“A huge, already damaged Arecibo radio telescope in Puerto Rico has completely collapsed after its 900-ton receiver platform fell onto the reflector dish below.
The telescope has played a key role in astronomical discoveries for more than half a century and entered popular culture with appearances in Hollywood films like GoldenEye and Contact.
The US National Science Foundation (NSF) had earlier announced that the Arecibo Observatory would be closed.
An auxiliary cable snapped in August, causing a wide gash on the 305-metre-wide dish and damaging the receiver platform that hung above it.
Then a main cable broke in early November.
‘A huge loss’
The collapse stunned many scientists who had relied on what had been the largest radio telescope in the world.
“It sounded like a rumble. I knew exactly what it was,” said Jonathan Friedman, who worked for 26 years as a senior research associate at the observatory and still lives near it.
“I was screaming. Personally, I was out of control … I don’t have words to express it. It’s a very deep, terrible feeling.”
Dr Friedman ran up a small hill near his home and confirmed his suspicions: A cloud of dust hung in the air where the structure once stood, demolishing hopes held by some scientists that the telescope could somehow be repaired.
“It’s a huge loss,” said Carmen Pantoja, an astronomer and professor at the University of Puerto Rico who used the telescope for her doctorate.
“It was a chapter of my life.”
Scientists around the world had been petitioning US officials and others to reverse the NSF’s decision to close the observatory.
The NSF said at the time that it intended to eventually reopen the visitor centre and restore operations at the observatory’s remaining assets.
The telescope was built in the 1960s with money from the US Defense Department amid a push to develop anti-ballistic missile defences.
It had endured hurricanes, tropical humidity and a recent string of earthquakes in its 57 years of operation.
The telescope has been used to track asteroids on a path to Earth, conduct research that led to a Nobel Prize and determine if a planet is potentially habitable.
The telescope also served as a training ground for graduate students and drew about 90,000 visitors a year.
“I am one of those students who visited it when young and got inspired,” said Abel Méndez, a physics and astrobiology professor at the University of Puerto Rico at Arecibo who has used the telescope for research.
“The world without the observatory loses, but Puerto Rico loses even more.”
He last used the telescope on August 6, just days before a socket holding the auxiliary cable that snapped failed in what experts believe could be a manufacturing error.
The NSF, which owns the observatory, said crews who evaluated the structure after the first incident determined that the remaining cables could handle the additional weight.
But on November 6, another cable broke.
A spokesman for the observatory said there would be no immediate comment, and a spokeswoman for the University of Central Florida did not return requests for comment.
Scientists had used the telescope to study pulsars to detect gravitational waves as well as search for neutral hydrogen, which can reveal how certain cosmic structures are formed.
About 250 scientists worldwide had been using the observatory when it closed in August, including Mr Méndez, who was studying stars to detect habitable planets.
“I’m trying to recover,” he said.
“I am still very much affected.”“