Today's instruments have too little resolution to detect details found in some images, including moons, rings and volcanic activity. Cook takes her cue from astronomers when deciding how or whether to depict such enhancements. "Most of them are really pretty open to show what might be there," she says.
Robert Hurt, a self-described visualization scientist for the Spitzer Space Telescope, says he ups the realism of his depictions of distant gaseous planets by matching the size and shape of their roiling clouds with those of known solar gas giants.
Marcy says the artists he works with (including Cook) typically develop two drafts of an image before creating the final masterpiece [click here for examples]. Of course, he doesn't always have final say on the illustration that accompanies press releases. When his team discovered the first Saturn-like exoplanet, for instance, NASA commissioned an image of a reddish gas giant covered in white spiral clouds.
"This makes me cringe," he says. "It looked like the planet was wearing paisley pajamas." But it was out of his hands. "There's not much you can do when NASA says they want a [certain] depiction. You can't stop them."
Some observers say that an emphasis on realism might be a touch deceptive. "My problem with so much of the beautiful stuff that artists do is that we are not privy to the decision-making process," says Felice Frankel, a senior research fellow and science photographer at Harvard University. "The more, quote, 'real' something looks, the more you accept it as fact."
For Frankel, labeling something an artist's rendering is not enough, because an image leaves a lasting impression. She advocates literally showing viewers where the interpretation lies by providing multiple possible views—something Marcy and Cook have tried—or making images sketchier and more interactive.
"My fantasy is, for example, that you see a picture online and, with your cursor, you kind of travel around the artist's concept and you see a rollover of information," she says. "Why not say right at that spot, 'this is supposed to represent this but we're not sure about that and this and that'?"
Nobody disagrees that colorful, detailed images may carry a risk of misconception. But for the image makers—tasked by funding agencies to convey new findings to the public—the benefits outweigh the risk.
"It's alright to have pictures as long as they generate intelligent discussion," Marcy says. "Pictures allow people to imagine, where otherwise their imaginations might be somewhat limited."
Capturing a true image of an exoplanet, Marcy says, may have to wait until NASA scrapes together the money to launch the proposed Terrestrial Planet Finder, which would include a telescope equipped with a tool for blotting out distant stars, thereby creating an artificial eclipse to reveal orbiting planets.
Until then, the problem of realism versus abstract renderings has no easy solution, Hurt says, noting that the goal generally dictates the answer. "If a casual observer notices an artist's concept of a planet in an article in USA Today, [and] thinks 'wow, we're observing planets,' and [then] turns to the sports page, was that a success?" he asks.
Probably so, in his view. "If the image was dull or diagrammatic," Hurt says, "he might not have even noticed the article at all."
* Note: Exo-sticklers may recall that telescopes did image a planet-size red object around the brown dwarf 2M1207, but researchers do not believe it formed like the planets in our solar system did.