The legendary Arecibo telescope will close forever – scientists are wavering

One of the most famous telescopes in astronomy – the 305-meter-wide radio telescope in Arecibo, Puerto Rico – is permanently closing. Engineers can’t find a safe way to fix it after two cables supporting the structure suddenly and catastrophically broke, one in August and one in early November.

It is the end of one of the most iconic and scientifically productive telescopes in the history of astronomy – and scientists mourn its loss.

“I don’t know what to say,” says Robert Kerr, former observatory director. “It’s just incredible.”

“I’m totally devastated,” says Abel Mendéz, an astrobiologist at the University of Puerto Rico at Arecibo who uses the observatory.

The Arecibo telescope, built in 1963, was the largest radio telescope in the world for decades and has historical and modern significance in astronomy. It was the site from which astronomers sent an interstellar radio message in 1974, in case extraterrestrials could hear it, and where the first known exoplanet was discovered, in 1992. It has also done pioneering work in detecting nearby asteroids. to Earth, observing the bewildering celestial bursts known as fast radio bursts and studying many other phenomena. All of these lines of investigation are now permanently closed, although limited science continues in some smaller facilities at the Arecibo site.

Assess the damage

The broken cables helped to support a 900-tonne scientific instrument platform, which hangs over the telescope’s main dish. The first cable shattered the panels on the edge of the dish, but the second tore huge cuts in a central part of it. A high resolution satellite image, produced at NatureThe request from Planet, an Earth observation company, shows the extent of the damage caused by the second cable; the green of the vegetation below can be seen through large holes in the plate. A second photograph, released this week by observatory officials, also reveals the destruction. They are the only public glimpses of the damage to date.

If other cables fail, which could happen at any time, the entire platform could crash into the dish below. The US National Science Foundation (NSF), owner of the Arecibo Observatory, is working on plans to safely lower the platform in a controlled manner.

But these plans will take weeks to develop, and it is unknown if the platform could crash uncontrollably in the meantime. “Even attempts to stabilize or test the cables could lead to accelerating the catastrophic failure,” said Ralph Gaume, chief of astronomy at the NSF, at a news conference on November 19.

So NSF decided to permanently close the Arecibo pot. “This decision is not an easy one to make, but safety is the number one priority,” said Sean Jones, chief of mathematics and physical sciences at the NSF.

The closure will likely come as a shock to the wider astronomical community. “The loss of the Arecibo Observatory would be a great loss for science, for planetary defense and for Puerto Rico,” said Desireé Cotto-Figueroa, astronomer at the University of Puerto Rico in Humacao, in an email before the closure announced.

NSF officials insist the cable failures came as a surprise. After the first, the engineering teams spotted a handful of broken wires on the second cable, which was more crucial to supporting the structure, but they didn’t see it as a big deal because the weight it carried was within its design capability. “It was not seen as an immediate threat,” says Ashley Zauderer, Arecibo program manager at NSF.

Over the years, external review committees have highlighted the continuing need to keep the telescope’s obsolete cables. Zauderer said maintenance was completed on schedule.

Prior to this year, the observatory’s last major cable problems occurred in January 2014, when a magnitude 6.4 earthquake caused damage to another of the main cables, which engineers repaired. The aging facility has suffered other shocks in recent years, including Hurricane Maria in 2017 and a series of small earthquakes in January of this year.

There are still no estimates on the cost of decommissioning the telescope.

A legendary site

Some of the observatory’s science projects could be transferred to other facilities, Gaume said – and he expects scientists to suggest where to move their research. The science continues in other parts of the Arecibo observatory, which encompasses more than the 305-meter parabola. They include two lidar structures that fire lasers into the atmosphere to study atmospheric phenomena.

Arecibo had been regularly updated, with several new tools expected to be installed in the coming years. “The telescope is in no way obsolete,” says Christopher Salter, an astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, who has worked at Arecibo for years.

The observatory is also a major science-educational center for Puerto Rico, promoting the careers of many astronomers and engineers. And it has become part of the pop culture lexicon, featured in major films like Contact, based on a Carl Sagan novel and the James Bond film Golden eye.

The last major radio telescope disaster occurred in 1988, when a 300-foot-wide antenna at the Green Bank Observatory, West Virginia, collapsed one night due to structural failure.