Hot Jupiters (also called roasters, epistellar jovians, pegasids or pegasean planets) are a class of extrasolar planets whose mass is close to or exceeds that of Jupiter (1.9 × 1027 kg), but unlike in the Solar System, where Jupiter orbits at 5 AU, the planets referred to as hot Jupiters orbit within approximately 0.05 AU of their parent stars, about one eighth the distance that Mercury orbits the Sun.
Hot Jupiters have some common characteristics:
Hot Jupiters are the easiest extrasolar planets to detect via the radial velocity method, because the oscillations they induce in their parent stars' motion are relatively large and rapid, compared to other known types of planets.
After hot Jupiters get their atmospheres stripped away, their cores may become chthonian planets.
Simulations have shown that the migration of a Jupiter-sized planet through the inner protoplanetary disk (the region between 5 and 0.1 AU from the star) is not as destructive as one might assume. More than 60% of the solid disk materials in that region are scattered outward, including planetesimals and protoplanets, allowing the planet-forming disk to reform in the gas giant's wake. In the simulation, planets up to 2 Earth masses were able to form in the habitable zone after the hot Jupiter passed through and its orbit stabilized at 0.1 AU. Due to the mixing of inner solar system material with outer solar system material from beyond the "snow line", simulations indicated that the terrestrial planets that formed after a hot Jupiter's passage would be particularly water-rich.