WASP-121b
| Artist's impression of WASP-121b and its host star | |
| Discovery | |
|---|---|
| Discovered by | L. Delrez et al. | 
| Discovery date | 2015 | 
| Transit | |
| Designations | |
| Tylos | |
| Orbital characteristics | |
| 0.02596+0.00043 −0.00063 AU | |
| Eccentricity | <0.0032 | 
| 1.27492504(15) d | |
| Inclination | 88.49°±0.16° | 
| 10°±10° | |
| Star | WASP-121 | 
| Physical characteristics | |
| 1.753±0.036 RJ | |
| Mass | 1.157±0.070 MJ | 
| Mean density | 0.266+0.024 −0.022 g/cm3 | 
| 9.33+0.71 −0.67 m/s2 (0.95 g) | |
| Temperature | 2602±53 K (2,329 °C; 4,224 °F) | 
WASP-121b, formally named Tylos, is an exoplanet orbiting the star WASP-121. WASP-121b is the first exoplanet found with an extrasolar planetary stratosphere (an atmospheric layer in which temperatures increase as the altitude increases) and the first that contains water. WASP-121b is in the constellation Puppis, and is about 858 light-years from Earth.