美国国家公共电台 NPR Chile And Telescopes Are A Match Made In Heaven（在线收听）

ARI SHAPIRO, HOST:

The Atacama Desert in Chile is one of the driest places in the world. And dry is good for radio telescopes because it lets them see the heavens more clearly. NPR science correspondent Joe Palca reports on an array of some five dozen radio telescopes that provide a unique view of the universe.

JOE PALCA, BYLINE: The telescopes look like large, steerable satellite dishes. They're in a part of the desert that's 16,000 feet above sea level.

This is just such a strange place because you're sort of standing in the middle of a high plateau. There's some rolling ridges off around the side, and dotting all over the landscape are these radio telescopes.

Dotting is the word because these radio dishes aren't all packed together. Any two of them can be as much as 10 miles apart. The thin air makes it hard for humans to work at 16,000 feet, so ALMA's main control room is at a lower altitude - a mere 9,500 feet above sea level. The day I visited, Ignacio Toledo was the astronomer on duty.

IGNACIO TOLEDO: In the control room, what we do is to operate the telescope, the ALMA observatory.

PALCA: Operating the telescope means deciding what the dishes are pointing at and monitoring atmospheric conditions, especially the amount of water vapor. ALMA can see radiation coming from things like dust and gas, but water vapor acts like a cloud, blocking the signal.

TOLEDO: The lower the value, the better the observations, and right now, it's pretty good.

PALCA: ALMA is very popular with astronomers. Toledo says more want to use it than the facility can accommodate.

TOLEDO: In total, they were requesting around 16,000 hours. And we can only give 4,000, so they do a selection based on the scientific merits of the project.

PALCA: On the day I visited, the telescope was pointing at an object an astronomer named David Principe wanted to study. Toledo told me Principe would receive an email letting him know his turn had come up. So when I got back to my desk at NPR HQ, I checked in with Principe.

DAVID PRINCIPE: I was sitting on a beach in Nantucket, and I got the email. And I was surprised because my cell phone had very little reception.

PALCA: He was at the beach because his observing time happened to fall on the Fourth of July. Principe uses ALMA to study star formation.

PRINCIPE: The earliest stages of a star's life.

PALCA: In those early stages, the star is surrounded by a thick ring of dust, something that ALMA is particularly good at seeing.

PRINCIPE: And this ring is ultimately where planets are forming.

PALCA: You can't actually see the planet, but you can see a gap in the ring where the planet's gravity has cleared away the material. Like almost all of ALMA's users, Principe didn't travel to the observatory when his measurements were being made. At some point, he'll receive a large data file containing his results that he can study in a computer in his office. ALMA astronomer Ignacio Toledo says this remote capability takes some of the magic out of observing with a telescope.

TOLEDO: It's less romantic, yes. But at least for me, and I think for most of the people here, they work in this feeling that what we're doing is something awesome.

PALCA: Learning how the universe is put together does have an awesome component to it.

Joe Palca, NPR News.

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