radius of the event horizon to specify the size of a black hole. No one has yet discovered a black hole for certain. The fundamental descriptions of black holes are based on equations in the theory of general relativity developed by the German-born American physicist Albert Einstein. The theory was published in 1916.

A supermassive black hole sucks in a swirling disk of matter, shooting out beams of particles in this artist’s conception. A black hole is a region of space whose gravitational force is so strong that nothing—not even light—can escape from it. A supermassive black hole has a mass from millions to billions of times that of the sun. (NASA)

Scientists have never before imaged a black hole directly. The visual evidence for these objects comes from the behavior of other objects around them. The scientists hope to image the black hole to answer basic questions about them. For example, Einstein predicted that the event horizon is a perfect circle. If the black hole was slightly flattened or distorted from a perfect sphere in some way, Einstein’s theory would need to be revised or discarded. The measurements will be taken over several years using telescopes from around the world.

Additional World Book artices:

• Gravitational wave
• A Cosmic Assignment (a special report)
• The Search for Gravity Waves (a special report)
• Telescopes: 400 Years of Stargazing (a special report)
• The Universe on the Grand Scale (a special report)

Feb. 24, 2012

Russian scientists are beginning to examine the first images made by their country’s new RadioAstron space telescope, now the largest space telescope in Earth orbit. Launched with little fanfare in July 2011, the radio telescope has a collecting dish 33 feet (10 meters) wide. By comparison, the collecting mirror aboard the Hubble Space Telescope is 8 feet (2.4 meters) wide. The RadioAstron space telescope is funded and run by Russia’s Astro Space Center in Moscow and is part of an international network of ground-based radio telescopes spread around the world. The new space telescope will help astronomers view such objects as supermassive black holes in the center of distant galaxies, cosmic rays, dark matter, neutron stars, and new planetary systems. The telescope began science operations in December 2011.

Radio telescopes collect and measure faint radio waves given off by objects in space. Instead of the mirrors and lenses used in optical telescopes, radio telescopes use a large dish that looks much like a satellite dish. Numerous radio telescopes can be linked together, a technique called interferometry. With this technique, scientists can create a telescope equal to the distance between the telescopes. For example, a network of telescopes spread around Earth would have the power of one telescope with a dish the diameter of Earth, about 8,000 miles (12,800 kilometers) wide. The RadioAstron space telescope travels in a highly elliptical (oval) orbit around Earth. This orbit takes the satellite as far away as 240,000 miles (390,000 kilometers). At that distance, the linked telescopes have the power of one dish 240,000 miles wide–about the distance from Earth to the moon.

An astronomer studies an image produced by the Expanded Very Large Array of radio telescopes at Socorro, New Mexico. The colors in the "painting" represent different amounts of radio energy sent out by objects in the sky. National Radio Astronomy Observatory

 

Additional World Book articles:

• Astronomy
• Green Bank Telescope
• National Radio Astronomy Observatory
• Telescopes: 400 Years of Stargazing (A Special Report)