The astronomers found these new planets using the "wobble" method. As a planet orbits its parent star, the gravity from the planet tugs slightly on the star. The result is that the planet and the star end up both orbiting their common gravitational center of mass. While the planet itself can be almost impossible to see, the wobble of the star is quite visible. This will even let you detect multiple planet systems. These stars, like our own Sun, are being pulled by the gravity of all their planets. This creates a complex motion within the star that can be dissected to infer where the planets are.
The really exciting thing about this discovery is not the method, but what they found. The team targeted low mass stars that had low metal content. Stars and their planets are formed out of the same disk of material. So, if a star has only a small amount of metal, you would expect planets to be an unlikely treat. They showed this is not the case. “These observations have given astronomers a great insight into the diversity of planetary systems and help us understand how they can form,” said research team member Nuno Santos. Many of these planets were also found just on the border of or inside of the region around the star called the habitable zone. This is where a planet could potentially have water on its surface, and, so the thinking goes, potentially life. This opens up a whole new class of stars that could be incubating distant life forms.
24 of the planets found have masses less than 20 times that of the earth. This is incredibly exciting. This gets us even closer to finding truly earth-sized planets, in the right spot around their host star to have life. As we refine our planet finding techniques, I expect that we will find smaller and smaller planets until we reach that long sought-after point. This study is exciting, because it does exactly what every good scientific study should. It has changed how we think about something we thought we understood and given us a exciting glimpse into what is to come.