The Earth is special to us – it’s our home. But is it really special as a planet? Every star we can see in the night sky is likely to be orbited by planets. There are probably a thousand billion planets in our galaxy alone.
In about twenty years, over 4700 “exoplanets” have been discovered in distant solar systems. There are planets completing a revolution around their mother star in less than one day, as well as planets orbiting two or even three stars or moving on trajectories so eccentric as to resemble comets. Some of them are freezing cold, some are so hot that their surface is molten. But beyond that our knowledge falters: What are they made of? How did they form? What’s the weather like there? Are they habitable?
A suite of space missions are currently in operation or will be launched within this decade to discover more exciting planets and unveil their nature. Finding out why are these new worlds as they are and what is the Earth’s place in our galaxy and –ultimately– in the universe, is one of the key challenges of modern astrophysics.