Gliese-581d is one of five planets to be discovered orbiting red dwarf star Gliese 581. It is bigger than 581g, with a mass at least seven times Earth's and twice as big in size. The planet orbits ...

An astronomer born 100 years ago is coming into his own. This week, we celebrated the 100th birthday of Wilhelm Gliese — pronounced “Gleesa” — an obscure German astronomer. Over the next ...