The Arecibo Telescope collapsed in early December 2020 after 57 years of observing the universe. Here's what the telescope accomplished and why its loss is a devastating blow to science.
At the end of what was already a tough year, in December of 2020 astronomers faced another loss, the collapse of the Arecibo Telescope. For 57 years the telescope observed the universe through radio eyes, but due to a mix of complicated engineering issues, politics, and a few snapped cables, the bulk of the telescope came crashing down one morning in December.
Although the telescope is a part of pop culture, its legacy is rooted in its science.
If you’ve seen the movie "Contact" with Jodie Foster or "GoldenEye" with Pierce Brosnan, you may recognize the Arecibo Observatory. It is such a unique place that it was also featured in an episode of the X-Files. But although the telescope is a part of pop culture, its legacy is rooted in its science. Let’s take a look at the important scientific contributions we owe to this incredibly unique observatory.
Where is the Arecibo Observatory?
The Observatory sits in a remote region in the Puerto Rican jungle. To get there, you must leave the bustling, culture-packed city of San Juan behind and drive two hours to where the terrain becomes very hilly. The karst or limestone-like topography covers the region with large sinkholes.
It’s hard to get a sense of just how huge this dish is from pictures.
Nestled in one of these gigantic sinkholes is an enormous dish spanning 305 meters (approximately 1,000 feet) across. It’s hard to get a sense of just how huge this dish is from pictures. Even up close, you can only see the whole thing from a perch high above from either the Observatory control room or the Angel Ramos Visitor’s Center. Until recently, the Arecibo dish was the largest single-dish telescope in the world with a size equivalent to a bit longer than three football fields or a bit shorter than three soccer fields.
What did the Arecibo Telescope do?
The Arecibo Telescope observes at radio wavelengths—that's light with wavelengths too long for our eyes to see. That means it can see things that traditional optical telescopes can’t. So, what emits at radio wavelengths?
Surveys conducted at the telescope have discovered entire galaxies never seen before.
When stars die, they leave behind very dense remnants that differ in makeup depending on how massive the star was when it first lit up. Stars on the smaller, less-massive end, like our Sun, will turn into white dwarfs. The largest, most massive stars will turn into black holes. The stars that fall somewhere in between become neutron stars, dense clumps of degenerate neutron matter that emit powerful beams of radiation. Those beams sweep across the sky as the neutron star rotates in the same way a lighthouse's beam does. If pointed at us, we observe those beams as pulses and call this subclass of neutron stars pulsars. Arecibo has found hundreds of these rapidly rotating pulsars, including a few that appear to mysteriously vanish right out of the sky.
Surveys conducted at the telescope have also discovered entire galaxies never seen before. Our Milky Way galaxy is a collection of hundreds of billions of stars like our Sun, all of which form out of clouds of gas and dust. We can use optical and infrared telescopes to observe that starlight. But not all galaxies are such prolific star formers, so we need to look for them via that gas and dust that hasn’t yet collapsed into a star.
Arecibo Telescope functions and my involvement
For my dissertation studies, I spent many months at the Arecibo Observatory conducting the ALFALFA survey, a blind sweep of a huge swath of the sky. We found thousands of new galaxies, investigated the nature of the high-velocity clouds that swirl around our own galaxy, and created a map that revealed the large-scale structure of the universe.
I spent many months at the Arecibo Observatory conducting the ALFALFA survey, a blind sweep of a huge swath of the sky.
The Arecibo Telescope also was home to the most powerful planetary radar system in existence. The radar system transmits (which is fancy-speak for "shoots out powerful beams of light"!) with a 1 MW transmitter at a frequency of 2380 MHz. Those radio wavelengths are sent into space and aimed at a nearby object like an asteroid, planet, or moon. That emission gets reflected and then recollected by the telescope to create a map of that object’s surface. This work is incredibly important for monitoring what we call Near Earth Asteroids, the asteroids that get close to our planet. Mapping and monitoring these NEAs allow us to compute their trajectories with more precision and gauge the likelihood of a possible future encounter.
Scientists even used Arecibo to send a message in the 1970s to any aliens that might be listening. The message was aimed at the star cluster M13 and was an attempt to encode the foundational aspects of what it’s like to live on Earth. Every year in my Astro 101 class I like to ask my students what information they would deem most important to give as a first impression of our planet.
Loss of the telescope
The first step in making all of these observations happens when the radio light that has traveled from across the universe hits the big dish that sits in the karst sinkhole. That light then gets reflected off the dish and sent into what we call “the Dome,” a four-story dome-shaped structure full of high-tech receivers. Those receivers then interpret the light so astronomers can decipher what kind of astronomical object emitted it.
The Dome, and the platform that supports it, weighs around 900 tons. (That's the equivalent of 300-400 SUVs.) All of this weight has to be suspended above the big dish by cables that extend out to three towers around the perimeter of the dish. If you instead had a large column or supporting pole that went directly to the ground, that structure would block light from reaching the telescope and thus hinder the astronomical observations.
In December, the four-story Dome and all of its receivers, each one a result of impressive engineering, came crashing down.
The 900-ton platform is suspended 500 feet in the air above the dish by only 18 cables. In August of 2020, one of those cables snapped. While the National Science Foundation, the organization charged with funding the maintenance of the telescope, arranged for engineers to address the first snapped cable, a second snapped in early November.
As you can imagine, when you only have 18 cables holding up 900 tons, losing two of those cables is a recipe for disaster if not addressed swiftly. Unfortunately, a disaster is what happened in December when the remaining cables eventually gave up and the entire platform, including the four-story Dome and all of its receivers, each one a result of impressive engineering, came crashing down.
As an astronomer who has spent many months at the Arecibo Observatory and years analyzing its data, it's hard to describe what it means to lose this telescope. Watching the platform and the Dome fall is much like watching my dreams crash out of the sky. When I first started to pursue a career in astrophysics research as a new Ph.D. student, I was only 22 so being entrusted with such an important and powerful instrument was life-changing for me. It is not an exaggeration to say I would not be a scientist without it.
As an astronomer who has spent many months at the Arecibo Observatory and years analyzing its data, it's hard to describe what it means to lose this telescope.
The Observatory has also been an important resource for Puerto Rican astronomers who have led many of the important studies conducted there. Hispanic people are largely minoritized in STEM fields, making up 16% of the US workforce but only 7% of all STEM workers. To learn more about the work of Puerto Rican astronomers and what the telescope has meant for their careers, check out the Twitter hashtag #WhatAreciboMeansToMe.
What's next for the Arecibo Telescope?
The events that allowed the collapse to happen are complex, but it was far from inevitable. A large part of the problem is likely rooted in the fact that Puerto Rico has no representation in Congress. When a 300-foot radio telescope collapsed in West Virginia, it was Senator Robert Byrd who pushed for it to be rebuilt. Puerto Ricans do not have the same representation.
When the second cable snapped and the National Science Foundation announced that repairing the telescope was too dangerous, the group Puerto Ricans in STEM immediately started a petition to push for repairing the telescope. The petition gained more than 66,000 signatures in 2 weeks. Now there is a new petition to Congress to allocate funds to build a new and improved version of the telescope to carry on its work of finding pulsars, galaxies, and incoming asteroids.
I am so incredibly lucky to have been able to contribute to the legacy of this incredible telescope.
A fond farewell from me as your Ask Science host
And on the topic of legacies, my sign off for today’s episode will be my last as your Ask Science host. I am grateful to all of my listeners for the fantastic questions you've sent me and for the inspiring conversations we've had over the past six years.
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