Broken cable damages giant Arecibo telescope

It has long been the largest radio telescope in the world and it is undoubtedly the most famous: we saw it in Contact with Jodie Foster, in X-Files and in GoldenEye, and even in a game setting Battlefield. It was with him that in 1974, we sent a message to aliens representing a human and the composition of his DNA. The Arecibo telescope is a star of popular culture in addition to being a star in astronomy. But today it is broken.

“One of the auxiliary cables that helped support the metal platform above the telescope broke on Monday, causing a 30-meter cut in the antenna.” spherical, reports the University of Central Florida (UCF), which manages the telescope. Installed on the island of Puerto Rico, the gigantic telescope is made up of a dish-shaped antenna 305 meters in diameter, and instruments suspended 150 meters above by cables. The plate reflects the waves coming from the universe and concentrates them towards the suspended receivers.

The Arecibo observatory in 2008. Photo JidoBG, CC BY SA

Exposed to the elements, the structure is necessarily fragile: in September 2017, the winds of hurricane Maria broke the large pointed antenna which fell puncturing the plate. The repairs were still not finished, recalls the UCF.

The radio telescope in 2019. On the left on the suspended platform, pointing down, the remainder of the long antenna broken by the hurricane in 2017. Photo Mariordo, CC BY SA

But this time there was neither a storm nor an earthquake. Why did this cable, with a section of 7 centimeters, fail? “A team of experts is assessing the situation, ensures the director of the observatory, Francisco Cordova. Our priority is to ensure the safety of the team, to protect the facility and to allow a return to operations as soon as possible, to continue to help scientists around the world. ” Any observation of the sky is of course suspended for the moment.

The hole caused in the plate of the Arecibo telescope by the rupture of a cable, August 10, 2020. Photo Phil Perillat

This other photo of the damage by researcher Phil Perillat better shows the extent of the hole in the giant plate, and the white cable which now hangs vertically. The size of the hole is not the most problematic, remarks astronomer Joe Swiggum : it only reduces the wave collection surface a little, making the telescope a little less sensitive. But the position of the hole also influences: as the note physicist Ale Pacini, it will be harder to observe certain ranges of wavelengths. And then “The collection area is just one problem among many. The Arecibo Observatory is designed to point positions in the sky to within a thousandth of a degree. Pointing accuracy relies on the balancing of a massive platform, suspended with… cables. ” We will have to make a complete assessment of the state of the observatory before resuming operations. A priori, the hanging dome which focuses the waves has also been slashed and the metal platform itself is twisted.

Normally, applications flow to Arecibo: many teams of researchers wanting to take advantage of the power of the radio telescope argue the scientific interest of their respective projects to obtain “observation time” – that is, say the reservation of a slot. We can use Arecibo to observe the planets of the solar system on radar, to “listen” to pulsars where the rapid radio bursts… We still do not know the origin of these mysterious radio signals, but the Arecibo telescope discovered in 2016 the first recurring source of rapid radio bursts.

Camille Gevaudan

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