WASP-47

It was first noticed to have a hot Jupiter exoplanet orbiting every 4 days in 2012 by the Wide Angle Search for Planets (WASP) team.

When observed by NASA's K2 mission, it was given the Ecliptic Plane Input Catalog designation of EPIC 206103150, and later named K2-23 after the discovery of planets d and e. In 2012, a team from the SuperWASP group, led by Coel Hellier, announced the discovery of a Hot Jupiter exoplanet, with the designation WASP-47b, orbiting every 4.17 days.

[4] Three years later in 2015, Neveu-Van Malle et al. found a second planet, WASP-47c, orbiting within the habitable zone of the system using the HARPS spectrograph at the La Silla Observatory in Chile.

[7] The star is very metal-rich, with a metallicity ([Fe/H]) of about +0.36, or about twice the amount of iron and other elements heavier than Hydrogen and Helium than the Sun.

WASP-47e has almost no volatile materials (water, hydrogen/helium), d has a thin gaseous envelope, and b and c are both gas giants like Jupiter and Saturn.

In stark contrast to the inner planets, c has an eccentric orbit (e = 0.36) lasting over 580 days within the habitable zone of its host star.

The only likely remaining explanation is that another massive planet altered the orbit of WASP-47c that is either further out in the system or was ejected billions of years ago.