After generations of astronomical observations, Puerto Rico's Arecibo Observatory has crashed.
The US National Science Foundation (NSF) said the 900-ton instrument base of the telescope dropped about 450ft (137m) down on a reflector dish.
It came only weeks after authorities revealed that the telescope would be demolished amid safety concerns following disruption to its support structure.
This radio telescope in Puerto Rico is one of the largest in the world.
For 57 years, it was a crucial research resource for radio astronomy. It was even made popular in the James Bond film GoldenEye and other Hollywood movies as the setting for a scene.
After the collapse, the NSF said there had been no reports of casualties.
What was going on with the telescope?
The NSF said the telescope collapsed on Tuesday, "resulting in damage to the dish and surrounding facilities" at around 06:55 am EST (11:55 am GMT).
The telescope consisted of a 1,000-ft large radio dish with a 450-ft above-hanging instrument base. Cables attached to three towers suspended the platform.
The NSF said an inquiry was underway into the platform's collapse.
"Initial findings indicate that the top section of all three of the... telescope's support towers broke off As the 900-ton instrument platform fell, the telescope's support cables also dropped," it said in a statement.
"Preliminary assessments indicate the observatory's learning centre sustained significant damage from falling cables," it said.
Since August, two cables have collapsed, destroying the structure and causing officials to shutter the observatory.
An analysis last month concluded that the telescope was at risk of disastrous failure and said that, without creating a potentially dangerous risk to construction employees, the massive structure could not be fixed.
As a senior science associate, Jonathan Friedman, who worked at and now lives near the observatory for 26 years, told the Associated Press news agency about the moment the telescope collapsed on Tuesday.
"It sounded like a rumble. I knew exactly what it was," he said. "I was screaming. Personally, I was out of control... I don't have words to express it. It's a very deep, terrible feeling."
NSF expressed its grief over the situation. The agency said it is looking for ways to assist the scientific community and maintain its strong relationship with the Puerto Ricans.
"Top priorities are maintaining safety at the site, conducting a complete damage assessment as quickly as possible, and taking action to contain and mitigate any environmental damage caused by the structure or its materials.
"While the telescope was a key part of the facility, the observatory has other scientific and educational infrastructure that NSF will work with stakeholders to bring back online," the agency said.
What is the telescope's history?
In the early 1960s, the telescope was designed to research the ionosphere, the ionized outer portion of the Earth's atmosphere. But it was soon used as an all-purpose radio observatory.
On the broader discipline, radio astronomy is a science that observes events in the Cosmos by observing radio frequencies. Various astronomical phenomena exhibit radiation at radio wavelengths, such as pulsars - magnetized, spinning stars.
The observatory presented the first solid evidence for a type of object known as a neutron star. It was also used to describe the first example of a binary pulsar that won its discoverers the Nobel Prize in Physics (two magnetised neutron stars orbiting around a similar mass centre).
The first definitive observation of exoplanets, celestial bodies circling other stars, was supported by the telescope in 1992.
It has also been used to respond to messages in the universe from intelligent life elsewhere and to detect asteroids near Earth.
The main dish has served as a location in films over the years, including GoldenEye, the first appearance of Pierce Brosnan as James Bond in 1995, and the 1997 science fiction thriller Touch, starring Jodie Foster and Matthew McConaughey.
The telescope is so loved that there was also a Change.org petition to save the observatory after announcing the dismantling. There were over 35,000 signatures on it.
After the officials announced their dismantling plans for the telescope, NASA released a statement.
The space agency said the Arecibo facility and its STEM education and other assets would continue while the 305m radio telescope is being decommissioned.
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