The world is one of three tentatively identified new exoplanets orbiting the star HD 40307. The outermost planet, HD 40307 g, orbits comfortably in the habitable zone, where Earth-like temperatures are possible. That means HD 40307 g could have liquid water on the surface—a probable prerequisite for life. The research is in the journal Astronomy & Astrophysics.

But the planet is at least seven times as (massive) as Earth. So it could be a supersize version of our planet. Or it might be a scaled-down Neptune. A mini-Neptune would lack a solid surface and probably would not be an ideal habitat for life.

The star in question was already known to host three planets, so the total could reach six if the new finds are (independently) confirmed.

Confirmation is hardly assured. Two years ago some of the same astronomers involved in this work said they had located a potentially habitable planet called Gliese 581 g. But other researchers disputed the finding, and that planet's (existence) has been in limbo ever since. As usual, more data should settle the argument.