Giant telescope's own powerful radiation may have contributed to collapse

Powerful electromagnetic radiation from an enormous radio telescope in Puerto Rico may have fast-tracked structural damage that led to the instrument's collapse in 2020, a new report says. 

For over a half-century, the Arecibo Observatory's 1,000-foot-wide telescope, a giant bowl nestled in a lush valley, was the leading radio transmitter on Earth. The facility advanced astronomy through the study of stars, exoplanets, and asteroids, as well as searched for signals from potential alien civilizations in space. The telescope even had its proverbial 15 minutes of fame with cameos in the sci-fi film Contact, starring Jodie Foster, and the James Bond blockbuster, GoldenEye. 

On Dec. 1, 2020, a 900-ton platform and four-story dome of secondary reflectors hanging over the receiver fell more than 400 feet and crashed into the main dish. No people were hurt in the incident, but the U.S. National Science Foundation, which owned the telescope, decided not to rebuild the observatory, dashing the hopes of astronomers around the globe who relied on it for their research. 

Previous investigations into the disaster attributed the structural failure to slow "zinc creep," the tendency for zinc to deform over time under tension. Sockets filled with zinc anchored a set of cables holding the main platform over the reflector dish. Gradually, the zinc lost its grip and allowed several of the supporting wires to slip out. 

But the Arecibo Observatory collapse was unlike anything that had ever happened before. It is believed to be the first documented case of a long-term zinc failure, and the zinc deformed at a load less than half the sockets' normal strength. 

"The baffling question was, 'Why was there excessive zinc creep at such loading?' Such a failure had never been reported previously in over a century of widespread zinc spelter socket successful use," Roger L. McCarthy, chair of the National Academies of Sciences, Engineering, and Medicine committee assigned to study the causes of the telescope's collapse, said in the incident report.

SEE ALSO: Webb telescope finds hot young star Vega is actually quite lonely An aerial view shows the damage to the Arecibo telescope after a cataclysmic collapse on Dec. 1, 2020. Credit: Ricardo Arduengo / AFP / Getty Images

The National Academies' recently released 98-page reportlargely agrees with previous forensic analyses on the sequence of events that led to the collapse, including a study performed by NASAin 2021. 

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But the new report criticizes other investigations for not including several previously observed failure patterns at the site leading up to the event and for not providing explanations for them. The committee asserts there were warning signs that structural engineers didn't heed. 

McCarthy, founder and owner of McCarthy Engineering, labeled the accident "one of the most publicized and baffling failures of the modern era."

The damage, according to the committee, began with Hurricane Maria, more than three years before the collapse. Following the 2017 storm, inspectors saw "large and progressive" cable pull-outs. Those discoveries should have prompted immediate repairs, the committee said, but the inspectors hadn't accounted for how fast that damage would progress. 

" ... One of the most publicized and baffling failures of the modern era."

In August 2020, about four months before the collapse, an auxiliary cable snapped, causing a 100-foot gash on the dish and damaging the suspended platform. The problems only snowballed, with a main cable breaking that November. Just 12 days before the whole telescope fell apart, the National Science Foundation announced it would be closing the facility, due to its dangerous state of disrepair. 

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Originally, the telescope was built in the 1960s through the Defense Department to help develop anti-ballistic missile defenses. Later, a pair of scientists won a Nobel Prizein physics in 1993 for using the telescope to observe a new type of pulsar, a fast-spinning dead star core left over after a supernova. The discovery has provided a new "space laboratory" for studying gravitation. 

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Despite its perilous location in the Caribbean, the telescope had survived many hurricanes without issue over its 57 years of operation.

The committee thinks electromagnetic waves from the Arecibo telescope itself could have sped up the zinc deformity. Electroplasticity is a phenomenon that can occur when an electric current passes through a material, causing it to become more flexible and lose its original shape. 

In a 1989 archival photo, a technician checks cables suspending a platform over the Arecibo telescope about 450 feet in the air. Credit: Roger Ressmeyer / Corbis / VCG via Getty Images

The group of subject-matter experts has recommended that the foundation give the remaining sockets and cables from the site to the research community for studies into this hypothesis to capture hard evidence. 

"Unfortunately, there was not enough data available to prove our explanation," McCarthy said in a statement. "It is simply the most plausible hypothesis based on the data we do have."

It's too late to help Arecibo. Instead of rebuilding the observatory, the foundation is funding a new science, technology, engineering, and math education centerat the site. But understanding what happened could prevent similar damage to other facilities in the future.