The number of bizarre and familiar new worlds just waiting to be discovered is staggering, if estimates prove to be accurate. In our Milky Way alone there could be hundreds of billions of planets, and so far we've found just a few thousand. The ultimate goal for planet hunting is to find an Earth-analogous planet that could help ascertain whether life could potentially grab a foothold outside of our Solar System.
The key to discovering an Earth-like planet is to find those that are within the habitable or 'Goldilocks' zone of a star, the area within which the conditions are thought to be 'just right' for water to form. Kepler-22b was the first such planet to be found and, while it is now thought to have a thick atmosphere that may be inhospitable to life, it was very influential in helping to spur the discovery of new Earth-like planets. One example of these was Gliese 581 g, a planet no more than four times the mass of Earth sitting right in the middle of the habitable zone of its host red dwarf star. While a year on this planet is only 37 days, observations suggest that Gliese 581 g may be a suitable planet on which life could reside.
Another potentially life-harbouring planet is HD 85512 b, a so-called 'Super-Earth', like Gliese 581 g, with a mass at least 3.6 times that of our home planet but with a temperature that could potentially allow for the existence of liquid water, which is thought to be one of the key components for life to form or survive. Over the next few years, as our methods of finding and characterising exoplanets become more and more sophisticated, it's likely that more Earth-like planets like these will be discovered all over the Milky Way.