Gas giant
The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope.
Gliese 876
Gliese 876d, discovered in 2005, is the innermost known planet. With an estimated minimum mass only 5.88 times that of the Earth, it is possible that it is a dense terrestrial planet.Gliese 876 c, discovered in 2001, is a giant planet at 0.62 Jupiter-mass planet. It is in a 1:2 orbital resonance with the outermost known planet, taking 30.340 days to orbit the star. The planet orbits within the habitable zone. Its mass makes it more likely to be a Class II planet in the Sudarsky extrasolar planet classification. The presence of surface liquid water is possible on sufficiently massive satellites should they exist.Gliese 876 b, discovered in 1998 is around twice the mass of Jupiter and revolves around its star in an orbit taking approximately 61 days to complete, at a distance of only 0.208 AU, less than the distance from the Sun to Mercury. Its mass makes it more likely to be a Class II or Class III planet in the Sudarsky model. The presence of surface liquid water is possible on sufficiently massive satellites should they exist.Gliese 876 e, discovered in 2010, has a mass similar to that of the planet Uranus and its orbit takes 124 days to complete.