Pulled by this unseen planet, the star 51 Pegasi approaches and recedes from Earth every 4.2 days. The planet, a gas giant like our Jupiter or Saturn, is called 51 Peg b for its parent star. Its 4.2 day orbit is an orbit incredibly close for a gas planet and, as noted, most of the exoplanets so far found are large gas planets, with the exception of a few, like Gliese 581.

Theorists believed that, like Jupiter, giant gas planets would only be found far from their stars in orbits taking years to complete. But as astronomers have watched more stars, more gas planets have been turning up in extremely close orbits or on wildly eccentric paths, some in weirdly elongated orbits and others so close to their star that they circle it in days or even hours.

These worlds are called ROASTERS or ECCENTRIC GIANTS