Closing the windows on the cosmos

Through interviews and email exchanges with dozens of researchers, administrators, press officers and observatory directors, as well as reviewing a private list circulating among scientists, Astronomy magazine has confirmed more than 120 of Earth's largest telescopes are now closed as a result of COVID-19.

Many of the shutdowns happened in late March, as astronomy-rich states like Arizona, Hawaii and California issued stay-at-home orders. Nine of the 10 largest optical telescopes in North America are now closed. In Chile, an epicenter of observing, the government placed the entire country under a strict lockdown, shuttering dozens of telescopes. Spain and Italy, two European nations with rich astronomical communities — and a large number of COVID-19 infections — closed their observatories weeks ago.

Even many small telescopes have now closed, as all-out shutdowns were ordered on mountaintops ranging from Hawaii's Mauna Kea to the Chilean Atacama to the Spanish Canary Islands. Science historians say nothing like this has happened in the modern era of astronomy. Even during the chaos of World War II, telescopes kept observing.

As wartime fears gripped Americans in the 1940s, German-born astronomer Walter Baade was placed under virtual house arrest. As a result, he famously declared Mount Wilson Observatory in California to be his official residence. With the lights of Los Angeles dimmed to avoid enemy bombs, Baade operated the world’s largest telescope in isolation, making groundbreaking discoveries about the cosmos. Among them, Baade’s work revealed multiple populations of stars, which led him to realize that the universe was twice as big as previously thought.

In the decades since, astronomers have built ever-larger telescopes to see fainter and farther-off objects. Instruments have become increasingly complex and specialized, often requiring them to be swapped out multiple times in a single night. Enormous telescope mirrors need regular maintenance. All of this means observatory crews sometimes require dozens of people, ranging from engineers and technicians to observers and astronomers. Most researchers also still physically travel to a telescope to observe, taking them to far-flung places. As a result, major observatories can be like small villages, complete with hotel-style accommodations, cooks and medics.

But although observatories might be remote, few can safely operate during a pandemic.

“Most of our telescopes still work in classical mode. We do have some remote options, but the large fraction of our astronomers still go to the telescopes,” says Mulchaey, who also oversees Las Campanas Observatory in Chile and its Magellan Telescopes. “It’s not as automated as you might think.”

‘You don’t know what you missed’

Some of the most complicated scientific instruments on Earth are the gravitational-wave detectors, which pick up almost imperceptible ripples in space-time created when two massive objects merge. In 2015, the first gravitational-wave detection opened up an entirely new way for astronomers to study the universe. And since then, astronomers have confirmed dozens of these events.

The most well-known facilities, the twin Laser Interferometer Gravitational-wave Observatory (LIGO) — located in Washington state and Louisiana, both pandemic hot spots — closed on March 27. Virgo, their Italian partner observatory, shut down the same day. (It’s also located near the epicenter of that country’s COVID-19 pandemic.)

More than 1,200 scientists from 18 countries are involved with LIGO. And no other instruments are sensitive enough to detect gravitational waves from colliding black holes and neutron stars like LIGO and Virgo can. Fortunately, the observatories were already near the end of the third observing run, which was set to end April 30.

“You don't know what you missed,” says LIGO spokesperson Patrick Brady, an astrophysicist at the University of Wisconsin-Milwaukee. “We were detecting a binary black hole collision once a week. So, on average, we missed four. But we don't know how special they would have been.”

The gravitational-wave detectors will now undergo upgrades that will take them offline through at least late 2021 or early 2022. But the pandemic has already delayed preliminary testing for their planned fourth run. And it could prevent future work or even disrupt supply chains, Brady says. So, although it’s still too early to know for sure, astronomy will likely have to wait a couple of years for new gravitational-wave discoveries.

Then there's the Event Horizon Telescope (EHT). Last year, the EHT collaboration released the first-ever image of a black hole. And on April 7, they published another unprecedented image that stares down a black hole's jet in a galaxy located some 5 billion light-years away. But now, EHT has cancelled its entire observing run for the year — it can only collect data in March and April — due to closures at its partner instruments.

Around the world, only a handful of large optical telescopes remain open.

The Green Bank Observatory, Earth’s largest steerable radio telescope, is still searching for extraterrestrial intelligence, observing everything from galaxies to gas clouds.

The twin Pan-STARRS telescopes on the summit of Hawaii's Haleakala volcano are still scouting the sky for dangerous incoming asteroids. Both instruments can run without having multiple humans in the same building.

“We are an essential service, funded by NASA, to help protect the Earth from (an) asteroid impact,” says Ken Chambers, director of the Pan-STARRS Observatories in Hawaii. “We will continue that mission as long as we can do so without putting people or equipment at risk.”