Birds and other complications of celestial scientific work with telescopes

Few things in science appear to be as precarious as the giant mirrors in modern telescopes. These mirrors—meters in diameter, tons in weight, and costing millions of dollars—are polished to the precision of a fraction of a wavelength of visible light to the concavity required to capture starlight.

When they are not working, they are sheltered in domes that protect them from the distortions of humidity, wind and temperature changes.

But this cannot protect them from all the vicissitudes of nature and humanity, as I was able to verify in a visit to the Las Campanas Observatory, in Chile.

Looking into one of the telescope’s mirrors—20 feet of immaculately curved, shiny glass—I noticed a small, suspicious speck. It looked like the kind of stain you might find on your car windshield.

“Birds,” one astronomer whined when I asked him about it.

It happens frequently, said others. But it’s not just birds that can stain a mirror. Mike Brotherton, director of the Wyoming Infrared Observatory, posted a photo on Facebook of the frost that had accumulated on his mirror while the dome was open. “It’s hard to keep a mirror spotless,” he said. “It’s a balance between opening up to collect data and protecting the mirror.”

Last fall, the 8-meter-diameter main mirror of the Gemini North telescope in Hawaii suffered a chip on its outer edge while being moved for cleaning and coating. It was successfully repaired.

Some things are less easy to fix. In 1970, a worker at the McDonald Observatory in West Texas brought a gun to work and opened fire, first at his boss and then at the main mirror of a new 9-foot reflecting telescope. He then he used a hammer.

No one was injured during the attack. And apart from seven small bullet holes, which affected only about 1 percent of the mirror’s surface area, the telescope was largely unscathed.

The most famous example of what can go wrong with a mirror occurred in 1990, when the Hubble Space Telescope was launched with a misshapen mirror that couldn’t focus. The astronauts were able to fix it, and Hubble continues with its work. But the episode led NASA to be more cautious with Hubble’s successor, the James Webb Space Telescope.

The Webb was successfully launched on December 25, 2021, but space is also a shooting range. The telescope was soon struck by a micrometeorite, which left a tiny crater in one of the telescope’s mirror segments. Since then, NASA has minimized the amount of time the telescope is pointed at streams of meteors.

The cosmos has its ways to protect its secrets.

By: DENNIS OVERBYE