美国国家公共电台 NPR Out Of This World: How Artists Imagine Planets Yet Unseen（在线收听）

Out Of This World: How Artists Imagine Planets Yet Unseen

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It seems like almost every week scientists announce that they have detected a new planet orbiting some distant star. The news is usually released along with an artist's impression of what that planet might look like. NPR's Nell Greenfieldboyce wondered how much freedom those artists get to create their visions of alien worlds.

NELL GREENFIELDBOYCE, BYLINE: When it comes to our own solar system, we've got tons of drop-dead-gorgeous photos - red canyons on Mars, the rings of Saturn, the ice on Pluto. The planets outside our solar system are a different story. Over the last two decades, scientists have discovered thousands of them, but not by actually seeing them. What they see is how a planet's gravity tugs on its star or how a planet blocks a star's light.

TIM PYLE: Did that star slightly move a little - kind of wobble left and right? Or did the brightness of the star dim just a little bit?

GREENFIELDBOYCE: That's Tim Pyle. He's a graphic artist who works at NASA's Spitzer Science Center at Cal Tech. He says, by looking at the star...

PYLE: We're actually able to extrapolate quite a bit of information about, say, the number of planets that might be around it, their distance from the star, their size.

GREENFIELDBOYCE: Still, that leaves a lot of details that have to be filled in if you want to create a plausible picture of what the planet might look like. And that's Pyle's job. He's illustrated dozens of planet discoveries and tries to tell a visual story about each world.

PYLE: If, you know, we find a planet that potentially has liquid water on its surface - and let's say that's pretty rare - you're going to make sure that, whatever your artist's concept is, you're focusing on that water in some way.

GREENFIELDBOYCE: But it gets complicated. Take a planet called Kepler-186f, a rocky planet that might have liquid water or maybe not.

PYLE: So we didn't want the general public to see this artist concept and walk away thinking, wow, they found another Earth. So a detail as small as what color is the water that I'm illustrating on the surface of the planet ended up becoming a really big thing.

GREENFIELDBOYCE: The water's color got tweaked again and again.

PYLE: Because we wanted it to be clear that it's water, but we certainly didn't want it to look, say, blue because that would look inviting, like, oh, wow, I want to go to Kepler-186 and dive into the water and swim around. It looks awesome.

GREENFIELDBOYCE: They settled on a kind of muddy brown. Then there was the time he illustrated Kepler-452b. Scientists couldn't agree on whether this planet could have water. It might have lost it all in what's called a runaway greenhouse effect. So Pyle created a planet that was just beginning to lose its water.

PYLE: So you can see lakes and rivers that have dried up and left behind salty residue along their shores. And it was kind of a green, ugly water, volcanoes all over the surface.

GREENFIELDBOYCE: Images like this get a lot of press attention.

PYLE: Which impressed my mom. It was on the cover of USA Today, and my mom actually saved a copy and sent me a copy.

GREENFIELDBOYCE: And creating these pictures has become a bit of a cottage industry. Pyle used to do computer graphics work in Hollywood, but now he collaborates with scientists, as well as another visual artist named Robert Hurt, who was trained as an astronomer. Hurt says, when illustrating a planet, there is one thing they never do.

ROBERT HURT: We have never put anything indicating the possibility of life or anything that you would look at and say, oh, yeah, that's definitely a living organism - trees, even algae, right?

GREENFIELDBOYCE: Even so, some people worry that these illustrations might give the public the wrong idea. Ray Villard is news director for the Space Telescope Science Institute.

RAY VILLARD: It's tricky with computer graphics. You can make stuff in such extraordinary detail. People might think it's real. People might think we've actually seen these features - canyons and all kinds of lakes and rivers.

GREENFIELDBOYCE: That's why he prefers illustrations that leave more to the imagination.

VILLARD: It can be evocative without showing every little rock and stone and cliff that's on the planet.

GREENFIELDBOYCE: Still, he doesn't want to knock the more photorealistic ones. He understands the need to excite and inspire the public. And given the technical challenges, he thinks it will be well into the next century until we can take a real photograph of a planet beyond our solar system that comes anywhere close to what a space artist can imagine. Nell Greenfieldboyce, NPR News.