Extrasolar planets, often called exoplanets, are planets that exist in other solar systems other than our own. These planets are very hard to find and study because their light is fainter than the light given off by the stars which they orbit. In 1992, astronomers Aleksander Wolszczan and Dale Frail noticed several planets orbiting the pulsar PSR B1257+12. They only detected gas giants similar to Jupiter, leading to the hypothesis that gas giants are more common than terrestrial planets. This hypothesis has been disproven because of the fact that these gas planets were simply easier to detect because of their massive size.
Studying these extrasolar planets could bring us much more insight on how the Earth came to be and what changes we may potentially see in both our solar system and our planet. Perhaps there will even come a time where humanity will have to travel from one habitable planet to another every few millennia because of the limited timespan of habitability for each of these planets. I personally believe that for humanity to live forever, we will have to create a planet-like space ship that simply floats in space, away from stars, black holes, and anything else that may easily destroy the spaceship.
Who knows? There may even be a human-like creature on some of these planets out there in the universe that are writing a blog for their astronomy class and wondering if there are others like them out there.