Three large planets (between 5 and 17 Earth-masses) are known to exist around Gliese 581, a red dwarf star about 20 light years away.
Now a Swiss group has spotted a fourth planet around it. At just 1.9 Earth masses, it’s the smallest planet yet found around a main sequence star. It’s cool that we can confirm the presence of planets that are of similar size to ours.
Found at the nifty Dynamics of Cats.