GJ 887 d is the second-closest planet known to orbit within its star's habitable zone, after Proxima Centauri b. The habitable zone is the range of distances where a planet could keep liquid water on its surface, if it has a suitable atmosphere. GJ 887 d circles a bright red dwarf about 10.7 light-years away, once every 50.8 days.
It took six years to confirm. When the RedDots team announced two super-Earths around GJ 887 in 2020, they also saw a third signal at about 50 days, but could not tell whether it came from a planet or from the star itself. In 2026 a team led by C. Hartogh gathered 101 new measurements with the HARPS spectrograph and 12 with ESPRESSO, both operated by the European Southern Observatory, timed to test that signal. They used the radial velocity method, which finds planets from the slight back-and-forth motion their gravity gives the star, and modelled the star's own variations alongside it. The signal held up as a planet.
GJ 887 d is a super-Earth, heavier than Earth but lighter than Neptune, with a minimum mass of about six Earth masses. The same study confirmed a fourth planet, GJ 887 e, an Earth-mass world on a 4.4-day orbit, and found a further signal at 2.2 days that could be another small planet but might have other causes, so it remains a candidate.
Its habitability is an open question. The planet has never been seen crossing in front of its star, so its size, and therefore whether it is rocky or wrapped in thick gas, is not known. Only a minimum mass has been measured, and the true mass could be higher. In its favour, GJ 887 is an unusually quiet red dwarf whose brightness barely varies, which makes it more likely that a planet there could keep an atmosphere, and its brightness makes it a strong target for future telescopes.