Destroyed, Arecibo telescope not to be rebuilt

In December 2020, when the massive Arecibo Observatory in Puerto Rico collapsed, a hole was opened in astronomy.

For half a century, Arecibo was the most powerful telescope on the planet. At 305 meters wide, it listened to radio signals coming from stars — and from pulsars, planets, asteroids and other bodies — to try to detect any hints of intelligent life or objects that could potentially destroy Earth, as well as gain insights into the mysteries of Earth. gravity and space-time.

The disappearance of the Arecibo telescope also blew a hole in Puerto Rico’s pride and economy, repeatedly hit by hurricanes, earthquakes and widespread electrical blackouts. Since 1963, when the telescope was founded, generations of Puerto Rican schoolchildren have walked the hills to arrive at a science-fiction scenario: a giant concave antenna set up like a giant bowl in a mountain valley, with 900 tons of radio receivers suspended above Is it over there.

There, teenage students could stand alongside renowned scientists at work and be inspired by science, especially astronomy. Many of them ended up becoming astronomers themselves.

These visits will continue, in a way. Last month, the National Science Foundation (NSF), which owns the Arecibo Observatory, announced that it will spend $5 million to create a world-class educational center there. The Arecibo Center for STEM Education and Research will include the Ángel Ramos Scientific and Visitor Center, as well as an exhibition space, laboratory, office space, dormitories, auditorium and cafeteria.

The only thing that will not be present is the telescope. In a statement it issued last month asking for proposals from researchers interested in doing projects at the site, the NSF said the plan “does not provide for the reconstruction of the 305-meter telescope or the Lidar facility.”

Astronomer Dan Werthimer of the University of California at Berkeley has used the telescope throughout his career to search for radio signals from extraterrestrial civilizations and regretted the decision not to reconstruct it. “Of all the telescopes in the universe, Arecibo was my favorite,” he commented.

“This is a sad time for the Puerto Rican people. The Arecibo telescope was a source of pride and joy for him.”

A sense of loss spread through the astronomical community.

“When NSF announced that it intends to convert the site primarily into a science, technology, engineering and math education center and end almost all scientific effort, it came as a shock,” University of Vermont radio astronomer Joanna Rankin wrote in an email. member of a group of 400 astronomers known as the Science Defense Partnership at Arecibo. “Many of us who have used the instrument and know its many qualities were dismayed by this unexpected decision.”

A headline in The Register, a daily online publication covering technology, complained that the NSF intends to replace the telescope with a school.

The Arecibo Observatory, officially titled the National Center for Astronomy and Ionosphere, was originally built as an interplanetary radar and radio telescope to study, among other things, the properties of objects such as warheads that fall into the atmosphere. Over the years it has been seen as a symbol of human curiosity and cosmic optimism. The observatory appeared in the movie “Contact”, in which Jodie Foster plays an astronomer who discovers a communication signal coming from space, and in “007 vs. Goldeneye”, in which it is the lair of a supervillain enemy of James Bond.

The telescope helped radio astronomers win a Nobel in physics for their observations of a pair of pulsars emitting gravitational waves, the ripples in space-time predicted by Albert Einstein. And it was part of a new NASA planetary defense initiative, tracking and deflecting radar from potentially lethal asteroids.

Over time, however, the shrinking budget and insufficient maintenance had consequences.

In November 2020, a cable holding the 900-ton platform of airborne radio receivers over the dish broke, leaving the instruments dangling dangerously. The NSF started making plans to shut down the telescope, but nature got ahead of it. On the morning of December 1, 2020, the remaining cables broke and the platform collapsed, demolishing the dish and everything around it.

Many astronomers were devastated. But science is resilient. Before the final collapse took place, scientists had mobilized to plan how to rebuild or replace the much-loved telescope.

Their efforts yielded a paper describing what its 70 or so authors dubbed the Next-Generation Arecibo Telescope, or NGAT. The paper was presented to the National Academy of Sciences as part of a survey of astronomical priorities for the next decade.

Recently, China has built an even larger radio telescope, the Spherical Radio Telescope with 500 Meters Aperture, or Fast. But the use of giant dishes has gone out of fashion in radio astronomy, giving way to much smaller dish sets capable of harvesting the same amount of radio energy, but in a more versatile way. The NGAT team designed 1,112 antennas, each nine meters long, onto a giant mobile platform or set of platforms that could tilt or turn to point in far more directions in the sky than the original Arecibo antenna, which was fixed to the ground. and limited as to the distance from the celestial zenith to which it could aim.

The NGAT proposal came with a list of topics that could be studied if the telescope is rebuilt: pulsars around the ultra-large black hole at the heart of the Milky Way; molecules in the early universe; space junk and space weather, dark energy, dark matter and much more.

“These capabilities will tremendously increase the site’s user base and enable cutting-edge scientific work for decades to come,” wrote the authors of the proposal, led by Anish Roshi, senior scientist at the Arecibo Observatory.

Radio astronomers admit that the ideal location for a telescope like the one being proposed by the NGAT team would be high-altitude and dry, situated in a desert rather than in the humid, rainy mountains of Puerto Rico. But the moral debt to Puerto Rico speaks louder.

The project’s anticipated price tag would be $454 million, a hefty sum for the NSF, which is also receiving orders to invest billions in gravitational wave detectors, a pair of giant ground-based optical telescopes and other ambitious projects that would help American scientists keep track of the future. rest of the world.

In statements given to the Associated Press, an NSF representative said the government already has other instruments that can handle some of the tasks that were done by the old telescope.

Rosh said in an email that astronomers loved the idea of ​​a science, technology, engineering and math center in Arecibo, but questioned whether it would make sense to create one on site without being accompanied by a research facility.

“In my opinion, the observatory and the wider scientific community should take this opportunity to step up the telescope reconstruction effort and avoid destroying the observatory and other research activities being carried out today in Arecibo,” Roshi said.

But it is possible that this moment marks the end of an era. The announcement of the telescope’s demise came just a month after the death of astronomer Frank Drake, who used Arecibo to search for extraterrestrial signals and in 1974 requested it to transmit a historic radio message into space.

Cosmic optimism and boldness require money and cables. And no good idea, whether a robot on Mars or a telescope in space, can survive without maintenance.

^{Translation by Clara Allain}