There are more than 100 known planets around other stars, and astronomers tell us there are billions. Some are cold. Some are hot. Some are stable. Some are doomed. Many are like Jupiter. Others are so large they stretch the very definition of planethood. Future discoveries will almost surely yield rocky planets like Earth.

Astronomers detect these faraway places by noting a gravitational wobble in the star, or by the chance passage of the planet in front of its star, causing a tiny dip in the amount of starlight that reaches Earth.

Yet so far all of these extrasolar worlds are known through limited data and by their shadows. We "see" them only through artists' eyes.

The artists also interpret sketchy data collected on nascent solar systems, where worlds are presently forming around newborn stars in setups destined to look a lot like the nine-planet configuration we're familiar with.

Many artistic impressions of other worlds are rooted solid scientific data. Others are more imaginative but no less plausible given the current lack of knowledge about the universe beyond our little corner of it. Here are some of the best examples:

In 1997, astronomers found some stars that had been tossed out of their home galaxy, left to wander through intergalactic space. Imagine living on a planet around such a star -- there would be no starry night sky!

In this illustration, by James Gitlin, galaxies in the Virgo Cluster are dimly visible from a hypothetical planet around one of the outcast stars.