Exoplanet GJ 504b. Computer illustration of the newly discovered exoplanet GJ 504b (left), in orbit around its star GJ 504 (upper right), which lies around 57 light-years from Earth. Several times the mass of Jupiter and similar in size, this planet is the lowest-mass planet ever detected around a star like the Sun using direct imaging techniques. GJ 504b was discovered using the HiCiao instrument and AO188 adaptive optics system on the Subaru Telescope at the Mauna Kea Observatory, Hawaii.