Generally speaking, exoplanets can be any size, and they are found in a wide range of orbits. Some have massive gas atmospheres; others are smaller with an icy or rocky composition.

One of the first thoughts I had, when doing early exoplanet research, was that Earth and its many companions seemed very different from the planetary systems we were detecting.

In 1999, my team discovered that the star Upsilon Andromedae was circled by three gas-giant planets - the first distant multiplanet system ever found. That same year, other researchers observed the first 'transit' of an exoplanet - a planet blocking out a small fraction of the starlight as it passes in front of the star.

The first exoplanet to be found around a sun-like star was discovered in 1995, just two years before I began studying exoplanet detection.

I hope that vigorous space exploration continues and that humankind will have a space station that resides between Earth and the moon. Outside the gravitational field of Earth, we could launch robotic spacecraft to other destinations in our solar system.

Further ahead, I'd like to see tiny spacebots - smaller than your cell phone - travel outside our solar system to the nearest star system, Alpha Centauri. By keeping the mass of those spacebots low, we could more easily accelerate them.