What happened to the Arecibo Telescope? (Beginner)

I read a news article recently that the Arecibo telescope would be shutting down. What happened?

Arecibo was one of the biggest telescopes in existence, with a diameter of 1000 feet! It was built in the 1960s in a sinkhole in Puerto Rico to study the ionosphere (one of the upper layers of Earth's atmosphere), but since then it has also served as an excellent radio telescope, providing data for Nobel Prize winning research into pulsars and gravitational waves and many other projects. Arecibo Observatory Aerial View

The telescope was designed to look mostly straight up, so the main reflector dish was built into a sinkhole and is not movable like most telescopes. An observing platform was suspended above the reflector dish by 5 cables connected to each of three massive concrete towers. The cables allowed for some amount of movability to the observing platform, which allowed Arecibo to observe different parts of the sky.

Recently, the telescope was damaged by several hurricanes, causing one instrument built for studying the ionosphere to fall off of the observing platform. In August 2020, one of the cables holding up the observing platform broke and repair work began to replace the broken cable. However on November 7, 2020, another cable on the same tower broke, leaving only three cables on that tower. It then became clear that the cables were in much worse shape than expected, leaving open the possibility for more to break at any time. These cables are huge---around 4 inches in diameter and made of steel---so when one breaks, it releases a tremendous amount of stress and the cable goes whipping through the air. You don't want anyone to be nearby when that happens! So the facility was evacuated, and several engineering firms did a detailed analysis and found that there was no path to repair the facility. On December 1, 2020, the final cables supporting the observing platform failed, and the platform collapsed into the ground. On the bright side, nobody was reported hurt, but it was a sad day for the astronomy community.

An image of Arecibo before and after its observing platform collapsed. Courtesy Deborah Martorell,

To me, the saddest part was that all the equipment on the observing platform was destroyed. But there are plenty of other reasons that I would've liked to see Arecibo continue on, including the fact that at the time of its collapse, it was still one of the most sensitive radio telescopes in the world, and it was one of the only telescopes capabale of mapping asteroids with radar. It was also iconic as the set for the James Bond movie Goldeneye, and just an all-around cool-looking telescope.

There is one other facility in the world with capabilities similar to those of Arecibo, and that is the FAST telescope in China, which is slightly bigger and has some cool features like being able to change the shape of the dish slightly on the fly. I hope that it will be able to carry on Arecibo's legacy of discovering pulsars and fast radio bursts, and continue advancing the frontiers of science.

This article was updated on December 1, 2020 to reflect the fact that the telescope collapsed.

About the Author

Christopher Rooney

Christopher Rooney

Christopher Rooney is a second-year grad student at Cornell and currently editor-in-chief of Curious (meaning that anything wrong on the website is his fault). Christopher studies galaxies far, far away trying to find the galaxy where Star Wars took place trying to characterize star-formation at a time in the history of the Universe when stars were being formed extremely quickly. He also works on the detectors used to measure the light from these galaxies.

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