The mystery of GJ 887d, the planet that may have liquid water on its surface (but it would take 17,000 years to reach it)

About 10.7 light-years from Earth, the existence of a potentially Earth-like exoplanet has been confirmed. It is called GJ 887d and, theoretically, it could maintain liquid water on its surface without being battered by violent stellar storms: two essential conditions for the possible development of life as we know it.

However, it remains an unreachable goal: even with the fastest object ever built, humanity would need over 17,000 years to reach it.

The celestial body was identified thanks to data from the Harps and Espresso spectrographs of the European Southern Observatory in Chile, and its confirmation is described in the journal Astronomy & Astrophysics by an international team coordinated by the Institute for Astrophysics and Geophysics of the University of Göttingen. Italy is involved through the Scuola Normale Superiore di Pisa.

"The planet discovered around the star GJ 887 was already identified in 2020, and now with the new data available, its existence has been confirmed," says astrophysicist Fabio Del Sordo from the Cosmology group of the Scuola Normale, who is also affiliated with the Catania Observatory of the National Institute of Astrophysics.

"The identified signal – he continues – shows that the planet moves on an orbit of about 50 days. It is very interesting also because it may have characteristics similar to those of planets in our Solar System. We are talking about a system that is not at astronomical distances, but only 6 light-years farther than Proxima Centauri, the closest star to Earth.

From the analysis, there is also evidence of another planet with an orbital period of just over 4 days and the trace of an additional candidate that completes its orbit in 2 days. The system could therefore include a total of 4 or 5 planets around a parent star classified as a red dwarf: cooler than the Sun and with a mass about half that of the Sun.

"It is an interesting star – notes Del Sordo – not only because it is one of the closest to our Sun, but also because it does not exhibit excessive production of stellar storms, or winds that inundate the planets orbiting around it with intense radiation, unlike, for example, Proxima Centauri", which "has an enormous magnetic activity that would not allow the presence of life".

As for potential habitability, "with the distance between GJ 887 and GJ 887d – it explains further – in theory, the presence of liquid water on the surface would be possible. All of this, of course, should be said with a big question mark": we do not "know the atmospheric composition and the real dimensions of the planet, we only know that it has a mass that is at least six times greater than that of Earth".

Nonetheless, "the fact remains that GJ 887d is one of the most interesting planets ever discovered precisely because, among those positioned in a habitable zone, it is the closest to our planet."