Superimposed image of the Milky Way and Australian Aboriginal engraving of 'The Emu In The Sky' (Barnaby Norris)

Scientific illustration has a long and noble history, from ancient depictions of celestial forms to Leonardo Da Vinci's extraordinary drawings of anatomy and invention, to the latest computer-generated animation splashed across CNN or - perhaps with more reflective thought - the cinematic screens of the world's great science museums. In English the word 'illustrate' has its origins with bringing fire, or light, to a subject, illuminating it. And I think this is often more appropriate, the best scientific illustration doesn't just depict, it also brings a luminescence, a life to the subject.

It's a tricky business though, because the moment an ancient life-form, or some impossible-to-see piece of physics is illustrated it can gain a personality that may be very misleading. But the risk is frequently worth it, scientists often desperately need a way to visualize their quarry, and a way to communicate their excitement to a wide and skeptical world. A gripping visual really can be worth a thousand words.

Two Laelaps a Leaping : from dry fossils to frisky dinosaurs (Charles R. Knight 1897)

A terrific example is the oft-cited work of Charles R. Knight in the late 1800's and first half of the 20th century, whose depictions of dinosaurs as living, breathing, flesh covered creatures helped revolutionize our intuitive feel for the deeply layered history of planet Earth. He had to tread a fine line though in re-animating what were in truth just dusty bones, and he didn't always adhere to the limits of scientific knowledge when a scene would look better with some extra vegetation or a more rambunctious Allosaurus.

In many respects we face a similar challenge with today's extraordinary exoplanet discoveries. Much like the mineralized fragments of a hundred million year old dinosaur, we have only a little information about the distant worlds now populating our surveys. But I think I speak for scientists as well as everyone else when I say that we ache to see these places with our own eyes, up close and personal. So what can be done? Is there a Charles R. Knight of the exoplanets, ready to illuminate these alien scenes?

Many months ago I got involved in a conversation with editor extraordinaire Amanda Moon about a new publishing project that aimed to do just this, not with paper and ink, but with the luminous screens of iPads and the work of Hugo-award winning artist Ron Miller and Scientific American's very own Ed Bell. The idea was to replace the usual expensive and static coffee table book with something new, part book, part app - a showcase of speculative imagination with a scientific basis. The resulting Journey to the Exoplanets is, I think, terrific but one of the most fascinating aspects is just how challenging it is to balance our limited knowledge with scientific extrapolation to make all this stuff actually interesting. Take for example the case of 16 Cygni Bb.

The orbit of planet 16 Cygni Bb compared to our solar system - it is highly eccentric

This is a gas-giant planet at least 68% more massive than Jupiter. It orbits a G-dwarf star not unlike our Sun, except likely a few billion years older. That star, some 70 light years from us, is also part of a hierarchical triple star system. Stars A and C (another G dwarf and a low mass M dwarf) form a binary and B - with its planet - orbits far outside this pair, taking at least 20,000 years to circumnavigate the others. The planet itself has a strongly eccentric, or elliptical orbit of about 800 Earth days in period. But this orbit suggests that for at least part of the time 16 Cygni Bb lies within the nominal habitable zone of the system.

However this is a gas-giant planet, so what is an artist to do to make this interesting, to provoke our senses and let us 'feel' what it might be like to be there? In this case the trick was to speculate that 16 Cygni Bb might harbor moons and that one of those moons could plausibly harbor an atmosphere and a close-to-habitable surface environment. As I've written about before, the idea of exomoons is not new, and is likely to become reality any day now.

The view of 16 Cygni Bb from one of its moons (Ron Miller)

So here is 16 Cygni Bb, seen not from its endlessly dull cloud tops but instead from a rocky outcrop above an undulating plain on the surface of one of its several moons. It's a dramatic and awe-inspiring sight. Is it real? We currently have no way of knowing, but it is certainly well within the range of possibilities.

For some of the known exoplanets Miller and Bell got even more ambitious - an iPad has motion and position sensors, so instead of displaying a single shot of an alien scene the screen can become a moveable window, placing you quite literally in the midst of another world. It's an unnerving feeling, being able to turn to check that nothing is creeping up on you from behind, Charles R. Knight would definitely have had a field day with this.

The other aspect of this kind of app-book hybrid that I think brings scientific illustration into a new regime is the possibility of endless updates. Exoplanets are being discovered at an ever increasing rate (almost exponentially in fact). So now a coffee table book or museum display becomes a source of news and a demonstration of the scientific process. Consider a system like the infamous Gliese 581 (where claims of genuinely habitable almost Earth-sized planets have come, and gone). These putative worlds can be shown, but the ongoing scientific story can also be told. Seeing them onscreen makes your heart ache for them to be real, and so if anything the fact that they may be mere figments of difficult data analysis makes us feel even more compelled to keep on searching.

A sampling of other worlds... (Ron Miller)

So by now you're wondering if this is just a long infomercial for the Scientific American imprint at Farrar, Straus and Giroux and my own part in the project - well, I guess yes and no (did I mention I got to do audio narration too?). I don't think I stand to get anything out of this, but I wanted to lead up to the part of Journey to the Exoplanets that I had the most hand in, and that I think offers a glimpse of one possible future direction for scientific illustration with benefits for both the layperson and for scientists - especially exoplanetary scientists.

Lurking in this app is a feature called 'Planet Builder', originating from Davide Castelvecchi's (Degrees of Freedom) fertile mind. The idea was simple, but getting it right was hard. What if the reader could themselves 'design' a planet? By choosing a stellar host, a planetary size, and properties like orbital distance and age they could create a three-dimensional representation of a scientifically accurate 'best guess' as to what such a world would look like. Suddenly the reader can themselves become a scientific illustrator - with the software acting as both guide and artist, making sure that whatever is produced is always within the bounds of plausibility. In this case, even with the amazing coding talents of Andrew Fox and the entire production team at Brandwidth, we faced the enormous restrictions of what still is (despite all gushing commentary) a small tablet computer. What was accomplished is I think great and I'm very proud of it, but it also demonstrates the potential for going even further.

What planet would you like today?

By incorporating a scientific model and then rendering this out as an image the illustration itself becomes flexible - viewable not just from different angles or with varying lighting, but with adjustable fundamental physical parameters. We can satisfy both our artistic eye and our scientific curiosity about the 'what if's?'

For exoplanetary science this may be incredibly important. Even the simple questions raised by trying to illustrate a scene like that on a hypothetical moon around 16 Cygni Bb (where would the moon be? How much light and radiation would it receive? How long would the day be?) challenge scientists to think things through to their logical conclusion, and possibly ask new questions that lead to new discoveries out in the real universe.

We'll have to wait and see how many future exoplanetary scientists admit that, just like so many paleontologists before them, their inspiration came from a glimpse into imagined worlds. My bet is it'll be a lot.