3 The names of transiting planets
The first planet discovered by the WASP project was called WASP-1 b, the second was called WASP-2 b, and so on. In general, transiting exoplanets are named after the project that discovered them, and their host stars are renamed accordingly. So, the hyphen and number forms part of the new name for the star which hosts the exoplanet. Before its exoplanet was discovered, the star WASP-1 was known only by its catalogue number: GSC 02265-00107. WASP-1 b is a more memorable name for a planet than GSC 02265-00107 b!
As you’ve already seen with HD 209458 b, sometimes transiting planets are known simply by their star’s catalogue number. This is most likely to happen if the planet was discovered by radial velocity observations before the transits were detected. These examples follow the naming convention described in Week 3.